A synthetic method for regulating the crystal orientation of melamine cyanurate

Abstract

The present invention provides a synthesis method for regulating the crystal plane orientation of melamine cyanurate. The present invention adds melamine, a dispersant, a solvent and a pH regulator into a reactor, and stirs at a high speed at a certain temperature to obtain a highly dispersed ME precursor solution; then, cyanuric acid is added to the ME precursor solution, and after stirring at the reaction temperature for a period of time, a crystal plane inducing agent is added, and the stirring is continued for constant temperature reaction. After the reaction is completed, suction filtration, washing, drying and crushing are performed to obtain MCA with a specific crystal plane orientation. The present invention can suppress (110) and (200) crystal planes, induce (220) crystal plane growth, and interfere with the formation of a large-plane hydrogen bond network of MCA by adding a crystal plane inducing agent, and limit the unlimited expansion of the hydrogen bond network, thereby reducing the viscosity of the system. In addition, the MCA synthesized by the present invention has the characteristics of good dispersibility, high thermal stability, excellent flame retardancy, and can significantly improve the compatibility of MCA with polymers.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant materials, and in particular to a synthesis method for regulating the crystal plane orientation of melamine cyanurate. Background Art

[0002] Melamine cyanurate (MCA) is a triazine ring molecular complex formed by melamine and cyanuric acid through a large planar hydrogen bond network. MCA has been widely used in polymers, especially polyamide flame retardant due to its advantages such as high nitrogen content, low smoke, high flame retardant efficiency, and halogen-free. However, due to the poor dispersibility, easy agglomeration, and poor interface of MCA, its flame retardant efficiency in composite materials is reduced, and it cannot achieve good interface bonding with polymers, further causing the mechanical properties of polymers to decrease, limiting its application. Therefore, the synthesis of MCA with high dispersibility and good compatibility has great practical application value and significance.

[0003] Zeolite imidazolate framework (ZIF) is a zeolite-like structure material synthesized by coordination of Zn(I) or Co(II) with imidazole, also known as inorganic-organic hybrid material. ZIF materials have the advantages of high thermal stability, strong designability, good compatibility with polymers and abundant pores, so they have attracted extensive attention from researchers at home and abroad. At present, most studies are to improve the thermal stability, dispersibility and compatibility of MCA by simply adding modifiers during the synthesis of MCA.

[0004] The invention patent with application number CN201911350478.6 discloses a preparation method of melamine cyanurate (MCA) flame retardant and its application in PA6. The patent improves its compatibility and reduces the viscosity of the reaction system by adding surfactants and antimony trioxide during the synthesis process of MCA, but the RoHS directive limits antimony trioxide, and antimony trioxide is an inorganic flame retardant with poor compatibility with polymers. The invention patent with application number CN202110959156.2 discloses a modified MCA flame retardant and its preparation method. The patent adds fumed silica, graphene oxide, and red phosphorus to improve the mechanical properties and flame retardancy of the polymer, but has defects such as high cost, complex added ingredients, and many inorganic ingredients. The present invention improves the compatibility of MCA and polymer by adding a crystal face inducing agent, inhibits (110) and (200) crystal faces, induces the growth of (220) crystal face, and the unsaturated metal center on the surface of the crystal face inducing agent can coordinate with cyanuric acid, interferes with the formation of a large-plane hydrogen bond network of MCA, limits the unlimited expansion of the hydrogen bond network, and thus reduces the viscosity of the system. At the same time, the synthesized MCA has the characteristics of good dispersibility, high thermal stability, excellent flame retardancy, and can significantly improve the compatibility of MCA and polymers. Summary of the invention

[0005] In view of this, the present invention provides a synthesis method for regulating the crystal plane orientation of melamine cyanurate. The present invention suppresses the (110) and (200) crystal planes by adding a crystal plane inducing agent, induces the growth of the (220) crystal plane, and the unsaturated metal center on the surface of the crystal plane inducing agent can coordinate with cyanuric acid, interferes with the formation of the MCA large plane hydrogen bond network, and limits the unlimited expansion of the hydrogen bond network, thereby achieving the effect of reducing the viscosity of the system. At the same time, the MCA synthesized by the present invention also has the characteristics of good dispersibility, high thermal stability, excellent flame retardant performance, and can significantly improve the compatibility of MCA with PA6.

[0006] The present invention provides a synthesis method for regulating the crystal plane orientation of melamine cyanurate. Furthermore, the present invention adds a crystal plane inducing agent during the synthesis process of the crystal plane orientation of melamine cyanurate, and the crystal plane inducing agent is a zeolite imidazolate skeleton material. The present invention significantly reduces the viscosity of the reaction system by adding the crystal plane inducing agent zeolite imidazolate skeleton material. Figure 1 The regulation mechanism of the crystal face inducer: during the compounding process of melamine (ME) and cyanuric acid (CA), the unsaturated metal sites on the surface of the crystal face inducer can coordinate with cyanuric acid and penetrate into the MCA prepolymer, inhibiting the mutational compounding of a large number of prepolymers, reducing the fluid dynamic radius of MCA, and reducing the viscosity of the reaction system.

[0007] Preferably, the zeolite imidazolate framework material is at least one of ZIF-8, ZIF-67, ZIF-68, ZIF-11, ZIF-70, and ZIF-90.

[0008] Preferably, the average particle size of the crystal plane inducing agent is 50 nm to 2 μm.

[0009] Preferably, the synthesis method for regulating the crystal plane orientation of melamine cyanurate comprises the following steps:

[0010] (1) mixing melamine, a dispersant, a solvent and a pH adjuster to obtain a dispersion;

[0011] (2) continuing to stir the dispersion described in step (1) at a temperature of 70° C. to 90° C. to obtain a highly dispersed melamine precursor solution;

[0012] (3) adding cyanuric acid to the highly dispersed melamine precursor solution described in step (2), maintaining the reaction temperature, stirring and mixing, adding a crystal surface inducing agent, and stirring at a constant temperature of 85° C. to 110° C. for 2 h to 6 h to obtain a white paste;

[0013] (4) The white paste in step (3) is filtered, washed, dried and crushed in sequence to obtain melamine cyanurate.

[0014] Preferably, the dispersant in step (1) is selected from at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide and dodecyltrimethylammonium chloride, and the added amount of the dispersant is 0.1wt% to 2wt% of the mass of the melamine.

[0015] Preferably, the pH of the dispersion in step (1) is 7.5 to 9.5, the stirring speed is 300 r / min to 500 r / min, and the stirring time is 1 h to 4 h.

[0016] Preferably, the solvent in step (1) is selected from at least one of water, ethanol and methanol.

[0017] Preferably, the pH regulator in step (1) is selected from at least one of ammonia water, sodium hydroxide, potassium hydroxide and triethylamine.

[0018] Preferably, the amount of the crystal plane inducing agent added in step (2) is 2 wt% to 10 wt% of the mass of melamine.

[0019] Preferably, the crystal plane orientation of the MCA synthesized in the present invention is to suppress the (110) and (200) crystal planes and induce the growth of the (220) crystal plane.

[0020] Preferably, the MCA with a specific crystal plane orientation synthesized in the present invention can be used as a flame retardant for polymers, or used in combination with other flame retardants.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention inhibits and induces specific crystal faces of MCA by adding a crystal face inducing agent, and at the same time, the unsaturated metal center on the surface of the crystal face inducing agent can coordinate with cyanuric acid, interfere with the formation of a large planar hydrogen bond network of MCA, and limit the unlimited expansion of the hydrogen bond network, thereby achieving the effect of reducing the viscosity of the system. The MCA synthesized by the present invention has good dispersibility, high thermal stability, and excellent flame retardant properties, and can significantly improve the compatibility of MCA with polymers. The present invention has great development potential in the field of polymer flame retardancy.

[0023] (2) The synthetic method for regulating the crystal plane orientation of melamine cyanurate provided by the present invention is simple in process, easy to implement, low in cost, and has mild reaction conditions. It is expected to be applied on a large scale. More importantly, it can open up new ideas for the synthesis of MCA from the perspective of crystal plane regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram of the mechanism of regulating the crystal surface of melamine cyanurate of the present invention;

[0025] Figure 2is the XRD pattern of melamine cyanurate of the present invention;

[0026] Figure 3 is a FESEM image of melamine cyanurate of the present invention, wherein: Figure 3 A in is MCA, Figure 3 B in the figure is the crystal face inducing agent ZIF-67-MCA. Figure 3 C in the figure is the crystal face inducing agent ZIF-8-MCA. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0028] The experimental methods or test methods described in the following examples are conventional methods unless otherwise specified; the raw materials and auxiliary agents are obtained from conventional commercial channels or prepared by conventional methods unless otherwise specified.

[0029] Example 1

[0030] A synthetic method for regulating the crystal plane orientation of melamine cyanurate comprises the following steps:

[0031] (1) adding 100 g of melamine (ME) and 0.1 g of sodium dodecyl sulfate into a reaction kettle, adding 2000 mL of an ethanol-water mixed solvent and a pH adjuster, potassium hydroxide, to obtain a dispersion, wherein the pH of the dispersion is 7.5;

[0032] (2) stirring the dispersion in step (1) at 70° C. and 300 r / min for 1 h to obtain a highly dispersed melamine precursor solution;

[0033] (3) adding 163 g of cyanuric acid (CA) to the highly dispersed melamine precursor solution described in step (2), maintaining the reaction temperature, stirring and mixing, adding 2 g of a crystal face inducing agent ZIF-8, whose average particle size is 50 nm, and stirring and reacting at a constant temperature of 85° C. for 6 h to obtain a white paste;

[0034] The white paste in step (3) is filtered, washed, dried and crushed in sequence to obtain melamine cyanurate.

[0035] Example 2

[0036] A synthetic method for regulating the crystal plane orientation of melamine cyanurate comprises the following steps:

[0037] (1) adding 100 g of melamine (ME) and 0.1 g of sodium dodecyl sulfate into a reaction kettle, adding 2000 mL of an ethanol-water mixed solvent and a pH adjuster, potassium hydroxide, to obtain a dispersion, wherein the pH of the dispersion is 7.5;

[0038] (2) stirring the dispersion in step (1) at 70° C. and 300 r / min for 1 h to obtain a highly dispersed melamine precursor solution;

[0039] (3) adding 163 g of cyanuric acid (CA) to the highly dispersed melamine precursor solution described in step (2), maintaining the reaction temperature, stirring and mixing, adding 2 g of a crystal face inducing agent ZIF-67, the average particle size of which is 100 nm, and stirring the reaction at a constant temperature of 85° C. for 6 h to obtain a white paste;

[0040] The white paste in step (3) is filtered, washed, dried and crushed in sequence to obtain melamine cyanurate.

[0041] Example 3

[0042] A synthetic method for regulating the crystal plane orientation of melamine cyanurate comprises the following steps:

[0043] (1) adding 100 g of melamine (ME) and 1 g of sodium dodecyl sulfate into a reaction kettle, adding 2000 mL of an ethanol-water mixed solvent and a pH adjuster, potassium hydroxide, to obtain a dispersion, wherein the pH of the dispersion is 8.5;

[0044] (2) stirring the dispersion in step (1) at 80° C. and 400 r / min for 2 h to obtain a highly dispersed melamine precursor solution;

[0045] (3) adding 163 g of cyanuric acid (CA) to the highly dispersed melamine precursor solution described in step (2), maintaining the reaction temperature, stirring and mixing, adding 4 g of a crystal face inducing agent ZIF-68, the average particle size of which is 500 nm, and stirring the reaction at a constant temperature of 95° C. for 4 h to obtain a white paste;

[0046] The white paste in step (3) is filtered, washed, dried and crushed in sequence to obtain melamine cyanurate.

[0047] Example 4

[0048] A synthetic method for regulating the crystal plane orientation of melamine cyanurate comprises the following steps:

[0049] (1) adding 100 g of melamine (ME) and 1 g of sodium dodecyl sulfate into a reaction kettle, adding 2000 mL of an ethanol-water mixed solvent and a pH adjuster, potassium hydroxide, to obtain a dispersion, wherein the pH of the dispersion is 8.5;

[0050] (2) stirring the dispersion in step (1) at 80° C. and 400 r / min for 2 h to obtain a highly dispersed melamine precursor solution;

[0051] (3) adding 163 g of cyanuric acid (CA) to the highly dispersed melamine precursor solution described in step (2), maintaining the reaction temperature, stirring and mixing, adding 4 g of a crystal face inducing agent ZIF-11, whose average particle size is 500 nm, and stirring and reacting at a constant temperature of 95° C. for 4 h to obtain a white paste;

[0052] The white paste in step (3) is filtered, washed, dried and crushed in sequence to obtain melamine cyanurate.

[0053] Example 5

[0054] A synthetic method for regulating the crystal plane orientation of melamine cyanurate comprises the following steps:

[0055] (1) adding 100 g of melamine (ME) and 2 g of sodium dodecyl sulfate into a reaction kettle, adding 2000 mL of an ethanol-water mixed solvent and a pH adjuster, potassium hydroxide, to obtain a dispersion, wherein the pH of the dispersion is 9.5;

[0056] (2) stirring the dispersion in step (1) at 90° C. and 500 r / min for 3 h to obtain a highly dispersed melamine precursor solution;

[0057] (3) adding 163 g of cyanuric acid (CA) to the highly dispersed melamine precursor solution described in step (2), maintaining the reaction temperature, stirring and mixing, adding 8 g of a crystal surface inducing agent ZIF-70, whose average particle size is 1 μm, and stirring and reacting at a constant temperature of 110° C. for 2 h to obtain a white paste;

[0058] The white paste in step (3) is filtered, washed, dried and crushed in sequence to obtain melamine cyanurate.

[0059] Example 6

[0060] A synthetic method for regulating the crystal plane orientation of melamine cyanurate comprises the following steps:

[0061] (1) adding 100 g of melamine (ME) and 2 g of sodium dodecyl sulfate into a reaction kettle, adding 2000 mL of an ethanol-water mixed solvent and a pH adjuster, potassium hydroxide, to obtain a dispersion, wherein the pH of the dispersion is 9.5;

[0062] (2) stirring the dispersion in step (1) at 90° C. and 500 r / min for 4 h to obtain a highly dispersed melamine precursor solution;

[0063] (3) adding 163 g of cyanuric acid (CA) to the highly dispersed melamine precursor solution described in step (2), maintaining the reaction temperature, stirring and mixing, adding 10 g of a crystal surface inducing agent ZIF-90 having an average particle size of 2 μm, and stirring and reacting at a constant temperature of 110° C. for 2 h to obtain a white paste;

[0064] The white paste in step (3) is filtered, washed, dried and crushed in sequence to obtain melamine cyanurate.

[0065] Comparative Example 1 is commercially available MCA purchased from Sichuan Institute of Fine Chemicals.

[0066] In Comparative Example 2, MCA was prepared in the same manner as in Example 1, but without adding a crystal face inducing agent during the preparation process.

[0067] Characterization of MCA: X-ray powder diffractometer (XRD) and field emission scanning electron microscope (FESEM) were used to characterize the crystal plane orientation and morphology changes of MCA in the present invention.

[0068] (1) XRD results show: Figure 2 As shown, by adding different crystal plane inducing agents during the MCA synthesis process, the (110) and (200) crystal planes were suppressed and the (220) crystal plane growth was induced.

[0069] (2) FESEM results show: Figure 3 As shown in the figure, the addition of crystal plane inducing agent changes the morphology of MCA.

[0070] Performance test, the specific method is as follows: add the MCA synthesized in Examples 1 to 6 of the present invention and the MCA purchased in Comparative Example 1 to PA6 (nylon 6) at an addition ratio of 8%, and obtain standard test specimens through twin-screw melting, extrusion, granulation, and injection molding. The obtained standard test specimens are tested for flame retardancy and mechanical properties. The limiting oxygen index (LOI), i.e., the decomposition temperature, is determined using the GB / T2406-93 test, and the sample size is 120×3.2×6.5mm; the vertical combustion is tested according to the UL94 standard, and the sample size is 127×12.7×3.2mm 3; The tensile strength test is carried out in accordance with GB / T1040-92, and the sample size is 80×10×4mm 3 ; The bending strength test is carried out according to GB / T9341-2000, and the sample size is 80×10×4mm 3 The test results are shown in Table 1:

[0071] Table 1 Flame retardant and mechanical properties test of products

[0072]

[0073]

[0074] As can be seen from Table 1, the mechanical properties and UL94 grades of Examples 1 to 6 of the present invention are better than the commercially available product provided in Comparative Example 1, indicating that the MCA synthesized by crystal face regulation of the present invention has the characteristics of good compatibility with polymers, high thermal stability, and excellent flame retardancy.

[0075] The MCA synthesized in Examples 1 to 6 of the present invention and Comparative Example 2 was tested for viscosity of the reaction system using an NDJ rotational viscometer. The results are shown in Table 2:

[0076] Table 2 Product reaction system viscosity test

[0077] project Crystalline surface inducing agent Reaction system viscosity (MPa·s) Example 1 ZIF-8 <![CDATA[4.0×10 5 ]]> Example 2 ZIF-67 <![CDATA[4.3×10 5 ]]> Example 3 ZIF-68 <![CDATA[4.5×10 5 ]]> Example 4 ZIF-11 <![CDATA[4.3×10 5 ]]> Example 4 ZIF-70 <![CDATA[5.0×10 5 ]]> Example 6 ZIF-90 <![CDATA[5.0×10 5 <!-- 5 -->]]> Comparative Example 2 No Addition <![CDATA[10×10 5 ]]>

[0078] As can be seen from Table 2, the viscosity of the reaction systems of Examples 1 to 6 of the present invention is lower than that of Comparative Example 2, indicating that the viscosity of the reaction system is significantly reduced by adding a crystal plane inducing agent.

[0079] In summary, the present invention regulates the crystal plane orientation of MCA by adding a crystal plane inducing agent, interferes with the formation of a large planar hydrogen bond network of MCA, reduces the viscosity of the reaction system, and the synthesized product has the characteristics of good dispersibility, high thermal stability, excellent flame retardancy, and can significantly improve the compatibility of MCA with polymers. At the same time, the synthesis method provided by the present invention has the characteristics of simple process, easy implementation, low cost, mild reaction conditions, and is expected to be applied on a large scale.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for synthesizing melamine cyanurate to adjust the crystal orientation, characterized in that: The following steps are involved: (1) mixing melamine, a dispersant, a solvent and a pH adjuster to obtain a dispersion; (2) continuing to stir the dispersion described in step (1) at a temperature of 70° C. to 90° C. to obtain a highly dispersed melamine precursor solution; (3) adding cyanuric acid to the highly dispersed melamine precursor solution described in step (2), maintaining the reaction temperature, stirring and mixing, adding a crystal surface inducing agent, and stirring at a constant temperature of 85° C. to 110° C. for 2 h to 6 h to obtain a white paste; (4) filtering, washing, drying and crushing the white paste in step (3) in sequence to obtain melamine cyanurate; The crystal face inducing agent is a zeolite imidazolate framework material; The zeolite imidazolate framework material is at least one of ZIF-8, ZIF-67, ZIF-68, ZIF-11, ZIF-70, and ZIF-90; The pH of the dispersion is 7.5 to 9.5; The amount of the crystal face inducing agent added in step (2) is 2wt% to 10wt% of the mass of melamine.

2. The method for synthesizing melamine cyanurate by controlling the crystal orientation according to claim 1, characterized in that: The average particle size of the crystal plane inducing agent is 50nm-2μm.

3. The method for synthesizing melamine cyanurate according to claim 1, characterized in that: The dispersant in step (1) is selected from at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide and dodecyltrimethylammonium chloride, and the added amount of the dispersant is 0.1wt% to 2wt% of the mass of the melamine.

4. The method for synthesizing melamine cyanurate for adjusting the crystal orientation according to claim 1, characterized in that: The stirring speed in step (1) is 300 r / min to 500 r / min, and the stirring time is 1 h to 4 h.

5. The method for synthesizing melamine cyanurate by controlling the crystal orientation according to claim 1, characterized in that: The solvent in step (1) is selected from at least one of water, ethanol and methanol.

6. The method for synthesizing melamine cyanurate for adjusting the crystal orientation according to claim 1, characterized in that: The pH regulator in step (1) is selected from at least one of ammonia water, sodium hydroxide, potassium hydroxide and triethylamine.

7. A synthetic method for regulating the crystal orientation of melamine cyanurate according to any one of claims 1 to 6, characterized in that: The melamine cyanurate synthesized by the method is used as a flame retardant for polymers, or is used in combination with other flame retardants.

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