Halogen-free flame-retardant composition and method of making

Abstract

This invention provides a halogen-free flame retardant composition and its preparation method. The raw materials of the halogen-free flame retardant composition, by weight percentage, include 50%–70% polypropylene, 5%–10% reinforcing material, 20%–35% halogen-free flame retardant, 0%–10% flame retardant synergist, 0%–10% compatibilizer, 0.2%–1% anti-dripping agent, and 0.5%–2% processing aid. The halogen-free flame retardant, by weight percentage, comprises: 50%–60% metal ion-modified piperazine polyphosphate, 10%–20% metal ion-modified melamine polyphosphate containing melamine condensate, 10%–30% metal ion-modified melamine polyphosphate containing silane structure, and 2%–10% melamine cyanurate.

Description

Technical Field

[0001] This invention relates to the field of flame retardant technology, and more specifically to a halogen-free flame retardant composition and its preparation method. Background Technology

[0002] The flame retardant properties of polymer materials are directly related to public safety. In the construction, transportation, and electronics industries, the requirements for flame retardancy of materials are becoming increasingly stringent. Due to the depletion of antimony resources and environmental protection policies, the application of bromine-antimony flame retardant systems is gradually being limited, and halogen-free flame retardant technology has become an important development trend in the flame retardant field. Among these, halogen-free flame retardant technology is relatively mature in the application of polypropylene materials. Flame-retardant polypropylene is widely used in many fields such as automotive parts, electronics, construction, chemicals, and medical applications. It can be processed into electrical housings (such as electric irons and hair dryers), switches, sockets, LED lamps, power strips, as well as flame-retardant pipes, sheets, and decorative materials, providing reliable electrical insulation and flame retardant protection for various products. The highest flame retardant rating can reach the UL94 V-0 standard.

[0003] Currently, flame retardant systems for polypropylene materials are mainly divided into two categories: halogenated flame retardant systems and halogen-free flame retardant systems. Halogenated flame retardants have drawbacks such as poor high-temperature stability and low tracking index, and they produce dense smoke and harmful substances such as hydrogen bromide during combustion. Therefore, the development of safe and environmentally friendly halogen-free flame retardants has become an industry consensus.

[0004] Currently, the most widely used halogen-free flame retardant for polypropylene on the market is the halogen-free phosphorus-nitrogen intumescent flame retardant. There are two main types of this type of flame retardant technology that have achieved industrial application: one is the ammonium polyphosphate halogen-free intumescent flame retardant system. This system is based on ammonium polyphosphate and is combined with a synergistic char-forming agent to prepare halogen-free intumescent flame-retardant polypropylene. The product has high phosphorus content and excellent flame retardant efficiency, but it has problems such as low thermal stability, ammonia odor during processing, poor thermo-oxidative aging performance of the material and easy yellowing, and easy precipitation under high temperature and high humidity environments, which limits its application scenarios. The other is the pyrophosphate / piperazine polyphosphate halogen-free intumescent flame retardant system. This system is based on piperazine pyrophosphate and melamine polyphosphate. The product has good thermal stability, good weather resistance, and no precipitation. It can meet the processing requirements of halogen-free flame-retardant polypropylene and glass fiber reinforced polypropylene. Moreover, it is not easy to discolor under high temperature and high humidity environments. Its application scenarios are constantly expanding and it has gradually become the mainstream product in the market.

[0005] However, with the market's increasing demands for flame retardant performance and lightweighting of materials, the need for flame retardant properties in thin-walled polypropylene products is becoming increasingly urgent. Existing halogen-free phosphorus-nitrogen intumescent flame retardants are no longer sufficient to meet these demands—neither of the two halogen-free intumescent flame retardant systems mentioned above can achieve UL94 V-0 flame retardant certification for polypropylene materials with a thickness of less than 0.8 mm. The core reason is that thin-walled products are prone to dripping during flame retardant testing, failing to form a continuous, dense, and effective char layer, ultimately leading to flame retardant failure. Even significantly increasing the amount of flame retardant added (e.g., exceeding 40%) cannot solve this problem. Halogen-free flame retardancy for thin-walled polypropylene materials places higher demands on flame retardants: they must possess rapid charring capabilities and exert a strong gas-phase free radical quenching flame retardant effect in the early stages of ignition, thereby suppressing or even extinguishing the flame. Summary of the Invention

[0006] In order to overcome at least one deficiency of the prior art, the present invention provides a halogen-free flame retardant composition and its preparation method.

[0007] To achieve the above objectives, the present invention provides a halogen-free flame retardant composition, wherein the raw materials, by weight percentage, include 50%–70% polypropylene, 5%–10% reinforcing material, 20%–35% halogen-free flame retardant, 0%–10% flame retardant synergist, 0%–10% compatibilizer, 0.2%–1% anti-dripping agent, and 0.5%–2% processing aid; wherein the halogen-free flame retardant, by weight percentage, comprises: 50%–60% metal ion-modified piperazine polyphosphate, 10%–20% metal ion-modified melamine polyphosphate containing melamine condensate, 10%–30% metal ion-modified melamine polyphosphate containing silane structure, and 2%–10% melamine cyanurate.

[0008] The structural formula of silane-containing melamine polyphosphate modified by metal ions is as follows:

[0009] In this structure, the silane structure is located on the main chain, M1 Z+ Z1 represents the valence state of the metal ion; a and c represent the average degree of polymerization of polyphosphoric acid, with a and c both ranging from 1.6 to 4, and b = 1 or 2; R1 and R2 represent phenyl groups; the metal ion is one or more of zinc, magnesium, copper, aluminum, nickel, iron, and calcium.

[0010] The structural formula of metal ion-modified piperazine polyphosphate is as follows:

[0011] Wherein, n is the average degree of polymerization, n is 2~4, M2 is selected from Mg, Ca, Al, Zn, Fe, Ba, Cu; Z2 corresponds to the valence state of metal ion M2, selected from 1, 2 or 3; the molar ratio of phosphorus atoms, piperazine and metal ions in metal ion modified polyphosphate piperazine is 2~3:1:0.05~0.1.

[0012] Among them, metal ion-modified melamine polyphosphates containing melamine condensates include compounds of formula (I) and formula (II): (I); R5-A x -BA y -R5 (II);

[0013] Where, the structure of A is The structure of B is M3 is selected from divalent zinc ions, magnesium ions, copper ions, ferrous ions, or calcium ions; R3 is selected from H or R4; R4 is formed by m A groups and k B groups in any arrangement, where m and k are integers greater than or equal to 0, and 10 ≥ k + m ≥ 2; R5 is selected from any one of H, melamine, melamine, and melamine; x and y are integers greater than or equal to 0, and 10 ≥ x + y ≥ 2.

[0014] Among them, M1, M2, and M3 are all different, or any two or three of M1, M2, and M3 are the same. Preferably, M1, M2, and M3 can all be Zn.

[0015] In formula (I), the number of H atoms among the four R3 atoms is less than or equal to two; not all R5 atoms in the melamine polyphosphate containing melamine condensate modified by metal ions are H atoms.

[0016] The metal ion-modified piperazine polyphosphate, metal ion-modified melamine polyphosphate containing melamine condensate, and metal ion-modified melamine polyphosphate containing silane structure mentioned above can be found in Chinese inventions or invention applications with patent publication numbers CN115385952A, CN112898231A, and CN118359551A. For ease of description and distinction, this invention has uniformly modified some of the reference symbols in CN115385952A, CN112898231A, and CN118359551A, for example, changing the symbol M to M1, M2, M3, etc.

[0017] Optionally, the halogen-free flame retardant and flame retardant synergist are treated with a nano-organic silicon surface coupling agent, and the treatment amount is 0.2 wt.% to 5 wt.% of the weight of the halogen-free flame retardant and flame retardant synergist, preferably 0.5 wt.% to 3 wt.%.

[0018] Optionally, the nano-organosilicon surface coupling agent is a mixture of fumed silica and silane coupling agent, wherein the mass ratio of fumed silica to silane coupling agent is 1:(10~200), preferably 1:(30~120).

[0019] Optionally, the silane coupling agent is any one or a combination of vinyltrimethoxysilane, phenyltrimethoxysilane, and aminopropyltriethoxysilane.

[0020] Optionally, the flame retardant synergist is a phosphite including aluminum phosphite, zinc phosphite, calcium phosphite, zinc oxide, magnesium oxide, aluminum oxide, calcium oxide, zinc stannate, zinc borate, hydrotalcite, boehmite, calcium phosphate, calcium pyrophosphate, aluminum phosphate, magnesium phosphate, titanium phosphate, and zirconium phosphate; preferably, it is a combination of aluminum phosphite, zinc phosphite, zinc oxide, zinc stannate, zirconium phosphate, calcium phosphate, and calcium pyrophosphate.

[0021] Optionally, the reinforcing material is any one or a combination of glass fiber, glass beads, and mineral filler; Optionally, the compatibilizer is any one or a combination of several of PP-g-MAH, POE-g-MAH, and PE-g-MAH; preferably, PP is grafted with maleic anhydride.

[0022] Optionally, processing aids include lubricants and antioxidants. EBFF is preferably used as a lubricant, and 1098 and H161 are preferred antioxidants.

[0023] Optionally, the anti-dripping agent is a polytetrafluoroethylene-based anti-dripping agent.

[0024] Optionally, the amount of nano-organosilicon surface coupling agent treated is 0.5 wt.% to 3 wt.% of the weight of the halogen-free flame retardant and flame retardant synergist; the nano-organosilicon surface coupling agent is a mixture of fumed silica and silane coupling agent, and the mass ratio of fumed silica to silane coupling agent is 1:(30~120).

[0025] Optionally, the phosphorus content of the melamine polyphosphate containing melamine condensate modified by metal ions is 15 wt.%-19 wt.%; the pH% range in a 10% suspension at 25°C is 5.5-7.0; the water solubility at 20°C is ≤0.2 g / 100 ml water; and the decomposition temperature of 0.5 wt.% is ≥320°C.

[0026] The present invention also provides a method for preparing the halogen-free flame retardant composition according to any one or more of the above, comprising: Polypropylene, a mixture of halogen-free flame retardant and flame retardant synergist, compatibilizer, anti-dripping agent, and processing aid are mixed according to the specified ratio and fed into the extruder through the main feed port; reinforcing material is fed into the extruder through the side feed port; after melt blending at 170℃~210℃, the mixture is cooled, air-dried, and granulated to obtain a halogen-free flame retardant composition.

[0027] Optionally, the added halogen-free flame retardant and flame retardant synergist mixture is a treated halogen-free flame retardant and flame retardant synergist, and the steps include: after mixing the halogen-free flame retardant and flame retardant synergist evenly, adding 0.2wt.%~5wt.% of nano-organic silicone surface coupling agent of the total mass of the halogen-free flame retardant and flame retardant synergist, and mixing and dispersing evenly.

[0028] Optionally, the nano-organosilicon surface coupling agent is a mixture of fumed silica and silane coupling agent, with a mass ratio of fumed silica to silane coupling agent of 1:(10~200).

[0029] In summary, based on invention patents CN115385952A, CN112898231A, and CN118359551A, this invention improves the anti-dripping properties of materials by introducing a phosphorus-silicon structure, while simultaneously optimizing the formulation and performing metal ion synergistic modification on pyro / piperazine polyphosphate, melamine polyphosphate containing melamine condensate, and melamine polyphosphate containing silane structure, thereby improving the char formation efficiency and anti-dripping performance of the flame retardant system.

[0030] Simultaneously, by combining nano-organic silicon surface coupling materials, the compatibility between the flame retardant and the polypropylene matrix is ​​further improved, ultimately enabling the material to meet the flame retardant requirements of ultra-thin polypropylene products with a thickness of less than 0.8 mm, or even less than 0.4 mm, and to possess excellent migration resistance.

[0031] This halogen-free flame retardant combines phosphorus, nitrogen, silicon, and metal elements, exhibiting a high thermal decomposition temperature and good thermal stability. It employs a multi-layered flame retardant mechanism involving free radical capture, gas phase, and condensed phase. By capturing free radicals, isolating oxygen and heat in the condensed phase, and diluting oxygen in the gas phase, it extinguishes the flame, achieving a synergistic flame retardant effect. It exhibits excellent flame retardant properties, rapid char formation, and fast self-extinguishing. The prepared halogen-free flame-retardant polypropylene can achieve a V0 of 0.4 mm and is resistant to migration under high temperature and high humidity conditions. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] The embodiments of the present invention use the following raw materials: PP: K7926, Shanghai SECCO Metal ion modified polyphosphate piperazine: Produced by Hangzhou Jiersi Flame Retardant Chemical Co., Ltd.

[0034] Metal ion modified silane-containing melamine polyphosphate: produced by Hangzhou Jiersi Flame Retardant Chemical Co., Ltd.

[0035] Metal ion modified melamine polyphosphate containing melamine condensate: produced by Hangzhou Jiersi Flame Retardant Chemical Co., Ltd.

[0036] Aluminum phosphite: Produced by Hangzhou Jiersi Flame Retardant Chemical Co., Ltd. Compatibilizer: PP grafted with maleic anhydride, KT-1 Shenyang Ketong Other raw materials are available commercially. According to the proportions in Table 1, PP resin, antioxidant, lubricant, treated flame retardant, flame retardant synergist mixture, anti-dripping agent, and compatibilizer are added to a mixer and mixed. The mixture is then fed into the extruder through the main feed port. Glass fiber is fed into the extruder through the side feed port. After melt blending at 170℃~210℃, the mixture is cooled, air-dried, and granulated to obtain a series of thin-walled, migration-resistant, halogen-free flame-retardant polypropylenes.

[0037] After the flame retardant and flame retardant synergist are mixed evenly, 2% by mass of nano-organic silicon surface coupling agent is added to the flame retardant and flame retardant synergist. The mixture is then mixed and dispersed evenly in a high-speed mixer. The nano-organic silicon surface coupling agent is composed of fumed silica and phenyltrimethoxysilane in a mass ratio of 1:80.

[0038] The halogen-free flame-retardant polypropylene materials prepared in Comparative Examples 1-5 and Examples 1-10 were injection molded at an injection molding temperature of 200℃~220℃ to obtain test specimens. The relevant performance tests of the test specimens are detailed in Table 2 below.

[0039] The inventors also tried to replace aluminum phosphite with one or more of the following: zinc phosphate, calcium phosphite, zinc oxide, magnesium oxide, aluminum oxide, calcium oxide, zinc stannate, zinc borate, hydrotalcite, boehmite, calcium phosphate, calcium pyrophosphate, aluminum phosphate, magnesium phosphate, titanium phosphate, and zirconium phosphate, with similar results.

[0040] The inventors also tried to replace GF with one or more combinations of glass beads and mineral fillers, with similar results.

[0041] The inventors also tried using one or more of POE-g-MAH and PE-g-MAH to replace PP grafted with maleic anhydride, with similar results. The flame retardancy was slightly worse, requiring the addition of more flame retardant.

[0042] The inventors also tried to modify the product with different metal ions, as shown in Table 3. The only difference between these examples and Example 2 is the metal ions.

[0043] Comparative Example 5 did not use silane treatment, and was otherwise the same as Example 5.

[0044] Table 1. Component content of Examples 1-5 and Comparative Examples 1-5

[0045] Table 2 Test data for the embodiments and comparative embodiments

[0046] Table 3 Comparison of Examples of Modification with Different Metal Ions

[0047] The formulations of Examples 6-10 are equivalent to those of Example 5.

[0048] Table 4 Test data for Examples 6-10

[0049] As can be seen from the above examples, the metal ion modified piperazine polyphosphate, the metal ion modified melamine polyphosphate containing melamine condensate, and the flame retardant synergist are used in combination to produce products with high temperature resistance and excellent flame retardant performance. The prepared halogen-free flame retardant polypropylene material can achieve a 0.4mm V0 glow wire ignition temperature ≥750℃, and at the same time has good resistance to exudation in high temperature and high humidity environments, achieving a 1+1+1>3 effect.

[0050] Although the present invention has been disclosed above by way of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of protection claimed in the claims.

Claims

1. A halogen-free flame retardant composition, characterized in that, The raw materials, by weight percentage, include: Polypropylene 50%–70%, Reinforcing materials: 5%–10% Halogen-free flame retardant 20%–35%, Flame retardant synergist 0%–10%, Compatibilizer 0%–10%, Anti-dripping agent 0.2%–1%, Processing aids: 0.5%–2%; The halogen-free flame retardant, by weight percentage, comprises the following raw materials: Metal ion modified piperazine polyphosphate 50%–60%, Metal ion modification of 10%–20% melamine polyphosphate containing melamine condensate. 10%–30% of melamine polyphosphate containing silane structure was modified with metal ions. Melamine cyanurate 2%–10%; The structural formula of the metal ion-modified silane-containing melamine polyphosphate is as follows: In this structure, the silane structure is located on the main chain, M1 Z+ Z1 represents the valence state of the metal ion; a and c represent the average degree of polymerization of polyphosphoric acid, with a and c both ranging from 1.6 to 4, and b = 1 or 2; R1 and R2 represent phenyl groups; the metal ion is one or more of zinc, magnesium, copper, aluminum, nickel, iron, and calcium. The structural formula of the metal ion-modified piperazine polyphosphate is as follows: Wherein, n is the average degree of polymerization, n is 2~4, M2 is selected from Mg, Ca, Al, Zn, Fe, Ba, Cu; Z2 corresponds to the valence state of metal ion M2, selected from 1, 2 or 3; the molar ratio of phosphorus atoms, piperazine and metal ions in the metal ion modified polyphosphate piperazine is 2~3:1:0.05~0.1; The metal ion-modified melamine polyphosphate containing melamine condensate includes compounds of formula (I) and formula (II): （I）； R5-A x -B-A y -R5 (II); Where, the structure of A is The structure of B is M3 is selected from divalent zinc ions, magnesium ions, copper ions, ferrous ions, or calcium ions; R3 is selected from either H or R4; R4 is formed by m A groups and k B groups in any arrangement, where m and k are integers greater than or equal to 0, and 10 ≥ k + m ≥ 2; R5 is selected from any one of H, melamine, melamine, and melamine; x and y are integers greater than or equal to 0, and 10 ≥ x + y ≥ 2; Among them, M1, M2, and M3 are all different, or any two or three of M1, M2, and M3 are the same; In formula (I), the number of H atoms among the four R3 atoms is less than or equal to two; not all R5 atoms in the melamine polyphosphate containing melamine condensate modified by metal ions are H atoms.

2. The halogen-free flame retardant composition according to claim 1, characterized in that, The halogen-free flame retardant and flame retardant synergist are treated with a nano-organic silicon surface coupling agent, and the treatment amount is 0.2 wt.%~5 wt.% of the weight of the halogen-free flame retardant and flame retardant synergist.

3. The halogen-free flame retardant composition according to claim 2, characterized in that, The nano-organosilicon surface coupling agent is a mixture of fumed silica and silane coupling agent, with a mass ratio of fumed silica to silane coupling agent of 1:(10~200).

4. The halogen-free flame retardant composition according to claim 3, characterized in that, The silane coupling agent is any one or a combination of vinyltrimethoxysilane, phenyltrimethoxysilane, and aminopropyltriethoxysilane.

5. The halogen-free flame retardant composition according to claim 1, characterized in that, The flame retardant synergist is a phosphite including any one or a combination of several of the following: aluminum phosphite, zinc phosphite, calcium phosphite, zinc oxide, magnesium oxide, aluminum oxide, calcium oxide, zinc stannate, zinc borate, hydrotalcite, boehmite, calcium phosphate, calcium pyrophosphate, aluminum phosphate, magnesium phosphate, titanium phosphate, and zirconium phosphate. The reinforcing material is any one or a combination of several of glass fiber, glass beads, and mineral filler; The compatibilizer is any one or a combination of several of PP-g-MAH, POE-g-MAH, and PE-g-MAH. The processing aids include lubricants and antioxidants; The anti-dripping agent is a polytetrafluoroethylene-based anti-dripping agent.

6. The halogen-free flame retardant composition according to claim 2, characterized in that, The amount of the nano-organosilicon surface coupling agent treated is 0.5 wt.% to 3 wt.% of the weight of the halogen-free flame retardant; the nano-organosilicon surface coupling agent is a mixture of fumed silica and silane coupling agent, and the mass ratio of fumed silica to silane coupling agent is 1:(30~120).

7. The halogen-free flame retardant composition according to claim 1, characterized in that, The phosphorus content of the metal ion-modified melamine polyphosphate containing melamine condensate is 15 wt.%-19 wt.%; the pH range of a 10 wt.% suspension at 25°C is 5.5-7.0; and the water solubility at 20°C is ≤0.2g / 100ml water. The thermal decomposition temperature of 0.5 wt.% is ≥320℃.

8. A method for preparing a halogen-free flame retardant composition according to any one of claims 1 to 7, characterized in that, include: Polypropylene, a mixture of halogen-free flame retardant and flame retardant synergist, compatibilizer, anti-dripping agent, and processing aid are mixed according to the specified ratio and fed into the extruder through the main feed port; reinforcing material is fed into the extruder through the side feed port; after melt blending at 170℃~210℃, the mixture is cooled, air-dried, and granulated to obtain the halogen-free flame retardant composition.

9. The preparation method according to claim 8, characterized in that, The added halogen-free flame retardant and flame retardant synergist mixture is the treated halogen-free flame retardant and flame retardant synergist. The treatment steps include: after mixing the halogen-free flame retardant and flame retardant synergist evenly, adding 0.2wt.%~5wt.% of nano-organic silicone surface coupling agent of the total mass of the halogen-free flame retardant and flame retardant synergist, and mixing and dispersing evenly.

10. The preparation method according to claim 9, characterized in that, The nano-organosilicon surface coupling agent is a mixture of fumed silica and silane coupling agent, with a mass ratio of fumed silica to silane coupling agent of 1:(10~200).

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