Production method of modified organophosphorus flame retardant for polypropylene

Abstract

The invention discloses a production method of a modified organophosphorus flame retardant for polypropylene. The production method comprises the following steps: mixing tetrabutyl titanate and absolute ethyl alcohol to form an ester-alcohol mixed solution; adding calcium carbonate into the agar aqueous solution to form a calcium agar solution; dropwise adding the calcium agar solution into the ester-alcohol mixed solution, keeping stirring, reacting and aging, filtering after aging to obtain a water-containing colloid, and performing heat treatment dehydration and crushing on the water-containing colloid to obtain a titanium dioxide inclusion; roasting the titanium dioxide inclusion, cooling and then washing to obtain calcium titanate particles; heating and melting a solid low-melting-point organophosphorus flame retardant, and dipping the molten organophosphorus flame retardant into the calcium titanate particles to form flame retardant particles; and carrying out coupling agent modification on the flame retardant particles to obtain the flame retardant. By utilizing the adsorbability of pores in calcium titanate, the volatility of the organic phosphorus flame retardant during polypropylene plastic processing is reduced, so that the heat resistance of the polypropylene plastic is improved, and the migration ability of the polypropylene plastic is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to a production method of modified organic phosphorus flame retardant, in particular to a production method of modified organic phosphorus flame retardant for polypropylene. BACKGROUND

[0002] In order to reduce the flammability of polypropylene plastic, it is necessary to add flame retardant to it to meet the flame retardant needs of polypropylene plastic in various industries. The traditional halogen-based flame retardant is limited in application due to its toxicity and the production of toxic gases such as dioxin during combustion.

[0003] Phosphorus-based flame retardants have become the main substitutes for halogen-based flame retardants. Existing phosphorus-based flame retardants are mainly divided into two categories: inorganic phosphorus-based flame retardants and organic phosphorus-based flame retardants. Among them, inorganic phosphorus-based flame retardants mainly include red phosphorus flame retardant, ammonium phosphate salt, ammonium polyphosphate, etc. Although inorganic phosphorus-based flame retardants have the advantages of good thermal stability, non-volatility and long-lasting effect, their use is greatly limited due to the large amount of addition.

[0004] Although organic phosphorus-based flame retardants also have the disadvantage of poor flame retardant performance, they have been widely used due to their relatively low addition amount. However, since they are in liquid state and have an oily appearance, they are not easy to add during the processing of polypropylene plastic. In addition, due to their low melting point, they have the problems of high volatility, poor heat resistance, easy migration, etc. Therefore, improving the addability of low-melting-point organic phosphorus-based flame retardants during the processing of polypropylene plastic will be beneficial to the popularization and use of organic phosphorus-based flame retardants. SUMMARY

[0005] In order to improve the addability of low-melting-point organic phosphorus-based flame retardants during the processing of polypropylene plastic, the present application provides a production method of modified organic phosphorus flame retardant for polypropylene, which comprises the following steps:

[0006] (1) uniformly mix tetrabutyl titanate and anhydrous ethanol to form an ester-alcohol mixture;

[0007] (2) dissolve agar in boiling water to form an agar aqueous solution with a concentration of 1-1.5wt%, keep the agar aqueous solution at 45-60℃, and add calcium carbonate into the agar aqueous solution, stir uniformly to form an agar calcium solution with a calcium carbonate concentration of 4-5wt%;

[0008] (3) at 45-60℃, drop the agar calcium solution into the ester-alcohol mixture, keep stirring, react for 0.5-1h, then age, after aging, reduce the reaction liquid to room temperature, filter the reaction liquid to obtain a water-containing colloid, then perform heat treatment and dehydration on the water-containing colloid and crush it to obtain a titanium dioxide coating body, which is calcium carbonate powder coated with titanium dioxide on the surface;

[0009] (4) calcining the titanium dioxide coated body, and washing after cooling to obtain calcium titanate microparticles;

[0010] (5) heating and melting the solid low-melting organic phosphorus flame retardant into a liquid flame retardant, then immersing the calcium titanate microparticles into the liquid flame retardant, filtering while hot after the immersion to form flame retardant microparticles;

[0011] (6) modifying the flame retardant microparticles with a modifier to obtain.

[0012] Specifically, the solid low-melting organic phosphorus flame retardant is at least one of TPP and RDX. Preferably, calcium carbonate powder with a particle size of 1250-2000 mesh is used.

[0013] When washing the calcined titanium dioxide coated body, distilled water or cold dilute hydrochloric acid can be used. In this application, the tetrabutyl titanate and ethanol in the ester alcohol mixture form a chelate. When the agar calcium solution is added to the ester alcohol mixture, the agar calcium solution is dispersed into agar balls coated with calcium carbonate ions under strong stirring.

[0014] Due to the excess ethanol in the ester alcohol mixture, the water in the agar calcium solution can be absorbed, which causes the volume of the agar balls to shrink, but the agar still retains a large amount of water, which can hydrolyze the surrounding chelate to form titanium dioxide. When the concentration of the chelate around the calcium carbonate decreases, the surrounding chelate will automatically replenish to maintain the concentration, thereby forming a titanium dioxide shell on the surface of the calcium carbonate. During the subsequent calcination process, the calcium carbonate reacts with the titanium dioxide to form calcium titanate, and at the same time, due to the high-temperature decomposition of the calcium carbonate, the generated carbon dioxide diffuses outward, forming a large number of pores in the interior of the calcium titanate, which are used to absorb and store organic phosphorus flame retardants.

[0015] Due to the coupling agent modification on the surface of the calcium titanate, the compatibility with polypropylene ions is effectively improved, the addability is improved, thereby improving the uniformity of the distribution of the organic phosphorus flame retardant in the polypropylene plastic, and simultaneously improving the uniformity of the flame retardance of the polypropylene plastic. The adsorption of the pores in the calcium titanate reduces the volatility of the organic phosphorus flame retardant during the processing of the polypropylene plastic, thereby improving the heat resistance and reducing the migration ability.

[0016] When calcination is performed, the outside of the calcium carbonate particles first reacts with the external titanium dioxide, which hinders the continued reaction of the internal calcium carbonate, resulting in some of the material forming calcium titanate particles wrapped with calcium oxide after the completion of calcination, the calcium oxide being removed in the subsequent washing process, forming a small cavity in the interior of the calcium titanate microparticles to increase the adsorption amount of the flame retardant. During calcination, due to the hindrance of the first formation of calcium titanate, some of the external titanium dioxide remains in its original state, so that the formed calcium titanate microparticles are actually a mixture of calcium titanate and titanium dioxide.

[0017] Specifically, in step (1), the mass ratio of tetrabutyl titanate to anhydrous ethanol is 1:(3-5). Under the above ratio, not only can the alcoholization of tetrabutyl titanate be ensured, but also the water in the aqueous agar solution can be adsorbed to reduce the radius of the agar calcium ions, so that the adsorbed titanium dioxide ions are closer to the calcium carbonate particles, so that in the subsequent calcination process, calcium titanate can be smoothly generated. The unreacted titanium dioxide can improve the uniformity of the dispersion of the flame retardant microparticles in the plastic.

[0018] Further, to ensure the amount of calcium titanate generated, in step (3), the mass ratio of calcium carbonate to tetrabutyl titanate is 1:(6-8). Under the above ratio of calcium carbonate to tetrabutyl titanate, the ratio of the generated titanium dioxide to calcium carbonate exceeds 1:1, so that there is sufficient titanium dioxide on the surface of the calcium carbonate, avoiding a decrease in the amount of calcium titanate generated due to a low content of titanium dioxide in some areas.

[0019] Further, to enable the tetrabutyl titanate in the solution to fully react and improve the uniformity of the distribution of titanium dioxide, in step (3), the aging reaction time is 20-40h.

[0020] Further, to fully remove the water in the water-containing colloid, in step (3), when the water-containing colloid is subjected to heat treatment for dehydration, the temperature is 150-250℃ and the time is 0.5-1h. If dehydration is insufficient, a large amount of water vapor will be generated during calcination, resulting in an excessively large inner diameter of the pores in the calcium titanate microparticles, which reduces the adsorption force of the flame retardant and affects the adsorption amount of the flame retardant.

[0021] Specifically, to ensure the smooth generation of calcium titanate during calcination, in step (4), when the titanium dioxide wrapper is calcined, the calcination temperature is 1000-1200℃ and the calcination time is 2-3h.

[0022] Specifically, to enable the flame retardant to be smoothly adsorbed onto the calcium titanate microparticles and reduce the adsorption time, in step (5), the impregnation is performed under vacuum, and the vacuum degree is 50-200Pa absolute pressure.

[0023] Specifically, in step (6), when the coupling agent modification is performed, the modifier is composed of materials in the following volume ratio: 50-70% deionized water, 20-40% anhydrous ethanol, 1-5% glacial acetic acid, and 1-5% silane coupling agent, and the mass ratio of the silane coupling agent to tetrabutyl titanate is (1-2): 100. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is an SEM image of the calcium titanate microparticles obtained in Example 1.

[0025] Figure 2 is an x-ray diffraction pattern of the calcium titanate microparticles obtained in Example 1. DETAILED DESCRIPTION

[0026] Example 1

[0027] 1# Production of modified organic phosphorus flame retardant:

[0028] (1) 5 g of tetrabutyl titanate and 20 g of anhydrous ethanol are uniformly mixed to form an ester-alcohol mixture;

[0029] (2) 0.15 g of agar is dissolved in 14.85 g of boiling water to form an agar aqueous solution with a concentration of 1 wt%, the agar aqueous solution is kept at 50°C, 0.75 g of calcium carbonate is added to the agar aqueous solution and stirred uniformly to form a calcium carbonate agar solution with a concentration of 4.76 wt%, and the particle size of the calcium carbonate is 1250 mesh.

[0030] (3) The calcium carbonate agar solution is added dropwise to the ester-alcohol mixture at 50°C, the stirring speed is kept at 1000 RPM, the reaction is carried out for 0.6 h, the reaction liquid is aged for 24 h, then the reaction liquid is cooled to room temperature, the reaction liquid is filtered to obtain a hydrous colloid, the hydrous colloid is heat treated at 150°C for 1 h, then the hydrous colloid is broken to obtain titanium dioxide coated bodies, and the titanium dioxide coated bodies are calcium carbonate powder coated with titanium dioxide;

[0031] (4) The titanium dioxide coated bodies are calcined at 1100°C for 3 h, then washed with distilled water to remove unreacted calcium oxide, and 1.47 g of calcium titanate microparticles are obtained; the calcium carbonate microparticles are detected to obtain the SEM image shown in FIG. 1 and the x-ray diffraction pattern shown in FIG. 2. Figure 1 Figure 2

[0032] (5) The TPP is heated and melted to form a liquid flame retardant, then the calcium titanate microparticles are immersed in the liquid flame retardant, after the immersion is completed, the flame retardant microparticles are formed by hot filtration, and the immersion is carried out in a vacuum state at an absolute pressure of 110 Pa. The content of TPP in the flame retardant microparticles is 44 wt%.

[0033] ​​(6) The flame retardant microparticles are modified by a coupling agent. The modifier is composed of the following materials in volume ratio: 50% deionized water, 20% anhydrous ethanol, 5% glacial acetic acid, and 5% silane coupling agent (KH550). The mass ratio of silane coupling agent to tetrabutyl titanate in the modifier is 1:100.

[0034] Example 2

[0035] 2# Production of modified organic phosphorus flame retardant:

[0036] (1) 5g of tetrabutyl titanate and 15g of anhydrous ethanol are uniformly mixed to form an ester-alcohol mixture;

[0037] (2) 0.225g of agar is dissolved in 14.775g of boiling water to form an agar aqueous solution with a concentration of 1wt%. The agar aqueous solution is kept at 55°C. 0.63g of calcium carbonate is added to the agar aqueous solution and stirred uniformly to form a calcium carbonate solution with a concentration of 4.03wt%. The particle size of the calcium carbonate is 2000 mesh.

[0038] (3) The calcium carbonate solution is added dropwise to the ester-alcohol mixture at 55°C, and the stirring speed is kept at 800RPM. After 1h of reaction, the reaction liquid is aged for 30h, then cooled to room temperature. The reaction liquid is filtered to obtain a water-containing colloid. The water-containing colloid is heat-treated at 200°C for 0.8h, then broken to obtain titanium dioxide-coated bodies, which are calcium carbonate powder coated with titanium dioxide on the surface;

[0039] (4) The titanium dioxide-coated bodies are calcined at 1000°C for 2.5h, then washed with distilled water to remove unreacted calcium oxide, and 1.45g of calcium titanate microparticles are obtained;

[0040] (5) The TPP is heated and melted to form a liquid flame retardant. Then the calcium titanate microparticles are immersed in the liquid flame retardant. After the immersion is completed, the flame retardant microparticles are filtered while hot. The immersion is carried out in a vacuum state at an absolute pressure of 80Pa. The content of TPP in the flame retardant microparticles is 43wt%.

[0041] (6) The flame retardant microparticles are modified by a coupling agent. The modifier is composed of the following materials in volume ratio: 70% deionized water, 25% anhydrous ethanol, 2% glacial acetic acid, and 3% silane coupling agent (KH550). The mass ratio of silane coupling agent to tetrabutyl titanate in the modifier is 2:100.

[0042] Example 3

[0043] 3# Production of modified organic phosphorus flame retardant:

[0044] (1) 5g of tetrabutyl titanate and 25g of anhydrous ethanol are uniformly mixed to form an ester-alcohol mixture;

[0045] (2) 0.195 g agar was dissolved in 14.805 g boiling water to form an agar solution with a concentration of 1.3 wt%, the agar solution was kept at 60 °C, 0.71 g calcium carbonate was added into the agar solution and stirred uniformly to form a calcium carbonate agar solution with a concentration of 4.52 wt% of calcium carbonate, the particle size of the calcium carbonate was 1250 mesh.

[0046] (3) The calcium carbonate agar solution was added dropwise into the ester alcohol mixture at 60 °C, the stirring speed was kept at 900 RPM, after 1 h of reaction and 40 h of aging, the reaction liquid was cooled to room temperature, the reaction liquid was filtered to obtain a hydrogel, the hydrogel was heat treated at 250 °C for 0.6 h and then broken to obtain titanium dioxide coated bodies, the titanium dioxide coated bodies were calcium carbonate powders coated with titanium dioxide on the surface;

[0047] (4) The titanium dioxide coated bodies were calcined at 1200 °C for 2 h, and then washed with distilled water to remove unreacted calcium oxide, 1.46 g of calcium titanate microparticles were obtained;

[0048] (5) RDX was heated and melted to form a liquid flame retardant, then the calcium titanate microparticles were added into the liquid flame retardant for impregnation, after impregnation, the flame retardant microparticles were formed by hot filtration, the impregnation was carried out under vacuum at an absolute pressure of 90 Pa. The content of RDX in the flame retardant microparticles was 45 wt%.

[0049] (6) The flame retardant microparticles were modified with a coupling agent, the modifier was composed of the following materials in volume ratio: 60% deionized water, 35% anhydrous ethanol, 1% glacial acetic acid and 4% silane coupling agent (KH550), the mass ratio of silane coupling agent to tetrabutyl titanate in the modifier was 1.4:100.

[0050] Comparative Example 1

[0051] 4# Production of modified organic phosphorus flame retardant: this comparative example was based on Example 1;

[0052] (1) 5 g of tetrabutyl titanate and 20 g of anhydrous ethanol were mixed uniformly to form an ester alcohol mixture;

[0053] (2) 0.75 g of calcium carbonate was added into 15 g of hot water with a temperature of 50 °C and stirred uniformly to form a calcium carbonate solution with a concentration of 4.76 wt% of calcium carbonate, the particle size of the calcium carbonate was 1250 mesh.

[0054] (3) at 50°C, the calcium carbonate solution is added dropwise into the ester alcohol mixture, keeping the stirring speed at 1000 RPM, after 0.6h reaction, the reaction solution is aged for 24h, then the reaction solution is filtered to obtain the water-containing gel, the water-containing gel is treated at 150°C for 1h, then broken to obtain the titanium dioxide coated body, which is the calcium carbonate powder coated with titanium dioxide on the surface;

[0055] (4) the titanium dioxide coated body is calcined at 1100°C for 3h, then washed with distilled water to remove the unreacted calcium oxide, to obtain 1.46g of calcium titanate microparticles;

[0056] (5) the TPP is heated to melt into liquid flame retardant, then the calcium titanate microparticles are immersed into the liquid flame retardant, after the immersion, the flame retardant microparticles are formed by hot filtration. The immersion is carried out under vacuum at 110Pa absolute pressure. The content of TPP in the flame retardant microparticles is 35wt%.

[0057] (6) the flame retardant microparticles are modified by coupling agent, the modifier is composed of the following materials in volume ratio: 50% deionized water, 20% anhydrous ethanol, 5% glacial acetic acid and 5% silane coupling agent (KH550), the mass ratio of silane coupling agent to tetrabutyl titanate in the modifier is 1:100.

[0058] From the comparative example, it can be seen that the content of organic phosphorus flame retardant in the flame retardant microparticles is reduced after the agar is removed, which indicates that the agar can increase the volume of calcium titanate microparticles and can adsorb more organic phosphorus flame retardant.

[0059] Comparative Example 2

[0060] 5# Production of modified organic phosphorus flame retardant: the comparative example is basically the same as Example 1, the only difference is that in step (2), the amount of calcium carbonate added is 2g. The content of TPP in the flame retardant microparticles is 42wt%.

[0061] Comparative Example 3

[0062] 6# Production of modified organic phosphorus flame retardant: the comparative example is basically the same as Example 1, the only difference is that in step (2), the amount of calcium carbonate added is 0.5g. The content of TPP in the flame retardant microparticles is 30wt%.

[0063] Comparative Example 4

[0064] 7# Production of modified organic phosphorus flame retardant: the comparative example is basically the same as Example 1, the only difference is that in step (3), the water-containing gel is not treated by heat to remove water and broken. The content of TPP in the flame retardant microparticles is 38wt%.

[0065] The flame retardant prepared in the above examples and the base material were mixed uniformly by a high-speed mixer according to the formulations shown in Table 1, and then were added into a twin-screw extruder for melt extrusion (the melt extrusion temperature was 200°C) and cooling and granulation to obtain a flame retardant composite, after which a test sample was prepared by an injection molding machine, and the limiting oxygen index and combustion grade were tested, and the results are shown in Table 1. In Table 1, the addition amount of each flame retardant is converted into pure organic phosphorus flame retardant, and does not include the weight of calcium titanate particles and coupling agent.

[0066] Table 1

[0067]

[0068] As can be seen from the results in Table 1, when the modified organic phosphorus flame retardant provided by the present application is used, the addition amount is 6-8wt%, and the combustion grade can reach V-0 grade, while the addition amount of TPP and RDX is 14wt% and 11wt% respectively to reach the same combustion grade. Therefore, the use amount of the flame retardant prepared in the present application can be reduced, which indicates that the modified organic phosphorus flame retardant prepared in the present application can effectively reduce the volatilization amount of the flame retardant during the processing of polypropylene plastic, and can effectively play its flame-retardant effect.

[0069] When the flame retardants prepared in Comparative Examples 1-4 are used, although the amount is lower than that of conventional organic phosphorus flame retardants, the amount is still high, which indicates that the flame retardant particles prepared by agar can reduce the loss amount of the flame retardant during the processing of plastic, and after the coupling agent is used for treatment, the addability of the flame retardant in plastic can be improved.

Claims

1. A method for producing a modified organophosphorus flame retardant for polypropylene, characterized by, It comprises the following steps: (1) uniformly mixing tetrabutyl titanate and anhydrous ethanol to form an ester-alcohol mixture; (2) dissolving agar in boiling water to form an agar aqueous solution with a concentration of 1-1.5wt%, keeping the agar aqueous solution at 45-60℃, adding calcium carbonate into the agar aqueous solution, and stirring to form a calcium carbonate solution with a concentration of 4-5wt% in agar; (3) at 45-60℃, adding the calcium carbonate solution in agar into the ester-alcohol mixture, keeping the stirring speed at 800-1000RPM, and reacting for 0.5-1h, then aging, lowering the reaction solution to room temperature, filtering the reaction solution to obtain a hydrous colloid, and then performing heat treatment on the hydrous colloid to dehydrate and crush the hydrous colloid to obtain titanium dioxide-coated bodies, which are calcium carbonate powders coated with titanium dioxide on the surface; (4) performing calcination on the titanium dioxide-coated bodies, and then washing and cooling the titanium dioxide-coated bodies to obtain calcium titanate microparticles; (5) heating and melting a solid low-melting-point organic phosphorus flame retardant to form a liquid flame retardant, then immersing the calcium titanate microparticles into the liquid flame retardant, filtering the calcium titanate microparticles while hot to form flame retardant microparticles; (6) performing coupling agent modification on the flame retardant microparticles using a modifier to obtain a modified product.

2. The production method according to claim 1, characterized by, In step (1), the mass ratio of tetrabutyl titanate to anhydrous ethanol is 1:(3-5).

3. The production method according to claim 1, characterized by, In step (3), the mass ratio of calcium carbonate to tetrabutyl titanate is 1:(6-8).

4. The production method according to claim 1, characterized by, In step (3), the aging reaction time is 20-40h.

5. The production method according to claim 1, characterized by, In step (3), when performing heat treatment on the hydrous colloid to dehydrate, the temperature is 150-250℃, and the time is 0.5-1h.

6. The production method according to claim 1, characterized by, In step (4), when performing calcination on the titanium dioxide-coated bodies, the calcination temperature is 1000-1200℃, and the calcination time is 2-3h.

7. The production method according to claim 1, characterized by, In step (5), the immersion is performed in a vacuum state, and the vacuum degree is 50-200Pa.

8. The production method according to claim 1, characterized by, In step (6), when performing coupling agent modification, the modifier is composed of the following materials in the following volume ratio: 50-70% deionized water, 20-40% anhydrous ethanol, 1-5% glacial acetic acid, and 1-5% silane coupling agent, and the mass ratio of the silane coupling agent to tetrabutyl titanate is (1-2):

100.

9. The production method according to claim 1, characterized by, The solid low-melting-point organic phosphorus flame retardant is at least one of TPP and RDX.

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