A high-concentration reinforced halogen-free flame-retardant master batch for PBT, a preparation method and application thereof

Abstract

The application discloses a high-concentration reinforced halogen-free flame-retardant master batch for PBT and a preparation method and application thereof. The master batch comprises a carrier resin and a flame retardant, the carrier resin comprises a copolymer containing a non-polar saturated carbon chain segment and a polar ester segment; the flame retardant comprises an alkyl hypophosphite; and the halogen-free flame-retardant master batch further comprises a lubricant, which is a bisamide compound formed by a saturated C12-18 acid and a diamine. The copolymer can be ethylene-methyl acrylate copolymer, and the lubricant can be ethylene bis-stearamide EBS. The master batch can be used for flame retardation of PBT, and can significantly improve the flame-retardant property of the PBT composite material under the premise of ensuring good compatibility of the PBT composite material and ensuring mechanical property of the PBT composite material, and realizes halogen-free flame retardation.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-concentration reinforced halogen-free flame-retardant masterbatch for PBT, a preparation method and application thereof. BACKGROUND

[0002] Polybutylene terephthalate, referred to as PBT, is a thermoplastic engineering plastic, which is polymerized by terephthalic acid and butanediol through condensation polymerization. The most widely used PBT material on the market is a product that is reinforced by glass fiber and modified by halogen flame retardant (usually bromine flame retardant), and is widely used in lighting lamps, cooling fans, connectors, coil skeletons, electrical enclosures and other electronic and electrical components. For example, patent CN101168618A (published on April 30, 2008) discloses a flame-retardant reinforced PBT resin with high strength and light aging resistance, which uses halogen flame retardant to achieve flame retardation. In recent years, with the increasing emphasis on environmental protection by the European Union and countries around the world, and the gradual introduction of various environmental protection regulations, especially the future Rohs regulation, which is likely to list all halides as prohibited substances, the trend of halogen-free plastic materials is irreversible, and the use of halogen-free flame retardant materials in PBT products is a development trend.

[0003] The current halogen-free flame retardant for modifying PBT mainly includes resorcinol bis(diphenyl phosphate) or hypophosphite, which is low-smoke and halogen-free, and can improve the flame retardant properties of polybutylene terephthalate. For example, patent CN102575106A discloses a flame-retardant resin composition, which comprises a thermoplastic resin and an organic phosphorus-based flame retardant. The thermoplastic resin can be selected from polyethylene terephthalate, and the organic phosphorus-based flame retardant can be a metal hypophosphite, a melamine phosphate compound, an ammonium phosphate compound, and a polyphosphazene compound. However, these halogen-free flame retardants still have some deficiencies, such as resorcinol bis(diphenyl phosphate) flame retardant, which is a liquid, inconvenient to use, has low thermal decomposition temperature, low flame retardant efficiency, and low flame retardant dripping resistance; hypophosphite flame retardant is prone to decomposition during use, which has an explosion risk and can cause a significant decrease in the mechanical properties of PBT materials.

[0004] It is difficult to significantly improve the flame retardant properties of PBT materials while ensuring their mechanical properties and achieving halogen-free environmental protection in the field of flame retardant materials. SUMMARY

[0005] In view of the shortcomings and deficiencies of the prior art, the present application provides an improved flame retardant for PBT, which can be used in PBT materials, can significantly improve the flame retardant properties of the materials while ensuring their mechanical properties, and can achieve halogen-free flame retardation.

[0006] To achieve the above-mentioned purposes, the technical solutions adopted by the present application are as follows:

[0007] A halogen-free flame-retardant masterbatch, comprising a carrier resin and a flame retardant, the carrier resin comprising a copolymer containing a non-polar saturated carbon chain segment and a polar ester segment; the flame retardant comprising an alkyl phosphinate salt; the halogen-free flame-retardant masterbatch further comprising a lubricant, the lubricant being a bisamide compound formed from a saturated C12-18 acid and a diamine.

[0008] In some embodiments, the copolymer is selected from a combination of one or more of ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-butyl methacrylate copolymer.

[0009] In some embodiments, the lubricant is ethylene bis-stearamide EBS (whose structural formula is

[0010]

[0011] In some embodiments, the halogen-free flame-retardant masterbatch contains, in terms of mass percentage, 20-70% of the carrier resin, 30-80% of the flame retardant, and 0.5-2.5% of the lubricant.

[0012] In some embodiments, the halogen-free flame-retardant masterbatch contains, in terms of mass percentage, 30-50% of the carrier resin, 50-70% of the flame retardant, and 0.5-2.5% of the lubricant.

[0013] In some embodiments, the halogen-free flame-retardant masterbatch contains, in terms of mass percentage, 10-55% of the alkyl phosphinate salt.

[0014] In some embodiments, the halogen-free flame-retardant masterbatch contains, in terms of mass percentage, 30-55% of the alkyl phosphinate salt.

[0015] In some embodiments, the alkyl phosphinate salt is selected from a combination of one or more of aluminum ethyl phosphinate, aluminum butyl phosphinate, aluminum diethyl phosphinate, aluminum dibutyl phosphinate, aluminum diisobutyl phosphinate, zinc diethyl phosphinate.

[0016] In some embodiments, the flame retardant further comprises a flame retardant synergist, the flame retardant synergist being at least one selected from melamine polyphosphate, aluminum phosphite, phenoxy cyclic phosphazene.

[0017] In some embodiments, when the flame retardant synergist contains melamine polyphosphate, the melamine polyphosphate accounts for 10-30% of the mass of the halogen-free flame-retardant masterbatch.

[0018] In some embodiments, when the flame retardant synergist contains aluminum phosphite, the aluminum phosphite is 5% to 25% by mass of the halogen-free flame-retardant master batch.

[0019] In some embodiments, when the flame retardant synergist contains phenoxy cyclic phosphazene, the phenoxy cyclic phosphazene is 1% to 5% by mass of the halogen-free flame-retardant master batch.

[0020] In some embodiments, the halogen-free flame-retardant master batch further comprises a char-forming synergist selected from the group consisting of one or more of a combination of zinc borate, pentaerythritol, dipentaerythritol, sorbitol, starch, triazine char-forming agents, polyamide char-forming agents, and phenolic resin char-forming agents.

[0021] In some embodiments, the char-forming synergist is 1% to 3% by mass of the halogen-free flame-retardant master batch.

[0022] In some embodiments, the halogen-free flame-retardant master batch further comprises an antioxidant.

[0023] In some embodiments, the antioxidant is selected from the group consisting of one or more of a combination of antioxidant 1010, antioxidant 1076, antioxidant 3114, antioxidant 3125, antioxidant 425, and antioxidant H10.

[0024] In some embodiments, the antioxidant is 0.3% to 3% by mass of the halogen-free flame-retardant master batch.

[0025] In some embodiments, the halogen-free flame-retardant master batch comprises the following components by mass percentage:

[0026] copolymer containing a non-polar saturated carbon chain segment and a polar ester segment 20% to 70%;

[0027] alkyl phosphinate salt 10% to 55%;

[0028] phenoxy cyclic phosphazene 1% to 5%;

[0029] lubricant 0.5% to 2.5%;

[0030] char-forming synergist 1% to 3%;

[0031] antioxidant 0.3% to 3%.

[0032] In some embodiments, the halogen-free flame-retardant master batch comprises the following components by mass percentage:

[0033] copolymer containing a non-polar saturated carbon chain segment and a polar ester segment 20% to 70%;

[0034] alkyl phosphinate salt 10% to 55%;

[0035] Melamine polyphosphate 10%~30%;

[0036] Phenoxy cyphos 1%~5%;

[0037] Lubricant 0.5%~2.5%;

[0038] Char-forming synergist 1%~3%;

[0039] Antioxidant 0.3%~3%.

[0040] In some embodiments, the halogen-free flame-retardant masterbatch comprises the following components by mass percentage:

[0041] Copolymer containing non-polar saturated carbon chain segment and polar ester segment 20%~70%;

[0042] Alkyl hypophosphite 10%~55%;

[0043] Aluminum phosphite 5%~25%;

[0044] Lubricant 0.5%~2.5%;

[0045] Char-forming synergist 1%~3%;

[0046] Antioxidant 0.3%~3%.

[0047] In some embodiments, the halogen-free flame-retardant masterbatch comprises the following components by mass percentage:

[0048] Copolymer containing non-polar saturated carbon chain segment and polar ester segment 20%~70%;

[0049] Alkyl hypophosphite 10%~55%;

[0050] Melamine polyphosphate 10%~30%;

[0051] Aluminum phosphite 5%~25%;

[0052] Lubricant 0.5%~2.5%;

[0053] Char-forming synergist 1%~3%;

[0054] Antioxidant 0.3%~3%.

[0055] The present application also provides a preparation method of the aforementioned halogen-free flame-retardant masterbatch, which comprises the steps of mixing, dispersing, melt-extruding, and granulating the raw materials.

[0056] The present application also provides a use of the aforementioned halogen-free flame-retardant masterbatch for flame-retardation of polybutylene terephthalate (PBT).

[0057] The application also provides a halogen-free flame-retardant PBT composite material, which comprises a PBT resin and the aforementioned halogen-free flame-retardant masterbatch.

[0058] In some embodiments, the PBT resin has an intrinsic viscosity of 0.8-1.0 dl / g. The intrinsic viscosity is tested according to the ISO 307 standard by means of an Ubbelohde viscometer method.

[0059] In some embodiments, the halogen-free flame-retardant PBT composite material further comprises a coupling agent and a filler.

[0060] In some embodiments, the coupling agent is selected from one or both of a silane coupling agent and a titanate coupling agent.

[0061] In some embodiments, the silane coupling agent is a KH550 silane coupling agent and / or a KH560 silane coupling agent.

[0062] In some embodiments, the filler is a reinforcing filler.

[0063] In some embodiments, the reinforcing filler is selected from a combination of one or more of glass fibers, basalt fibers, and carbon fibers.

[0064] In some embodiments, the reinforcing filler is a reinforcing filler treated with a coupling agent.

[0065] In some embodiments, the reinforcing filler is a reinforcing filler treated with an acrylate polymer.

[0066] In some embodiments, the acrylate polymer is a methyl methacrylate / butyl acrylate / acrylic acid copolymer.

[0067] In some embodiments, the halogen-free flame-retardant PBT composite material comprises, by weight parts, the following components: 40-85 parts of a PBT resin, 10-30 parts of a halogen-free flame-retardant masterbatch.

[0068] In some embodiments, the halogen-free flame-retardant PBT composite material comprises, by weight parts, the following components: 40-85 parts of a PBT resin, 10-30 parts of a halogen-free flame-retardant masterbatch, 0.1-4 parts of a coupling agent, and 20-40 parts of a filler.

[0069] In some embodiments, the halogen-free flame-retardant PBT composite material has an impact strength of 7-9 KJ / m 2 , a tensile strength of 85-100 MPa, a bending strength of 128-150 MPa, and a bending modulus of 8000-9000 MPa.

[0070] In some embodiments, the halogen-free flame-retardant PBT composite material has a vertical burning rating of V-0 and an oxygen index of 33% to 35.5%.

[0071] The present application also provides a method for preparing the aforementioned halogen-free flame-retardant PBT composite material, which comprises the steps of mixing, dispersing and melt-extruding the raw materials.

[0072] In some embodiments, the melt-extrusion is performed in a twin-screw extruder.

[0073] In some embodiments, the temperature of the twin-screw extruder is 230-250℃ in the first zone, 220-240℃ in the second zone, 215-235℃ in the third zone, 215-235℃ in the fourth zone, 210-230℃ in the fifth zone, 200-220℃ in the sixth zone, 200-220℃ in the seventh zone, 200-220℃ in the eighth zone, 200-220℃ in the ninth zone, and 210-230℃ in the tenth zone, from the main feeding port to the head.

[0074] In some embodiments, the length-diameter ratio of the twin-screw extruder is 48-52:1.

[0075] In some embodiments, the screw rotation speed of the twin-screw extruder is 350-550 rpm.

[0076] Compared with the prior art, the present application has the following advantages:

[0077] The halogen-free flame-retardant masterbatch of the present application can be used for the flame retardation of PBT, and can significantly improve the flame-retardant performance of PBT composite materials while ensuring good compatibility with PBT composite materials and the mechanical properties of PBT composite materials, and can achieve halogen-free flame retardation.

[0078] The halogen-free flame-retardant masterbatch of the present application can achieve a high concentration of flame retardant.

[0079] The halogen-free flame-retardant PBT composite material containing the halogen-free flame-retardant masterbatch of the present application has excellent mechanical properties and flame-retardant properties, and the impact strength can reach 8.94 KJ / m 2 , the tensile strength can reach 97.5 MPa, the bending strength can reach 145.6 MPa, the bending modulus can reach 8452 MPa, and the vertical burning rating is V-0 and the oxygen index can reach 35.5%. BRIEF DESCRIPTION OF DRAWINGS

[0080] Figure 1 The figure is the morphology of the flame-retardant masterbatch in Example 1.

[0081] Figure 2 The figure is the morphology of the flame-retardant masterbatch in Comparative Example 1.

[0082] Figure 3 The morphology of the flame-retardant masterbatch in Comparative Example 2;

[0083] Figure 4 The morphology of the flame-retardant masterbatch in Comparative Example 3;

[0084] Figure 5 The morphology of the flame-retardant masterbatch in Comparative Example 4. DETAILED DESCRIPTION

[0085] The present application provides an improved halogen-free flame-retardant masterbatch, the main innovation of the product is to use a copolymer containing a non-polar saturated carbon chain segment and a polar ester segment as a carrier resin, the non-polar saturated carbon chain segment in the carrier resin has flexibility, which can reduce the processing difficulty of the masterbatch, and the polar ester segment in the carrier resin is similar to the PBT resin matrix structure, both of which are ester structures, and they have strong mutual interaction and binding capacity, and will not appear interface repulsion, thereby improving the compatibility of the halogen-free flame-retardant masterbatch and the PBT matrix resin, ensuring the mechanical properties of the composite material, and also improving the concentration of the flame retardant in the halogen-free flame-retardant masterbatch. In the halogen-free flame-retardant masterbatch of the present application, the mass percentage concentration of the flame retardant can be as high as 70%.

[0086] Another innovation of the present application is that in the halogen-free flame-retardant masterbatch, a specific type of lubricant is used to improve the processing performance of the masterbatch and the compatibility with the PBT matrix resin when applied. The lubricant of the present application is a bisamide compound formed by saturated C12-18 acid and diamine, wherein the molecular chain has a saturated non-polar long carbon chain structure at both ends and a polar bisamide structure in the middle. The excellent wetting and penetration ability given by this symmetrical median polarity structure improves the material processing performance and increases the melt flowability, thereby preparing a high-concentration flame-retardant masterbatch, and the concentration of the flame retardant powder in the masterbatch is very high, which is difficult to achieve by ordinary prior art.

[0087] Another innovation of the present application is to use a flame retardant synergist to synergize the flame retardant effect of the alkyl hypophosphite salt, the flame retardant synergist being at least one selected from melamine polyphosphate, aluminum phosphite and phenoxy cyclic phosphazene. Among them, the high oxidation state phosphorus in phenoxy cyclic phosphazene, alkyl hypophosphite salt and aluminum phosphite can play a condensed phase flame retardant effect during combustion, that is, when phosphorus generates phosphoric acid compounds during combustion, these phosphoric acid compounds act as dehydrating agents, and the multi-carbon structure of phenoxy cyclic phosphazene promotes the dehydration and carbonization of polymers, thereby avoiding the generation of flammable gases; and the benzene ring in phenoxy cyclic phosphazene has high thermal stability and can absorb heat during combustion, while the carbon layer structure separates air and heat from the surface of the burning material, which can effectively prevent the continuation of combustion. In addition, the nitrogen elements contained in phenoxy cyclic phosphazene and melamine polyphosphate can release non-combustible gas N2 under high temperature conditions, and these gases can dilute flammable gases and oxygen, thereby inhibiting the combustion reaction. In addition, nitrogen elements can also interrupt the combustion chain reaction by capturing free radicals in the combustion process, thereby playing a flame-retardant effect.

[0088] The present application will be further described below in conjunction with examples. However, the present application is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to different specific requirements, and the implementation conditions not specified are the conventional conditions in the industry. The technical features involved in each embodiment of the present application can be combined with each other as long as they do not conflict with each other.

[0089] Example 1

[0090] The present embodiment provides a high-concentration enhanced halogen-free flame-retardant master batch, the mass fractions of its raw materials are shown in Table 1 below, and its preparation process is as follows:

[0091] (1) First, heat the high-speed mixer to 90℃, then weigh and mix the raw materials except for ethylene-methyl acrylate copolymer into the high-speed mixer, the mixing time is 20 min, and the mixing speed is 1000 revolutions / minute.

[0092] (2) The mixture obtained in step (1) and ethylene-methyl acrylate copolymer are respectively added to a twin-screw extruder through a precision metering feeder for mixing, dispersion, melt extrusion, and pelletization to prepare a flame-retardant master batch.

[0093] In step (2), the temperature of the twin-screw extruder from the main feeding port to the die is 180℃, the temperature of the second zone is 180℃, the temperature of the third zone is 175℃, the temperature of the fourth zone is 175℃, the temperature of the fifth zone is 160℃, the temperature of the sixth zone is 160℃, the temperature of the seventh zone is 160℃, the temperature of the eighth zone is 150℃, the temperature of the ninth zone is 150℃, the temperature of the tenth zone is 170℃, and the screw rotation speed is 350 revolutions / minute.

[0094] The above flame-retardant master batch is used to prepare a halogen-free flame-retardant PBT composite material:

[0095] (1) Put 44.5% PBT resin (intrinsic viscosity 0.9 dl / g), 25% above flame-retardant masterbatch, 0.5% KH550 coupling agent, 30% glass fiber (methyl methacrylate / butyl acrylate / acrylic acid copolymer treated glass fiber) into a high-speed mixer according to mass percentage, mix for 10 min, and the mixing speed is 900 rpm.

[0096] (2) Put the mixture obtained in step (1) into a twin-screw extruder through the main feeding port, and carry out mixing, dispersion, melt extrusion and pelletization.

[0097] In step (2), the temperature of the twin-screw extruder from the main feeding port to the die head is 240°C, the temperature of the second zone is 235°C, the temperature of the third zone is 235°C, the temperature of the fourth zone is 230°C, the temperature of the fifth zone is 230°C, the temperature of the sixth zone is 220°C, the temperature of the seventh zone is 220°C, the temperature of the eighth zone is 210°C, the temperature of the ninth zone is 210°C, the temperature of the tenth zone is 230°C, and the screw speed is 450 rpm. The test sample is injection molded at 255°C by an injection molding machine.

[0098] Examples 2-9

[0099] This example provides a high-concentration enhanced halogen-free flame-retardant masterbatch, which is used to prepare a halogen-free flame-retardant PBT composite. The difference from Example 1 is only that the raw material composition and amount are different. See Table 1 for details.

[0100] Example 10

[0101] The difference from Example 2 is only that when preparing the halogen-free flame-retardant PBT composite, the raw material composition is adjusted to 51.5% PBT resin, 18% flame-retardant masterbatch, 0.5% KH560 coupling agent, and 30% methyl methacrylate / butyl acrylate / acrylic acid copolymer treated glass fiber according to mass percentage.

[0102] Comparative Example 1

[0103] This comparative example provides a high-concentration enhanced halogen-free flame-retardant masterbatch, which is used to prepare a halogen-free flame-retardant PBT composite. The difference from Example 2 is only that the raw material ethylene-methyl acrylate copolymer of the flame-retardant masterbatch is replaced by PBT resin.

[0104] Comparative Example 2

[0105] This comparative example provides a high-concentration enhanced halogen-free flame-retardant masterbatch, which is used to prepare a halogen-free flame-retardant PBT composite. The difference from Example 2 is only that the raw material ethylene-methyl acrylate copolymer of the flame-retardant masterbatch is replaced by polyethylene resin.

[0106] Comparative Example 3

[0107] This comparative example provides a high-concentration enhanced halogen-free flame-retardant masterbatch, and uses it to prepare a halogen-free flame-retardant PBT composite material, which is basically the same as Example 2, with the only difference being that the raw material ethylene bis-stearamide EBS of the flame-retardant masterbatch is replaced by ethylene bis-oleic amide EBO.

[0108] Comparative Example 4

[0109] This comparative example provides a high-concentration enhanced halogen-free flame-retardant masterbatch, and uses it to prepare a halogen-free flame-retardant PBT composite material, which is basically the same as Example 2, with the only difference being that the raw material ethylene bis-stearamide EBS of the flame-retardant masterbatch is replaced by octadecyl alcohol (stearyl alcohol).

[0110] Comparative Example 5

[0111] This comparative example provides a halogen-free compound powder flame-retardant agent, and uses it to prepare a halogen-free flame-retardant PBT composite material, according to weight parts, the raw materials of the flame-retardant agent are: aluminum diethyl phosphinate 572 parts, melamine polyphosphate 143 parts, aluminum phosphite 207 parts, phenoxy cyclic phosphazene 36 parts, ethylene bis-stearamide EBS 14 parts, anhydrous zinc borate 21 parts, and antioxidant H10 7 parts; the preparation method of the flame-retardant agent is: first, heat the high-speed mixer to 90°C, then weigh and mix the raw materials in the high-speed mixer, the mixing time is 20 min, and the mixing speed is 1000 revolutions / minute, to obtain the halogen-free compound powder flame-retardant agent.

[0112] Preparation of a halogen-free flame-retardant PBT composite material: basically the same as Example 2, with the only difference being that the flame-retardant masterbatch in Example 2 is replaced by the halogen-free compound powder flame-retardant agent of this comparative example.

[0113] Table 1

[0114]

[0115] In Table 1, the ethylene-methyl acrylate copolymer is: 29MA03T. " / " represents no.

[0116] The mechanical properties and flame-retardant properties of the PBT composite materials of each example and comparative example are tested by methods such as impact strength (GB / T1843-2008), bending strength (GB / T9341-2008), tensile strength (GB / T1040.2-2006), oxygen index (GB / T2406.2-2009), vertical burning (GB / T2408-2008), and the results are shown in Table 2.

[0117] Table 2

[0118]

[0119] The morphology of the flame-retardant masterbatch of Example 1, Comparative Examples 1-4 is shown in FIG. 1, respectively. As shown, the flame-retardant masterbatch of Example 1 using the solution of the present application is in the form of particles and has good formability, while the flame-retardant masterbatch of Comparative Examples 1-4 not using the specific types of carrier resin and lubricant of the present application either cannot be obtained in the form of particles and is still in the form of powder, or the particles prepared have black fine lines on the side surface, affecting the appearance and performance. Figures 1-5 Figure 4 Figure 5

[0120] As can be seen from the comparison of Example 1 and Comparative Examples 1-2, when the specific type of carrier resin of the present application is not used, the flame-retardant masterbatch obtained has low flame-retardant efficiency and poor mechanical properties when used in PBT materials due to poor compatibility. As can be seen from the comparison of Example 1 and Comparative Examples 3-4, when the specific type of lubricant of the present application is not used, the flame-retardant masterbatch obtained has poor mechanical properties when used in PBT materials due to poor dispersibility. As can be seen from the comparison of Example 2 and Comparative Example 5, the flame-retardant masterbatch is easier to process and disperse into the material than the traditional powder flame-retardant agent, and the flame-retardant performance and mechanical properties are improved.

[0121] As can be seen, the halogen-free flame-retardant masterbatch of the present application can ensure the mechanical properties of PBT composite materials when used in PBT materials, while significantly improving the flame-retardant properties, such as vertical burning grade and oxygen index, etc. The flame-retardant masterbatch of the present application is halogen-free and more environmentally friendly.

[0122] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and principle of the present application should be covered within the protection scope of the present application.

[0123] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited. The ranges or values should be interpreted as being approximate, meaning values near (for example, 10% of) the recited values are also within the scope of the ranges or values. The endpoints of the ranges of values (for example, the upper and lower taxonomic ranks) as well as the individual values are not to be construed as inscribed points, but rather as signposts. The recited ranges of values are therefore to be interpreted to include single values and sub-ranges of the endpoints as well as the individual values.​​​

Claims

1. A halogen-free flame retardant masterbatch, characterized by: According to the mass percentage, the halogen-free flame retardant masterbatch comprises the following components: 30% to 50% of copolymer, 30% to 55% of alkyl phosphinate, 0.5% to 2.5% of lubricant, and 1% to 3% of char-forming synergist zinc borate; the copolymer is selected from one or more combinations of ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-butyl acrylate copolymer, and ethylene-butyl methacrylate copolymer; the lubricant is ethylene bisstearamide; The halogen-free flame retardant masterbatch also includes a flame retardant synergist, which is selected from at least one of melamine polyphosphate, aluminum phosphite, and phenoxy cyclophosphazene; when the flame retardant synergist contains melamine polyphosphate, the melamine polyphosphate accounts for 10% to 30% of the mass of the halogen-free flame retardant masterbatch; when the flame retardant synergist contains aluminum phosphite, the aluminum phosphite accounts for 5% to 25% of the mass of the halogen-free flame retardant masterbatch; when the flame retardant synergist contains phenoxy cyclophosphazene, the phenoxy cyclophosphazene accounts for 1% to 5% of the mass of the halogen-free flame retardant masterbatch.

2. The halogen-free flame retardant masterbatch according to claim 1, characterized in that: The alkyl phosphinate is selected from one or more of ethyl phosphinate aluminum, butyl phosphinate aluminum, diethyl phosphinate aluminum, dibutyl phosphinate aluminum, diisobutyl phosphinate aluminum, and diethyl zinc phosphinate.

3. The halogen-free flame retardant masterbatch according to claim 1, characterized in that: The halogen-free flame retardant masterbatch further comprises an antioxidant.

4. The halogen-free flame retardant masterbatch according to claim 3, characterized in that: The antioxidant is selected from one or more combinations of antioxidant 1010, antioxidant 1076, antioxidant 3114, antioxidant 3125, antioxidant 425, and antioxidant H10.

5. The halogen-free flame retardant masterbatch according to claim 3, characterized in that: The antioxidant accounts for 0.3% to 3% of the mass of the halogen-free flame retardant masterbatch.

6. The halogen-free flame retardant masterbatch according to claim 1, characterized in that: The halogen-free flame retardant masterbatch comprises the following components in terms of mass percentage: Copolymer 30% to 50%; Alkyl phosphinate 30% to 55%; Phenoxy cyclophosphazene 1% to 5%; Lubricant 0.5% to 2.5%; Carbon-forming synergist zinc borate 1% to 3%; Antioxidant 0.3%~3%.

7. The halogen-free flame retardant masterbatch according to claim 1, characterized in that: The halogen-free flame retardant masterbatch comprises the following components in terms of mass percentage: Copolymer 30% to 50%; Alkyl phosphinate 30% to 55%; Melamine polyphosphate 10% to 30%; Phenoxy cyclophosphazene 1% to 5%; Lubricant 0.5% to 2.5%; Carbon-forming synergist zinc borate 1% to 3%; Antioxidant 0.3%~3%.

8. The halogen-free flame retardant masterbatch according to claim 1, characterized in that: The halogen-free flame retardant masterbatch comprises the following components in terms of mass percentage: Copolymer 30% to 50%; Alkyl phosphinate 30% to 55%; Aluminum phosphite 5% to 25%; Lubricant 0.5% to 2.5%; Carbon-forming synergist zinc borate 1% to 3%; Antioxidant 0.3%~3%.

9. The halogen-free flame retardant masterbatch according to claim 1, characterized in that: The halogen-free flame retardant masterbatch comprises the following components in terms of mass percentage: Copolymer 30% to 50%; Alkyl phosphinate 30% to 55%; Melamine polyphosphate 10% to 30%; Aluminum phosphite 5% to 25%; Lubricant 0.5% to 2.5%; Carbon-forming synergist zinc borate 1% to 3%; Antioxidant 0.3%~3%.

10. A method for preparing the halogen-free flame retardant masterbatch according to any one of claims 1 to 9, characterized in that: The preparation method comprises the steps of mixing, dispersing, melt-extruding and pelletizing the raw materials.

11. Use of the halogen-free flame retardant masterbatch according to any one of claims 1 to 9 for flame retardant polybutylene terephthalate (PBT).

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