A macromolecular phosphorus-nitrogen flame retardant composite material, its preparation method and application

Abstract

The present invention provides a macromolecular phosphorus-nitrogen flame retardant composite material, its preparation method and application, belonging to the technical field of flame retardants. By introducing a metal catalyst, a multi-functional cross-linking agent and a synergist into the piperazine pyrophosphate and melamine phosphate system, the present invention synthesizes a new type of weather-resistant intumescent flame retardant. The present invention provides a new method and a new formulation for the intumescent flame retardant system, improves the flame retardant effect of the phosphorus-nitrogen intumescent flame retardant in polypropylene materials, improves the dispersibility and water resistance of the flame retardant in the substrate, reduces the addition amount of the flame retardant, and also improves the migration resistance of the white powdery phosphorus-nitrogen intumescent flame retardant in dark polypropylene materials. The present invention has important application prospects in the field of flame retardant materials and may promote the development and innovation of the industry.

Description

Technical Field

[0001] The present invention relates to the technical field of flame retardants, and particularly to a macromolecular phosphorus-nitrogen flame retardant composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Polypropylene material is a polymer formed by the addition polymerization of propylene. It is a white waxy material with a semi-transparent appearance, and has the advantages of low density, low cost, good comprehensive performance, etc. It is widely used in technical fields such as household appliances, plastic pipes, construction, and automobiles. However, due to the melting point of polypropylene being 189 °C and the heat distortion temperature being 105 °C, its rigidity is relatively poor and the dimensional shrinkage rate is large. Moreover, the limiting oxygen index of polypropylene material is relatively low (17.4 - 18.5), the combustion speed is fast, the calorific value is large, and there is a phenomenon of molten dripping, which is very easy to cause a fire. In order to improve its safety and practicality, in addition to meeting its relevant mechanical properties, flame retardant modification is also required.

[0003] In the field of flame retardancy of polypropylene materials, intumescent flame retardancy is the most important one. Halogen-free intumescent flame retardants (IFRs) have excellent properties such as low smoke, non-toxic, halogen-free, and the formation of a carbon layer can effectively prevent polymer molten dripping, meeting the current industry requirements of smoke suppression, low toxicity, and high efficiency in the flame retardant field. Piperazine pyrophosphate is an intumescent flame retardant integrating acid source, carbon source, and gas source, with characteristics such as high charring efficiency, good thermal stability, and low hygroscopicity. However, due to the characteristics of piperazine pyrophosphate having a low pH, high water solubility, and easy moisture absorption, it causes problems such as corrosion of the screw, easy precipitation, and easy caking during storage. The melt index of piperazine pyrophosphate and polypropylene material is low during the extrusion sheet process, which will cause poor dispersion during the extrusion sheet process, and quality defects such as pitting, white spots, and unstable flame retardant performance will appear on the sheet. At present, a large number of experiments have been carried out to improve the application of piperazine pyrophosphate in PP materials through means such as compounding and modification. However, after being compounded with melamine phosphate, although the addition amount of the flame retardant is reduced and the flame retardant performance is improved, due to simple physical mixing, the problems of high water solubility and easy migration of the product always exist, resulting in limitations in the use of the compound product of piperazine pyrophosphate and melamine phosphate in PP materials, especially the problem of easy migration is particularly prominent in dark-colored substrates. Summary of the Invention

[0004] The purpose of the present invention is to provide a macromolecular phosphorus-nitrogen flame retardant composite material, a preparation method thereof, and an application thereof. By introducing a multi-functional cross-linking agent, a metal catalyst, and a synergist into the compound system of piperazine pyrophosphate and melamine phosphate, the flame retardant performance and weather resistance of the compound flame retardant are effectively improved, and then a PP material with high flame retardant performance and high weather resistance is synthesized.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a polymer, which comprises a structure shown in Formula 1 below: Formula 1

[0007] Wherein, n is an integer between 1 and 3.

[0008] The present invention also provides an application of the above polymer as a flame retardant or in the preparation of a flame retardant.

[0009] The present invention also provides a method for preparing a macromolecular phosphorus-nitrogen flame retardant composite material, comprising the following steps:

[0010] S1. Mix piperazine pyrophosphate, melamine phosphate and a metal catalyst, and obtain Polymer 1 through a polymerization reaction;

[0011] S2. Mix Polymer 1, a synergist and a polyfunctional crosslinking agent, and react to obtain a macromolecular phosphorus-nitrogen flame retardant composite material.

[0012] Preferably, the mass ratio of piperazine pyrophosphate to melamine phosphate is 1-3:1.

[0013] Preferably, in S1, the time of the polymerization reaction is 1.5-2.5 h;

[0014] The temperature of the polymerization reaction is 220-260 °C;

[0015] In S2, the mass ratio of the synergist to the crosslinking agent is 3:1.5-2.5;

[0016] The total addition amount of the synergist and the crosslinking agent is 3-8 wt%.

[0017] Preferably, the metal catalyst is selected from one or more of ferric chloride, copper chloride, cobalt chloride, nickel chloride, zinc chloride, magnesium oxide or aluminum oxide.

[0018] Preferably, the synergist is selected from one or more of PER, ALP, ODOPB, BDP, melem or melam.

[0019] Preferably, the polyfunctional crosslinking agent is selected from one or more of dioctylphosphate acyloxy titanate, 4-amino-1-butanol, 1,3,5-tris(trimethoxysilylpropyl) isocyanurate, N,N-methylenebisacrylamide, bis(2-hydroxyethyl)amino(tris(hydroxymethyl))methane or N-(β-aminoethyl)-γ-aminopropyltriethoxysilane.

[0020] The present invention also provides a macromolecular phosphorus-nitrogen flame retardant composite material prepared by the above synthesis method.

[0021] The present invention also provides a flame retardant material, comprising a plastic substrate and a flame retardant; the flame retardant contains the above polymer or the above macromolecular phosphorus-nitrogen flame retardant composite material.

[0022] Advantages of the present invention:

[0023] In the present invention, a metal catalyst, a multi-functional cross-linking agent and a synergist are introduced into the piperazine pyrophosphate and melamine phosphate system. The metal catalyst plays a certain catalytic and promoting role, and the cross-linking agent plays a bridging role in the compounding system. The cross-linking agent contains a large number of multi-functional functional groups, which not only increase the molecular weight but also increase the dispersibility of macromolecules, making the macromolecular flame retardant itself have a certain self-lubricating effect. The main function of the synergist is to improve the anti-dripping property, smoke suppression property and char-forming property. Through the combined action of the metal catalyst, the multi-functional cross-linking agent and the synergist, a new type of weather-resistant intumescent flame retardant is synthesized, and then a composite material with high weather resistance and high flame retardant performance is synthesized with a polypropylene material. The present invention provides a new method and new formula for the intumescent flame retardant system, improves the flame retardant effect of the phosphorus-nitrogen intumescent flame retardant in the polypropylene material while maintaining a small change in the mechanical properties of the substrate itself, improves the dispersibility and water resistance of the flame retardant in the substrate, reduces the addition amount of the flame retardant, and also improves the migration resistance of the white powdery phosphorus-nitrogen intumescent flame retardant in the dark polypropylene material. The present invention has an important application prospect in the field of flame retardant materials and may promote the development and innovation of the industry. Description of the drawings

[0024] Figure 1 It is a synthesis route diagram of the modified piperazine pyrophosphate / melamine phosphate polymer;

[0025] Figure 2 It is an infrared spectrum diagram of the modified piperazine pyrophosphate / melamine phosphate composite;

[0026] Figure 3 It is a thermogravimetric analysis diagram of the modified piperazine pyrophosphate / melamine phosphate composite;

[0027] Figure 4 It is a weather resistance result diagram before the modification of the piperazine pyrophosphate / melamine phosphate composite;

[0028] Figure 5 It is a weather resistance result diagram after the modification of the piperazine pyrophosphate / melamine phosphate composite. Detailed implementation manners

[0029] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0030] Embodiments

[0031] 1. Synthesis of Modified Piperazine Pyrophosphate / Melamine Phosphate Polymer

[0032] By adding a metal catalyst, a crosslinking agent and a synergist, a composite nitrogen-phosphorus intumescent flame retardant was prepared, and the synthesis route is as Figure 1 shown, where n = 1 - 3, PPAP:MP = (1 - 3):1, the unmodified polymer is abbreviated as MPA, and the modified polymer is abbreviated as MPA-HWR.

[0033] The specific steps are as follows:

[0034] In a 10 L kneader, piperazine pyrophosphate and melamine phosphate were added at room temperature, where the mass ratio of piperazine pyrophosphate to melamine phosphate was 2:1, and the metal catalyst was 5 wt%. Under a nitrogen atmosphere, the temperature of the system was raised to 240 °C, and the reaction was stirred for 2 hours to end the reaction. After cooling to room temperature, the polymer MPA was obtained. The obtained polymer MPA was added to a stirring kettle at room temperature, and a synergist and a polyfunctional crosslinking agent were added in sequence and stirred at room temperature for 2 hours to obtain a white solid powder product MPA-HWR with a yield of 95% - 98%. The mass ratio of the synergist to the crosslinking agent was 3:2, and the total addition amount was 5 wt%.

[0035] The metal catalyst is selected from ferric chloride;

[0036] The synergist is selected from PER;

[0037] The polyfunctional crosslinking agent is selected from dioctylphosphate acyloxy titanate.

[0038] 2. Fourier Transform Infrared Spectroscopy (FT-IR) Analysis

[0039] The product structure was characterized by Fourier transform infrared spectroscopy, as Figure 2 shown. Figure 2 The antisymmetric stretching vibration doublets of -NH 2 and N-H in appear at 3464 cm -1 and 3391 cm -1 ; The stretching vibration peak and bending vibration peak of NH 3 + appear at 3121 cm -1 and 1518 cm -1 respectively; The absorption peak of C-C appears at 1266 cm -1 ; The stretching vibration peak of P=O appears at 1138 cm -1 , the stretching vibration peak of P-O appears at 1167 cm -1 and 1067 cm -1 respectively, and the stretching vibration peak of P-OH appears at 974 cm -1At [location], the stretching vibration peak of P-O-P appears at 882 cm -1 At [location], the characteristic peak of the triazine ring is 1673 cm -1 At [location], the stretching vibration peak of C=N is 1455 cm -1 At [location], the stretching vibration peak of C-N is 779 cm -1 At [location], the bending vibration peak of the triazine ring.

[0040] 3. Thermogravimetric Analysis

[0041] To meet the processing requirements of plastics, the flame retardant must have good thermal stability. The thermal stability of the modified composite was evaluated by thermogravimetric analysis, as shown in Figure 3 . From Figure 3 , it can be seen that the decomposition temperature is 270 °C. The temperatures at which the modified composite loses 1.0%, 2.0%, and 5.0% of its weight are 274 °C, 278 °C, and 289 °C respectively. When the composite loses 10% of its weight, the temperature exceeds 300 °C. This indicates that the composite flame retardant has good thermal stability.

[0042] 4. Comparative diagram of the migration resistance of the modified composite flame retardant in black polypropylene material, see Figures 4 - 5 :

[0043] The modified and unmodified composite flame retardants were respectively added to the black polypropylene material, and the weather resistance of the two plates was compared in a double 85 environment. White spots appeared on the surface of sample a, while no white spots were precipitated on sample b, indicating that the unmodified flame retardant composite precipitated in the polypropylene material, and the modified compound flame retardant was more stable in the polypropylene material.

[0044] 5. Preparation of Modified Piperazine Pyrophosphate / Melamine Phosphate Polymer / Polypropylene

[0045] The dried PP (100 °C, 12 h), modified composite flame retardant, lubricant, and antioxidant were mixed in a certain proportion. Among them, the lubricant antioxidant is 0.5 wt% - 1.5 wt%, and the flame retardant is 10 wt% - 25 wt%. Under certain process parameters, it was extruded by a twin-screw extruder, cut into pellets by a pelletizer, and finally injection-molded by an injection molding machine to obtain standard specimens for mechanical and combustion performance tests. According to the GB / T 1040-2018 standard, the tensile strength and flexural strength of the PP composite were tested. The tensile speed was 10 mm / min, and the specimen size was 160×10×4 mm 3 , the flexural speed was 10 mm / min, and the specimen size was 80×10×4 mm 3 . The impact test was carried out according to the standard GB / T 1843-1996, and the specimen size was 80×10×4 mm 3(V-notch). The limiting oxygen index test was carried out according to the GB / T 2406.2-2009 standard, and the sample size was 10×10×4 mm 3 ; Vertical burning test: According to the UL-94 standard, the sample size was 125×13×5 mm 3 .

[0046] Table 1 Flame retardancy test data of PP and its composites

[0047] Performance test sample UL-94 LOI / % PP Combustion 17.50 PP / 10% MPA-HWR Combustion 23.22 PP / 15% MPA-HWR V-1 26.07 PP / 20% MPA-HWR V-0 31.21 PP / 25% MPA-HWR V-0 31.40

[0048] As can be seen from Table 1, when no flame retardant was added, the LOI value of the PP material was 17.50, which was a flammable material. When the addition amount of the MPA-HWR flame retardant was 10 wt%, the LOI value increased to 23.22. With the increase of the MPA-HWR flame retardant, the LOI value also increased. When the addition amount of the MPA-HWR flame retardant was 20 wt%, UL-94 reached the V-0 level and the LOI value was 31.21, which had reached the flame-retardant level. When the flame retardant was increased by 25 wt%, the combustion grade remained unchanged and the increase amplitude of the LOI value was small. The above data indicate that the MPA-HWR flame retardant has high flame retardancy.

[0049] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a macromolecular phosphorus-nitrogen flame retardant composite material, characterized in that: The following steps are involved: S1, mixing piperazine pyrophosphate, melamine phosphate and a metal catalyst to obtain a polymer 1 through a polymerization reaction; S2, mixing polymer 1, a synergist and a multifunctional cross-linking agent, and reacting to obtain a macromolecular phosphorus-nitrogen flame retardant composite material; The mass ratio of the piperazine pyrophosphate to the melamine phosphate is 1-3:1; In S1, the polymerization reaction time is 1.5 to 2.5 hours; The polymerization reaction temperature is 220-260°C; In S2, the mass ratio of the synergist to the multifunctional cross-linking agent is 3:1.5-2.5; The total addition amount of the synergist and the multifunctional cross-linking agent is 3-8wt%; The metal catalyst is selected from one or more of ferric chloride, cupric chloride, cobalt chloride, nickel chloride, zinc chloride, magnesium oxide or aluminum oxide; The synergist is selected from one or more of PER, ALP, ODOPB, BDP, melam or melamine; The multifunctional crosslinking agent is selected from one or more of dioctylphosphoacyloxy titanate, 4-amino-1-butanol, 1,3,5-tris(trimethoxysilylpropyl)isocyanurate, N,N-methylenebisacrylamide, bis(2-hydroxyethyl)amino(trihydroxymethyl)methane or N-(β-aminoethyl)-γ-aminopropyltriethoxysilane.

2. The macromolecular phosphorus-nitrogen flame retardant composite material prepared by the preparation method according to claim 1.

3. A flame retardant material, characterized in that: Includes plastic substrates and flame retardants; The flame retardant contains the macromolecular phosphorus-nitrogen flame retardant composite material according to claim 2.

Images