Compound system containing environmentally friendly flame retardant melamine phosphite, preparation method and application thereof

Abstract

The application relates to a compounded system containing environment-friendly flame retardant melamine phosphite, a preparation method and application thereof, and belongs to the technical field of flame retardants. In order to overcome the shortcomings and deficiencies in the prior art, a compounded system containing melamine phosphite is prepared by taking melamine, phosphorous acid and a modifier as raw materials. The application has the beneficial effects that: (1) the preparation method is simple in operation, low in production cost and easy for batch production; (2) the compounded system has the advantages of simultaneous flame-retardant effect of acid source, gas phase and condensed phase, corrosion resistance, low smoke, low toxicity, difficulty in moisture absorption and high temperature resistance; (3) the compounded system can be well dispersed in a matrix, has good flame-retardant performance and is not easy to precipitate; and (4) the compounded system containing melamine phosphite with different particle sizes is obtained through screening, so that the requirements of different high polymer products on particle sizes are met.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flame retardant, and particularly relates to a preparation method of a compound system containing melamine phosphite salt as an environmentally friendly flame retardant. BACKGROUND

[0002] Polymer materials occupy an increasingly important position in daily life and production due to their excellent properties, but the fire caused by flammability and low ignition point of the polymer materials brings heavy losses to people, so the research on polymer flame retardant materials is necessary. At present, in terms of global production and consumption, flame retardants have become plastic additives next to plasticizers. Due to the expansion of the application field of flame retardant materials and the demand of human survival environment, the research on new flame retardant synthesis and flame retardant technology with multiple flame retardant effects (gas phase, condensed phase flame retardant) and low smoke and low toxicity has become two major issues of the current polymer flame retardant materials.

[0003] Intense smoke during combustion of polyurethane material can cause suffocation and serious environmental pollution, but it is found that melamine has very good smoke suppression effect as a flame retardant and smoke suppressant for polyurethane. Phosphite is a new domestic inorganic phosphorus flame retardant, which has good dispersibility, good affinity with organic matrix, helps to play the excellent performance of organic materials, avoids material damage and failure caused by local stress, and has the advantages of stability, high expansion rate and better flame retardant effect compared with aluminum hypophosphite, and can be used as a flame retardant alone or in combination.

[0004] If melamine is used as an additive flame retardant for polyurethane foam, a large amount of melamine needs to be added to achieve good flame retardant effect, and a large amount of addition will inevitably affect the other properties of the polymer. Therefore, melamine is usually used in combination with other flame retardants. Liu Xinmin et al. used melamine as a flame retardant for polyurethane hard foam plastic in the development of polyurethane hard foam for composite boards. It was found that the use amount of melamine reached 50wt% and still did not meet the flame retardant requirements, but affected the compressive strength of the material. However, when melamine was used in combination with dimethyl methylphosphonate, trichloroethyl phosphate and other flame retardants, the use amount of 15% could meet the flame retardant requirements, indicating that melamine has a synergistic effect with other flame retardants. In addition, the thermal decomposition temperature of melamine is relatively low compared with the resin processing temperature, which can easily cause the decomposition of melamine during processing, and the flame retardant effect is also reduced. Phosphite mainly plays a flame-retardant role in acid source and condensed phase, and the amount of gas generated is small, so the flame-retardant effect in the gas phase is limited. SUMMARY

[0005] In order to overcome the shortcomings and deficiencies in the prior art, the present application uses melamine, phosphorous acid (and its salt) and a modifier as raw materials to prepare a compound system containing melamine phosphite salt.

[0006] The preparation method of the complex system containing the environmentally friendly flame retardant melamine phosphite specifically comprises the following steps:

[0007] (1) Synthesis of melamine phosphite:

[0008] a. Dissolve phosphorous acid in deionized water, start heating and stirring to obtain a phosphorous acid or its salt solution with a concentration of 30-50 wt%;

[0009] The concentration of the phosphorous acid solution in step a is 30-50%; the heating temperature is set at 70-80°C, and the stirring speed is 12-17 r / min.

[0010] b. Disperse melamine in an aqueous solution at a ratio of 30-50 wt%, then add 30-50 parts by weight of the melamine aqueous solution to the phosphorous acid solution in step a in batches, generally with each batch adding 10-17 g, and the batch addition can prevent agglomeration and ensure complete reaction, and each time the addition is continued after the solution becomes transparent, and the stirring is continued under heating conditions;

[0011] In step b, the melamine is dispersed in an aqueous solution to prevent agglomeration of the melamine, and the heating temperature is consistent with step a.

[0012] c. After about 1.5 h of reaction, add 1-5 parts by weight of a modifier, and continue stirring until the reaction is transparent, then stop;

[0013] The modifier includes but is not limited to stearic acid, silane coupling agent, titanate, Tween-80, and other mineral modifiers, and the concentration of the modifier is 1 wt%-5 wt%. The total reaction time is 1.5 h-3 h, preferably 3 h, and the modifier is added in the middle of the reaction.

[0014] d. After the reaction is complete, the obtained solution is completely cooled, then filtered and washed to neutral pH to obtain white precipitate;

[0015] e. Place the white precipitate in an oven and bake and dry to obtain a complex system containing melamine phosphite;

[0016] The baking temperature is 90°C-240°C, preferably 110°C, and the drying time is 2 h-8 h, preferably 5 h.

[0017] f. Control the content of crystalline water in the complex system containing melamine phosphite through the baking process;

[0018] The baking temperature in step f is 150°C-240°C, and the baking time is 3 h-8 h, and the temperature and time are adjusted according to different requirements for the content of crystalline water.

[0019] g.The product is ground and screened to obtain a complex system containing melamine phosphite with different particle sizes.

[0020] A complex system containing melamine phosphite prepared according to the preparation method.

[0021] The application also provides an application of the complex system containing melamine phosphite: the complex system containing melamine phosphite is used for efficacy verification, and thermal gravimetric experiments, combustion performance tests, glowing wire tests of products are carried out, and the influence of the complex system containing melamine phosphite on the mechanical properties of the products is investigated.

[0022] The complex system containing melamine phosphite is innovatively synthesized, and the complex system containing melamine phosphite simultaneously plays a flame-retardant role in an acid source, a gas phase and a condensed phase, and is used for improving the flame-retardant and thermal stability performance of melamine in polyurethane and the like.

[0023] In addition, the application also provides a use of the complex system containing melamine phosphite added into polypropylene, polystyrene, nylon 6 / 66, epoxy resin and other high molecular resins.

[0024] The application has the following advantages and effects relative to the prior art:

[0025] (1) The preparation of the complex system containing melamine phosphite is completed in one step, the preparation method is simple to operate, the production cost is low, and batch production is easy to realize.

[0026] (2) The complex system containing melamine phosphite prepared by the application has the advantages of simultaneously playing a flame-retardant role in an acid source, a gas phase and a condensed phase, corrosion resistance, low smoke, low toxicity, difficulty in moisture absorption and high temperature resistance and the like.

[0027] (3) In the preparation process, the modifier is added to improve the dispersion degree of the crystal, the complex system containing melamine phosphite can be well dispersed in the matrix as a high molecular flame-retardant additive, has good flame-retardant performance, and is not easy to precipitate.

[0028] (4) The complex system containing melamine phosphite prepared by the application is novel, and enriches the high polymer flame-retardant system.

[0029] (5) Different particle sizes of the complex system containing melamine phosphite are obtained through screening, and the requirements of different high molecular products for particle sizes are met. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A thermogravimetric test diagram of the complex system containing melamine phosphite;

[0031] Figure 2SEM images (a1 and a2) and photograph (a3) ​​of PAPP+MPP, a composite system containing melamine phosphite, after combustion of the sample added to PP material.

[0032] Figure 3 Particle size distribution diagram of the compound system containing melamine phosphite; Detailed Implementation Example

[0033] Weigh 70g of phosphorous acid and add it to a 1L round-bottom flask containing 200ml of deionized water. Place the flask in an oil bath and heat with stirring at 80℃. Weigh 70g of melamine and add it to 100ml of deionized water to disperse it. Then, add the melamine dispersion to the phosphorous acid mixture in batches, adding more as the solution becomes clear. Maintain the temperature of the mixture at 80℃ and continue stirring for 0.5h. Add 3g of silane coupling agent and continue stirring for 1h. The time to transparency gradually increases, and the suspension gradually becomes viscous. Add water and raise the temperature to 100℃. The reaction is complete when the solution becomes clear. After the mixture has completely cooled, filter and repeatedly wash the precipitate until the pH is neutral to obtain a white precipitate. Place the precipitate in an oven at 90℃ for 8h, then adjust the baking temperature to 150℃ and bake for 2h to obtain a compound system containing melamine phosphite with a moisture content of 3%. The compound system containing melamine phosphite was ground and sieved to obtain a product with a particle size D50 of 3-7 micrometers.

[0034] As a compound flame retardant, in halogen-free flame-retardant PP (PAPP system), the addition of PAPP+MPP, which replaces a portion of the melamine phosphite compound system, to the PP material achieves UL94 (V0) flame retardancy. The flame retardant performance tests before and after compounding are shown in Table 1 below:

[0035]

[0036] Afterflame time (T1+T2 / S): The duration of the afterflame;

[0037] LOI: Limiting Oxygen Index. A high index indicates that the material is not easily combustible, while a low index indicates that the material is easily combustible. Generally, an oxygen index <22% is considered a flammable material, an oxygen index between 22% and 27% is considered a combustible material, and an oxygen index >27% is considered a flame-retardant material.

[0038] UL94 flame retardancy rating V0 for plastics: After two 10-second burning tests on the sample, the flame extinguishes within 30 seconds. No burning material should fall.

[0039] From the test data in Table 1, it can be seen that the limiting oxygen index of the PP material to which the melamine phosphite-containing complex system is added to replace part of PAPP+MPP is increased from 28% to 29%, the flammability of the material is reduced, the horizontal afterflame burning time is increased by 1 second, and the flame retardant grade UL94 reaches V0 level.

[0040] Figure 1 The thermal gravimetric test graph of the melamine phosphite-containing complex system of Example 1 is shown. It can be seen from the graph that decomposition starts at 260°C, and a large amount of decomposition occurs in the interval of 500°C, producing phosphates and non-flammable ammonia substances and gases.

[0041] Figure 2 The SEM test graph (a1 and a2) and the photo (a3) after burning of the sample of the PP material to which the melamine phosphite-containing complex system of Example 1 is added to replace part of PAPP+MPP. According to the SEM of the residue after burning of the sample, it can be seen that during the burning process, the flame retardant forms a porous protective layer in the condensed phase and the carbon residue layer, and at the same time plays a flame-retardant role in the gas phase and the condensed phase, preventing the contact of oxygen with the combustible material. The flame-retardant mechanism analysis is as follows: during burning, phosphoric acid will further dehydrate to form metaphosphoric acid, and metaphosphoric acid will further polymerize to form poly-metaphosphoric acid. In this process, not only does the covering layer generated from phosphoric acid play a covering effect, but also poly-metaphosphoric acid, which is a strong acid and a very strong dehydrating agent, will cause the polymer to dehydrate and carbonize, change the mode of the polymer burning process and form a carbon film on its surface to isolate air, and the non-flammable gases such as ammonia and water vapor generated by decomposition not only dilute the concentration of oxygen and combustible materials in the gas phase, but also capture hydrogen atom radicals in the flame to inhibit the burning process, thereby playing a stronger flame-retardant effect. It can be proved that the flame-retardant mechanism of the product is mainly the synergistic flame-retardant effect of acid source, condensed phase and gas phase, which is an intumescent flame retardant system.

[0042] Figure 3 The graph in FIG. 1 shows the particle size of the melamine phosphite-containing complex system with different contents of the modifier. The particle size of the melamine phosphite-containing complex system without modification and the particle size of the melamine phosphite-containing complex system with 1%-5% of the modifier are as follows: Figure 3 as shown in the graph in FIG. 1, Figure 3 The corresponding samples are shown in Table 2 below:

[0043]

[0044] Table 2

[0045] The D50 and D97 data of the particle size of the melamine phosphite-containing complex system with different amounts of modifier show that after adding the modifier, the particle size of the melamine phosphite-containing complex system is significantly reduced: the D50 is reduced from 6.2 μm to 3.6-4.6 μm, and the particle size distribution is more uniform: the D97 is reduced from 31 μm to 15-22 μm. Among them, when the content of the modifier is 3%, the particle size is the smallest, and the particle size distribution is the most uniform. The above data show that the modifier can control the particle size of the crystal of the melamine phosphite-containing complex system to improve its dispersibility, and the smaller the particle size and the more uniform the distribution, the better the dispersibility of the crystal. Examples

[0046] 50 g of phosphorous acid was weighed into a 1 L round-bottom flask containing 150 ml of deionized water, and the round-bottom flask was placed in an oil bath with heating and stirring, and the temperature was controlled at 80°C. 50 g of melamine was weighed, dispersed in 80 ml of deionized water, and then added to the phosphorous acid mixture in batches, with each addition being followed by stirring until the solution became transparent. The temperature of the mixture was maintained at 80°C and stirring was continued for 0.5 h. 3 g of sodium stearate was added and stirring was continued for 1 h. The transparent time gradually increased and the suspension gradually became viscous. The water was replenished and the temperature was increased to 100°C. The reaction was terminated when the mixture became transparent. After the mixture was completely cooled, it was filtered and the precipitate was washed repeatedly until the pH was neutral. A white precipitate was obtained. The precipitate was placed in an oven at 80°C for 8 h, and then the temperature was adjusted to 110°C for 5 h to obtain a melamine phosphite-containing complex system with a water content of 2%. The melamine phosphite-containing complex system was ground and sieved to obtain a product with a particle size D50 of 3-7 μm.

[0047] As a complex flame retardant, part of the PAPP was replaced by the melamine phosphite-containing complex system in the halogen-free flame-retardant PP (PAPP system) and added to the PP material to achieve UL94 (V0) flame retardation. The flame-retardant performance test results before and after the complexation are shown in Table 3.

[0048]

[0049] As shown by the test data in Table 3, the replacement of part of the PAPP by the melamine phosphite-containing complex system in the PP material increased the limiting oxygen index from 28% to 30.4%, significantly increased the flame resistance of the material, and increased the vertical and horizontal afterflame burning time by 1 second, with the flame retardation level UL94 reaching V0 level.

[0050]

[0051] Table 4

[0052] Table 4 is the mechanical property test data of the complex system containing melamine phosphite in halogen-free flame-retardant PP (PAPP system). From the data in the table, compared with the original flame-retardant formula of halogen-free flame-retardant PP, after replacing part of PAPP with MEOP, the tensile strength and bending strength and modulus of the PP material are slightly reduced, the elongation at break representing the toughness index is increased by 100%, and the notched impact strength is also slightly increased.

Claims

1. Process for the preparation of a complex system comprising the environmentally friendly flame retardant melamine phosphite, characterized in that, The preparation method comprises the following steps: a. Dissolve phosphorous acid in deionized water, start heating and stirring to obtain a 30-50wt% phosphorous acid solution; b. Disperse melamine in water to obtain a 30-50wt% melamine aqueous solution, then add 30-50 parts by weight of the melamine aqueous solution into the solution of step a in batches, and continue stirring and heating; c. Add a modifier in the middle of the reaction, continue stirring until the reaction is transparent, and then stop the reaction, wherein the modifier is a silane coupling agent, and the concentration of the modifier is 1-5wt%; d. After the reaction is completed, the obtained solution is completely cooled, then filtered and washed to neutral pH to obtain white precipitate; e. Place the white precipitate in an oven, bake and dry to obtain a melamine phosphite-containing compound system.

2. A process for the preparation of a formulation comprising the environmentally friendly flame retardant melamine phosphite salt according to claim 1, characterized in that, The heating temperature in step a is set at 70-80℃.

3. A process for the preparation of a formulation comprising the environmentally friendly flame retardant melamine phosphite salt according to claim 1, characterized in that, The baking temperature in step e is 90-240℃, and the drying time is 2-8h.

4. A process for the preparation of a formulation comprising the environmentally friendly flame retardant melamine phosphite salt according to claim 3, characterized in that, The baking temperature in step e is 110℃, and the drying time is 5h.

5. A process for the preparation of a formulation comprising the environmentally friendly flame retardant melamine phosphite salt according to claim 1, characterized in that, The preparation method further comprises the following steps: f. Control the content of crystal water in the melamine phosphite-containing compound system through a baking process, and the baking temperature is 150-240℃; g. Grind and sieve to obtain a melamine phosphite-containing compound system with different particle sizes.

6. The melamine phosphite-containing compound system prepared by the preparation method of claim 1-5.

7. Use of a melamine phosphite containing complex system prepared according to the method of claim 6, characterized in that, The melamine phosphite-containing compound system is added as a flame retardant to polypropylene, polystyrene, nylon 6 / 66 and epoxy resin high molecular resins.

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