Flame-retardant tpu composite material and preparation method thereof

Abstract

The application discloses a kind of flame-retardant TPU composite material and preparation method thereof, belong to the field of plastic processing.It is with melamine, phenyl boronic acid as raw material preparation melamine phenyl borate, and with magnesium-aluminum layered double hydroxide compounding, using melt blending, extrusion molding method prepares a kind of flame-retardant TPU composite material.The obtained flame-retardant TPU composite material has excellent mechanical properties, thermal stability and flame-retardant performance, it can realize surface rapidly carbonization when burning test, with strong smoke suppression effect, and can realize rapid off-fire self-extinguishing.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of plastic processing, and particularly relates to a flame-retardant TPU composite material and a preparation method thereof. BACKGROUND

[0002] Thermoplastic polyurethane elastomer (TPU) is a linear block copolymer formed by curing and granulating polyol, diisocyanate and chain extender. Its molecular structure is linear or only slightly cross-linked, and the soft segment part of the system is composed of a flexible polymer dihydric alcohol with a certain molecular weight, which gives TPU excellent high elasticity; the hard segment part of the system is composed of diisocyanate and small molecule chain extender, which provides high strength of TPU. The high molecular weight main chain is composed of soft segment and hard segment. Among the many polyurethane materials, thermoplastic polyurethane elastomer (TPU) exhibits the high elasticity of traditional rubber at room temperature, and has the plasticity of ordinary plastic at high temperature, combining the characteristics of plastic and rubber. TPU has high production efficiency, and can be processed by common processing techniques of thermoplastic plastics, such as melt blending extrusion molding, etc. for secondary processing. And thermoplastic polyurethane elastomer (TPU) can be recycled, has low production cost and is environmentally friendly, belongs to environmentally friendly polymer materials, and meets the concept of green and sustainable development. TPU has excellent properties such as high wear resistance, low temperature resistance, good ductility, high strength and biocompatibility, and is widely used in biomedical engineering, construction engineering, national defense and military industry and other industries.

[0003] However, TPU has a fatal defect in use, and its oxygen index is usually only 18-23%, and toxic gases such as HCN and CO are released during combustion, and serious melt dripping phenomenon occurs during combustion, accompanied by thick black smoke. The flammability of the material itself needs to be improved to make it more convenient to apply. The material needs to be modified by flame-retardant functionalization to make it difficult to burn. The addition of flame retardant can make the polyurethane material extinguish faster during combustion, slow down the decomposition of the material itself, greatly reduce the release of flammable gas and toxic components, and its reasonable use can reduce fire loss.

[0004] Common flame-retardant elements include halogen elements, N, P, B, Al, etc., among which commercially available flame retardants are mainly halogen-based flame retardants. However, halogen-based flame retardants will release toxic gases and a large amount of smoke when ignited by open flame at high temperature, which will cause serious pollution to the environment. The development of new high-efficiency, non-toxic and environmentally friendly flame retardants has become the direction of development in the field of flame retardants. SUMMARY

[0005] The present application aims to provide a flame-retardant TPU composite material which has good flame-retardant effect and processing performance.

[0006] To achieve the above object, the present application adopts the following technical solutions:

[0007] A flame-retardant TPU composite material, raw materials used in the preparation of the flame-retardant TPU composite material include, by weight fraction: melamine phenyl borate flame retardant 5-10 parts, magnesium aluminum layered double metal hydroxide 5-10 parts, TPU particles 85-90 parts.

[0008] The melamine phenyl borate flame retardant is prepared by the following steps:

[0009] At 95℃, 200mL of deionized water and 0.1mol of melamine are added to a 500mL three-necked flask, stirred for 10min until highly dispersed, then 0.11mol of phenyl borate is slowly added in batches, and the stirring is continued for 1.5h until the reaction is complete. After the reaction is cooled to room temperature, the filter cake is washed with deionized water and placed in a vacuum drying oven at 80℃ for 4h to obtain white melamine phosphate crystals.

[0010] The magnesium aluminum layered double metal hydroxide is prepared by the following steps:

[0011] Aluminum magnesium layered double metal hydroxide is prepared by co-precipitation method. The steps are: (1) 0.02mol of AlCl3·6H2O and 0.06mol of MgCl2·6H2O are weighed and added to 60mL of deionized water, and stirred at 30℃ until completely dissolved; (2) 0.02mol of Na2CO3 and 0.12mol of NaOH mixed solution are weighed and added to 60mL of deionized water to prepare a mixed solution; (3) slowly add the mixed solution prepared in step (2) to the solution prepared in step (1) at 60℃ under magnetic stirring until pH=13, then continue stirring for 0.5h (4) move the solution to the reaction kettle and place it in a 60℃ air drying oven for 16h; (5) the lower precipitate is centrifuged 4 times and dried to obtain magnesium aluminum layered double metal hydroxide.

[0012] The preparation of the flame-retardant TPU composite material includes the following steps:

[0013] 1) Melamine phenyl borate and magnesium aluminum layered double metal hydroxide are added to DMF, ultrasonic for 30min, then slowly add TPU particles at 85℃ and dissolve, react for 2h;

[0014] 2) After evaporating the DMF, extruding and granulating to obtain the flame-retardant TPU composite material.

[0015] Further, the temperature of each zone in the extrusion granulation is 160-200 DEG C, and the rotating speed is 400-600 r / min.

[0016] The present application has the advantages of:

[0017] (1) The melamine phenyl borate prepared by using the environment-friendly melamine and phenyl borate as raw materials, and compounded with the aluminum magnesium layered double hydroxide, the prepared TPU composite material has the benefits of health and environmental protection.

[0018] (2) The melamine phenyl borate prepared by the present application contains rich N and B elements in the structure, the N-containing part is thermally decomposed after heating to release non-combustible NH3 and N2, etc., which plays a role in diluting the concentration of oxygen and combustible gas; meanwhile, the B-containing part can be decomposed and migrated to the surface of the polymer to play a role in catalyzing carbonization and enhancing the surface carbon layer. And due to the introduction of benzene ring in the structure, the compatibility with the TPU matrix is improved, overcoming the shortcomings of the traditional nitrogen-based flame retardant, such as easy agglomeration in the matrix and poor compatibility with the matrix, and maintaining good flame retardant performance.

[0019] (3) The melamine phenyl borate prepared by the present application has nitrogen ring structure and benzene ring structure, which can be used as a flame retardant and a coupling agent when it is added to the TPU matrix and compounded with the aluminum magnesium layered double hydroxide. The special structure of the melamine phenyl borate, which is in the form of a filament with small balls at both ends, can increase the compatibility with the matrix and the inorganic filler (aluminum magnesium layered double hydroxide), and can act as a crosslinking point in the matrix, making the stress distribution uniform, thereby improving the tensile strength of the composite material. The new synergistic flame retardant system formed by the melamine phenyl borate and the aluminum magnesium layered double hydroxide can overcome the shortcomings of TPU materials, such as flammability and easy production of smoke during combustion. When the TPU composite material containing 15% of the flame retardant system burns, the polymer can form carbon on the surface rapidly without burning, and can self-extinguish rapidly after the fire source is removed, and has a strong smoke suppression effect. The flame retardant system can significantly improve the flame retardant performance of TPU while maintaining the original mechanical properties of TPU to the greatest extent.

[0020] (4) The aluminum magnesium layered double hydroxide prepared by the present application can be dispersed in the TPU matrix to play a role in heterogeneous nucleation, thereby improving the crystallization performance of the hard segment of TPU and playing a reinforcing role. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 SEM image of the aluminum magnesium layered double hydroxide prepared by the present application.

[0022] Figure 2SEM image of the melamine phenyl borate prepared in the present application.

[0023] Figure 3 FTIR image of the melamine phenyl borate prepared in the present application. DETAILED DESCRIPTION

[0024] In order to make the content of the present application more convenient to understand, the technical solutions of the present application are further described below in combination with specific embodiments, but the present application is not limited to this.

[0025] Preparation of a melamine phenyl borate flame retardant includes the following steps:

[0026] At 95℃, 200mL deionized water and 0.1mol melamine were added into a 500mL three-necked flask, and after stirring for 10min to highly disperse, 0.11mol phenyl borate was slowly added in batches, and the stirring was continued for 1.5h until the reaction was complete. After the reaction was cooled to room temperature, it was filtered, the filter cake was washed with deionized water, and then placed in a vacuum drying oven at 80℃ and baked for 4h to obtain melamine phosphate white crystals.

[0027] Preparation of a magnesium-aluminum layered double hydroxide includes the following steps:

[0028] The aluminum-magnesium layered double metal hydroxide was prepared by coprecipitation. The steps are as follows: (1) 0.02mol AlCl3·6H2O and 0.06mol MgCl2·6H2O were weighed according to the molar ratio of X=[n(Al3+) / n(Mg2+)]=1 / 3, and added to 60mL deionized water, and stirred at 30℃ until completely dissolved; (2) 0.02mol Na2CO3 and 0.12mol NaOH mixed solution were weighed and added to 60mL deionized water to prepare a mixed solution; (3) slowly add the mixed solution prepared in step (2) to the solution prepared in step (1) at 60℃ under magnetic stirring until the pH is 13, then continue to stir for 0.5h (4) move the solution to a reaction kettle and place it in a 60℃ air drying oven for 16h; (5) the lower precipitate is centrifuged 4 times and dried to obtain the magnesium-aluminum layered double metal hydroxide.

[0029] Figure 1 SEM image of the aluminum-magnesium layered double metal hydroxide prepared in the present application, which can be seen that the prepared aluminum-magnesium layered double metal hydroxide presents a stacked sheet shape. Figure 2 SEM image of the melamine phenyl borate prepared in the present application, which can be seen that the prepared melamine phenyl borate is filamentous, and the two ends are capped with small balls. Figure 3The FTIR diagram of the melamine phenyl borate prepared in the application. The deformation vibration absorption peak of NH2 is at 619, the ring stretching vibration absorption peaks are at 1654, 1550, 1467 and 1404, the symmetric and anti-symmetric stretching vibration absorption peaks of NH are at 3419 and 3135, the symmetric stretching vibration peak of B-OH is at 1350, which indicates that the melamine phenyl borate is successfully synthesized.

[0030] The structure of the melamine phenyl borate is as follows:

[0031]

[0032] Example 1

[0033] 1) 2 parts by weight of melamine phenyl borate and 3 parts by weight of magnesium-aluminum layered double hydroxide are added into DMF, and after ultrasonic treatment for 30 min, they are transferred to a rotary evaporator, heated to 85°C, 95 parts by weight of TPU particles are slowly added, and rotation is used to dissolve them, and the reaction is carried out for 2 h;

[0034] 2) After the remaining DMF in the reaction is removed by rotary evaporation, it is taken out and transferred to a twin-screw extruder, the temperature of each zone is adjusted to 160°C, the rotation speed is 400 r / min, and the flame-retardant TPU composite material is prepared by extrusion granulation.

[0035] Example 2

[0036] 1) 4 parts by weight of melamine phenyl borate and 6 parts by weight of magnesium-aluminum layered double hydroxide are added into DMF, and after ultrasonic treatment for 30 min, they are transferred to a rotary evaporator, heated to 85°C, 90 parts by weight of TPU particles are slowly added, and rotation is used to dissolve them, and the reaction is carried out for 2 h;

[0037] 2) After the remaining DMF in the reaction is removed by rotary evaporation, it is taken out and transferred to a twin-screw extruder, the temperature of each zone is adjusted to 160°C, the rotation speed is 400 r / min, and the flame-retardant TPU composite material is prepared by extrusion granulation.

[0038] Example 3

[0039] 1) 7 parts by weight of melamine phenyl borate and 8 parts by weight of magnesium-aluminum layered double hydroxide are added into DMF, and after ultrasonic treatment for 30 min, they are transferred to a rotary evaporator, heated to 85°C, 85 parts by weight of TPU particles are slowly added, and rotation is used to dissolve them, and the reaction is carried out for 2 h;

[0040] 2) After the remaining DMF in the reaction is removed by rotary evaporation, it is taken out and transferred to a twin-screw extruder, the temperature of each zone is adjusted to 160°C, the rotation speed is 400 r / min, and the flame-retardant TPU composite material is prepared by extrusion granulation.

[0041] Comparative Example 1

[0042] Pure TPU sample.

[0043] Comparative Example 2

[0044] 1) 10 parts by weight of melamine phenyl borate was added into DMF, after ultrasonic treatment for 30 min, it was transferred to a rotary evaporator, heated to 85°C, 90 parts by weight of TPU particles were slowly added, and it was dissolved by rotation, and reacted for 2h;

[0045] 2) After removing the remaining DMF in the reaction, it was taken out and transferred to a twin-screw extruder, the temperature of each zone was adjusted to 160°C, the rotation speed was 400r / min, and the flame-retardant TPU composite material was prepared by extrusion granulation.

[0046] Comparative Example 3

[0047] 1) 10 parts by weight of magnesium aluminum layered double hydroxide was added into DMF, after ultrasonic treatment for 30 min, it was transferred to a rotary evaporator, heated to 85°C, 90 parts by weight of TPU particles were slowly added, and it was dissolved by rotation, and reacted for 2h;

[0048] 2) After removing the remaining DMF in the reaction, it was taken out and transferred to a twin-screw extruder, the temperature of each zone was adjusted to 160°C, the rotation speed was 400r / min, and the flame-retardant TPU composite material was prepared by extrusion granulation.

[0049] Comparative Example 4

[0050] 1) 10 parts by weight of melamine phenyl borate was added into DMF, after ultrasonic treatment for 30 min, it was transferred to a rotary evaporator, heated to 85°C, 90 parts by weight of TPU particles were slowly added, and it was dissolved by rotation, and reacted for 2h;

[0051] 2) After removing the remaining DMF in the reaction, it was taken out and transferred to a twin-screw extruder, the temperature of each zone was adjusted to 160°C, the rotation speed was 400r / min, and the flame-retardant TPU composite material was prepared by extrusion granulation.

[0052] The samples obtained in the examples and comparative examples were tested for performance, and the results are shown in Table 1.

[0053] Table 1 Performance test results of samples

[0054]

[0055] The data in Table 1 show that when the amount of the auxiliary additive reaches 15 parts, the oxygen index of the sample can reach 29.2, and the UL-94 rating is V-0. With the increase of the amount of the auxiliary additive, the tensile strength and elongation at break of the sample also increase to a certain extent, which shows that the auxiliary additive used in the application can also effectively improve the mechanical properties of the sample. Compared with the comparative example 1 without adding the auxiliary additive, the comparative example 2 adding only 10 parts by weight of melamine phenyl borate, and the comparative example 3 adding only 10 parts by weight of magnesium-aluminum layered double hydroxide, the flame-retardant effect of the TPU composite material prepared in the example 2 is significantly improved, which shows that the prepared melamine phenyl borate can synergistically flame-retardant with the magnesium-aluminum layered double hydroxide, and has the effect of 1+1>2. In addition, the comparative example 4 adding only 10 parts by weight of melamine phosphate has a lower flame-retardant effect than the example 2 and the comparative example 2, which shows that the prepared melamine phenyl borate in the application can achieve better flame-retardant effect.

[0056] The above description is only the preferred embodiment of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be included in the scope of the present application.

Claims

1. A flame retardant TPU composite material, characterized in that: The raw materials used include, by weight fraction: melamine phenyl borate flame retardant 5-10 parts, magnesium aluminum layered double hydroxide 5-10 parts, TPU particles 85-90 parts.

2. The flame retardant TPU composite according to claim 1, characterized in that: The preparation of the melamine phenyl borate flame retardant includes the following steps: adding 200 mL of deionized water and 0.1 mol of melamine into a three-necked flask at 95°C, stirring for 10 min until highly dispersed, then slowly adding 0.11 mol of phenyl borate in batches, continuing to stir for 1.5 h until the reaction is complete, filtering the reaction product after cooling to room temperature, washing the filter cake with deionized water, and then placing it in a vacuum drying oven at 80°C for 4 h to obtain the melamine phenyl borate flame retardant.

3. The flame retardant TPU composite of claim 1, wherein: The preparation of the magnesium aluminum layered double hydroxide includes the following steps: (1) respectively weighing 0.02 mol of AlCl3·6H2O and 0.06 mol of MgCl2·6H2O, adding to 60 mL of deionized water, and stirring at 30°C under magnetic stirring until completely dissolved; (2) weighing 0.02 mol of Na2CO3 and 0.12 mol of NaOH, adding to 60 mL of deionized water, and preparing a mixed solution; (3) slowly adding the mixed solution prepared in step (2) to the solution prepared in step (1) drop by drop under magnetic stirring at 60°C until the pH is 13, then continuing to stir for 0.5 h; (4) moving the solution to a reaction kettle and placing it in a 60°C air-drying oven for crystallization for 16 h; (5) after 4 times of centrifugation and drying, the lower precipitate is obtained as the magnesium aluminum layered double hydroxide.

4. The process for preparing a flame retardant TPU composite material according to claim 1, characterized in that: including the following steps: 1) adding the melamine phenyl borate and the magnesium aluminum layered double hydroxide into DMF, ultrasonicating for 30 min, then slowly adding the TPU particles and dissolving them at 85°C, and reacting for 2 h; 2) after evaporating the DMF, extruding and granulating to obtain the flame-retardant TPU composite material.

5. A process for the preparation of a flame retardant TPU composite according to claim 4, characterized in that: The temperature of each zone in the extrusion granulation is 160-200°C, and the rotation speed is 400-600 r / min.

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