Hydroxyl-containing DOPO composite flame retardant, and preparation method therefor and use thereof

Abstract

Provided in the present invention is a hydroxyl-containing DOPO composite flame retardant, comprising a component A having the structure of formula (I) and a component B having the structure of formula (II). In the hydroxyl-containing DOPO composite flame retardant, the content of the component A is larger than or equal to 50 wt%, but smaller than 100 wt%, and the content of the component B is larger than 0 wt%, but smaller than or equal to 50 wt%. The composite flame retardant composed of the component A and the component B achieves the integration of high flame retardance and high physical properties in a flame-retardant material, and overcomes the defects that using the component B alone leads to low flame-retardant efficiency and that using the component A alone results in deterioration in the mechanical properties of a high polymer material.

Description

A DOPO-type composite flame retardant containing hydroxyl group, preparation method and application thereof Technical Field

[0001] The invention belongs to the technical field of flame retardant preparation, and relates to a hydroxyl-containing DOPO composite flame retardant, a preparation method and application thereof. Background Art

[0002] With the rapid rise of polymer materials science, polymers have become widely used in human production and daily life. Since most polymers are flammable, fires caused by their ignition are increasing, and therefore the flame retardant properties of polymers have garnered widespread attention. Polymers themselves cannot meet the requirements of flame retardant regulations, and flame retardants are often added to achieve this. Recently, due to environmental protection needs, halogen-free flame retardants, such as phosphorus-based flame retardants, have seen significant development. In particular, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and its derivatives have attracted attention due to their high flame retardant efficiency, low toxicity, and minimal impact on polymer performance.

[0003] Currently reported DOPO derivatives can be structurally divided into reactive and additive types: reactive derivatives have reactive groups such as carboxyl and hydroxyl groups on the phosphorus atom substituents, while additive derivatives are structurally inert and lack reactive functional groups.

[0004] Chinese patent publication CN100366627C reports on a DiDOPO with a hydroxyalkyl-substituted vinylene bridge structure. The hydroxyl group is far away from the phosphorus atom and has high reactivity, allowing it to undergo ester exchange reactions with carboxylic acids or esters. Chinese patent publication CN104086593B reports on the preparation of DiDOPO with a phenylene bridge structure by the addition of semi-aryl ketones and DOPO. The reaction process first involves the reaction of DOPO and the ketone group to form an α-hydroxyphosphine compound, which is then dehydrated under heat to form a vinylphosphonate, thereby introducing a second DOPO. Chinese patent publication CN106366128B uses the hydroxyl group of the α-hydroxyphosphine compound to introduce an allyloxy group. The hydroxyl group is highly reactive, and the patent specifically points out that phosphophananthenanthrene compounds containing hydroxyl groups are not suitable for low dielectric systems (dielectric loss less than 0.010). From this patent, it can be seen that introducing a hydroxyl group is not an option unless it is for the purpose of reaction.

[0005] Japanese patent publications JPH11-106619, JP2001270993, and Chinese patent publication CN102428091B report on DiDOPO with an inert bridge structure that lacks reactive functional groups. PCT patent WO2013020696A2 and Chinese patent publication CN109851639B report on DOPO derivatives containing P-N bonds. These derivatives can be used as additive flame retardants.

[0006] Existing reactive DOPO derivatives need to be further reacted with polymers or monomers before use, which is not conducive to the flame retardant modification of existing polymer materials. Moreover, due to the different reactivity between polymers or monomers, the performance is difficult to control and the cost is high. Additive DOPO derivatives have a greater impact on the physical properties of flame retardant polymer materials. For example, US Patent US8536256B2 mentions that the introduction of DiDOPO with a vinylidene bridge structure can increase the T g Reducing the temperature from 163-172°C to 126-131°C makes it difficult to meet the requirements of lead-free welding, limiting its application areas; Chinese patent CN106366128B mentions that the presence of hydroxyl groups is detrimental to the dielectric loss factor (Df) of flame-retardant polymer materials, making them difficult to use in low dielectric loss copper-clad laminates.

[0007] Based on the above analysis, existing reactive and additive DOPO derivatives still struggle to meet the requirements for thermal and chemical stability, as well as minimal impact on the physical properties of flame-retardant polymers. Furthermore, the preparation process for existing DOPO derivatives is complex and costly. There is a continued desire to develop a flame retardant with a simple preparation process, high atom efficiency, excellent flame retardancy, minimal impact on the physical properties of flame-retardant polymers, and even the ability to improve the electrical properties of the flame-retardant system.

[0008] Summary of the Invention

[0009] The present invention aims to address the shortcomings of the prior art by providing a hydroxyl-containing DOPO-based composite flame retardant, a preparation method thereof, and flame-retardant applications in polymer materials. The hydroxyl-containing DOPO-based composite flame retardant has a simple preparation method, high atom efficiency, good flame retardancy, and retains the excellent physical properties of polymer materials.

[0010] The first object of the present invention is achieved through the following technical solutions:

[0011] A hydroxyl-containing DOPO composite flame retardant, comprising component A having a structure of formula (I) and component B having a structure of formula (II).

[0012] Wherein, R1 and R2 are independently selected from C1 to C 18 The alkylene group, any hydrogen atom on the alkylene group can be independently replaced by a C1 to C8 alkyl group, a C6 to C 18 aromatic substitution;

[0013] R3 and R4 are independently selected from hydrogen, C1-C 18 Alkyl, C3~C 18 Heteroaryl, C6~C 24Any hydrogen atom on the aromatic ring of the aromatic or heteroaryl group can be independently replaced by any C1 to C 18 Alkyl substitution;

[0014] x and y are independently selected from 0, 1, 2, 3, and 4.

[0015] Preferably, R1 and R2 are independently selected from C1-C8 alkylene groups, and any hydrogen atom on the alkylene group may be independently substituted with a C1-C8 alkyl group. Further preferably, R1 and R2 are independently selected from methylene, ethylene, propylene, butylene, methyl-substituted methylene, dimethyl-substituted methylene, ethyl-substituted methylene, methyl-substituted ethylene, dimethyl-substituted ethylene, methyl-substituted propylene, dimethyl-substituted propylene, or propyl-substituted propylene.

[0016] Preferably, R3 and R4 are independently selected from hydrogen, C1-C8 alkyl, C3-C 18 Heteroaryl, C6~C 18 Further preferably, R3 and R4 are independently hydrogen, methyl, or ethyl. Alternatively, R3 and R4 are hydrogen.

[0017] Preferably, x=y=0.

[0018] In the hydroxyl-containing DOPO composite flame retardant, 50 wt% ≤ the content of component A < 100 wt%, and 0 wt% < the content of component B ≤ 50 wt%. In the present invention, wt% means weight percentage.

[0019] Preferably, the total amount of component A and component B is 100wt%, 50wt%≤the content of component A<100wt%. When it is lower than 50wt%, the flame retardant performance of the hydroxyl-containing DOPO composite flame retardant composed of component A and component B (hereinafter referred to as "mixture C") decreases. The content of component A can be arbitrarily selected from any value among 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, 95wt%, 96wt%, 97wt%, 98wt%, 99wt%, 99.1wt%, 99.2wt%, 99.3wt%, 99.4wt%, 99.5wt%, 99.6wt%, 99.7wt%, 99.8wt%, 99.9wt%, 99.99wt%, 99.9999wt%, 99.99999wt% or any range value between two of them.

[0020] Experiments surprisingly revealed that the addition of component B can improve the physical properties of flame-retardant polymer materials. However, the content of component B must be ≤ 50 wt%. When the content of component B exceeds 50 wt%, the flame retardant effect of mixture C decreases. Flame retardancy and physical properties are typically a conflict for flame-retardant materials. However, within the scope of the present invention, mixture C, composed of components A and B, unexpectedly achieves both high flame retardancy and excellent physical properties.

[0021] Preferably, in the hydroxyl-containing DOPO composite flame retardant, the content of component A is 65 wt% or less and less than 100 wt%, and the content of component B is 0 wt% or less and less than 35 wt%. More preferably, the content of component A is 82 wt% or less and less than 100 wt%, and the content of component B is 0 wt% or less and less than 18 wt%. More preferably, the content of component A is 90 wt% or less and less than 100 wt%, and the content of component B is 0 wt% or less and less than 10 wt%. Most preferably, the content of component A is 97 wt% or less and less than 100 wt%, and the content of component B is 0 wt% or less and less than 3 wt%.

[0022] The second object of the present invention is achieved through the following technical solutions:

[0023] A method for preparing a hydroxyl-containing DOPO composite flame retardant comprises the following steps:

[0024] reacting a compound having a structure of formula (III) with an aliphatic cyclic diketone compound having a structure of formula (IV), controlling the reaction conditions, and purifying after the reaction to obtain a mixed product of component A having a structure of formula (I) and component B having a structure of formula (II);

[0025] Wherein, R3 and R4 have the same meaning as R3 and R4 in formula (I) and formula (II), that is, they are independently selected from hydrogen, C1-C 18 Alkyl, C3~C 18 Heteroaryl, C6~C 24 Any hydrogen atom on the aromatic ring of the aromatic or heteroaryl group can be independently replaced by any C1 to C 18 Alkyl substitution;

[0026] x and y have the same meanings as those defined in formula (I) and formula (II), i.e., they are independently selected from 0, 1, 2, 3, 4;

[0027] Wherein, R1 and R2 have the same meaning as R1 and R2 in formula (I) and formula (II), that is, they are independently selected from C1 to C 18 The alkylene group, any hydrogen atom on the alkylene group can be independently replaced by a C1 to C8 alkyl group, a C6 to C18 of aromatic substitution.

[0028] Preferably, the compound having the structure of formula (III) is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), that is, in formula (III), x and y are 0.

[0029] Optionally, the aliphatic cyclic diketone compound having the structure of formula (IV) includes but is not limited to one or more of cyclohexanedione, cyclobutanedione, cyclopentanedione, cycloheptanedione, cyclooctanedione, methylcyclohexanedione, dimethylcyclohexanedione, propylcyclohexanedione, tetramethylcyclobutanedione, methylcyclopentanedione, dimethylcyclopentanedione, and ethylcyclopentanedione. Preferably, the aliphatic cyclic diketone compound having the structure of formula (IV) is one or more of cyclohexanedione, methylcyclohexanedione, dimethylcyclohexanedione, cyclopentanedione, and cycloheptanedione. Further preferably, the aliphatic cyclic diketone compound having the structure of formula (IV) is one or more of 1,4-cyclohexanedione, 1,3-cyclohexanedione, 5,5-dimethyl-1,3-cyclohexanedione, and cyclopentanedione. Most preferably, it is 1,4-cyclohexanedione.

[0030] In the mixture C of component A having a structure of formula (I) and component B having a structure of formula (II), the contents of component A and component B can be controlled by the molar ratio of the aliphatic cyclic diketone compound having a structure of formula (IV) to the compound having a structure of formula (III), the reaction time, the purification method, and the like.

[0031] Preferably, the present invention controls the molar ratio of the aliphatic cyclic diketone compound having the structure of formula (IV) to the compound having the structure of formula (III), the reaction time, the purification method, etc., so that in the mixed product, the content of component A is 50wt%≤<100wt%, and the content of component B is 0wt%<≤50wt%.

[0032] Preferably, when the compound having the structure of formula (III) and the aliphatic cyclic diketone compound having the structure of formula (IV) are reacted, the molar ratio of the compound having the structure of formula (III) to the aliphatic cyclic diketone compound having the structure of formula (IV) is 1.5 to 10:1. More preferably, it is 1.5 to 5:1, and even more preferably, it is 1.5 to 3.0:1. If the molar ratio of the two compounds is too high, the compound having the structure of formula (III) is excessive, resulting in low raw material utilization and reduced economic efficiency. If the molar ratio is too low, the content of component B is too high, which is not conducive to flame retardancy.

[0033] Preferably, the reaction time of the compound having the structure of formula (III) and the aliphatic cyclic diketone compound having the structure of formula (IV) is 0.01 to 25 hours. More preferably, it is 0.1 to 20 hours, and even more preferably, it is 0.5 to 10 hours. If the reaction time is too short, the content of component B is too high, which is not conducive to flame retardancy. On the other hand, if the reaction time is too long, production efficiency is low and production costs are increased.

[0034] Generally speaking, when the molar ratio of the compound having the structure of formula (III) to the aliphatic cyclic diketone compound having the structure of formula (IV) is too low, the content of component B can be reduced by appropriately extending the reaction time and adjusting the content of component B within a suitable range to reduce production costs while ensuring the flame retardant efficiency of the mixed product C.

[0035] Preferably, when reacting the compound having the structure of formula (III) and the aliphatic cyclic diketone compound having the structure of formula (IV), the reaction temperature is room temperature to 250°C. More preferably, it is 50 to 220°C, and even more preferably, it is 80 to 200°C. If the reaction temperature is too high, the compound having the structure of formula (III) tends to thermally degrade; while if the reaction temperature is too low, the reaction rate is too slow, resulting in poor economic efficiency.

[0036] When the compound having the structure of formula (III) and the aliphatic cyclic dione compound having the structure of formula (IV) react, the reaction can be carried out in the absence of a solvent or in an inert solvent. Solvent-free means that no other solvent is added to the reactants, but the excess reactants are used as solvents. For example, when a large amount of compound having the structure of formula (III) is added, in addition to a portion of the compound reacting with the aliphatic cyclic dione having the structure of formula (IV), the excess compound having the structure of formula (III) can be used as a solvent. The inert solvent can be listed as one or more conventional solvents including aromatic hydrocarbons, alkanes, alcohols, esters, etc.; optionally, the inert solvent is selected from at least one of toluene, xylene, and trimethylbenzene.

[0037] When the compound having the structure of formula (III) and the aliphatic cyclic diketone compound having the structure of formula (IV) react, the reaction can be carried out under normal pressure, positive pressure or negative pressure.

[0038] When the compound with formula (III) structure and the aliphatic cyclic diketone compound with formula (IV) structure react, it is unexpected that the reaction can be carried out without an added catalyst. The phosphine hydrogenation reaction of the general pH bond addition to the ketone group, i.e., the Pudovik reaction, requires an alkaline or acidic catalyst. However, when the compound with formula (III) structure and the aliphatic cyclic diketone compound with formula (IV) structure react, an added catalyst is unnecessary, which greatly reduces the cost of removing the catalyst and greatly improves economic efficiency. Of course, the reaction can also be carried out in the presence of a catalyst, and the catalyst can be any catalyst applied to the Pudovik reaction, such as one or more of titanate, organic amine, inorganic base, fatty alcohol aluminum, etc. Preferably, the reaction is carried out without an added catalyst.

[0039] After the reaction is complete, the product is purified to remove unreacted products and impurities to obtain hydroxyl-containing DOPO composite flame retardants having the structure of formula (I) and the structure of formula (II). The purification method includes conventional methods such as solvent washing and recrystallization. Optionally, after the reaction is completed, the product is subjected to solvent washing. Optionally, the solvent used in the solvent washing is a good solvent for the compound having the structure of formula (III) and / or the aliphatic cyclic diketone compound having the structure of formula (IV). Optionally, the solvent used in the solvent washing is selected from at least one of alcohols, esters, ethers, alkanes, and aromatic hydrocarbons. Optionally, the solvent used in the solvent washing is selected from at least one of ethanol, isopropanol, toluene, and p-xylene.

[0040] The third object of the present invention is achieved through the following technical solutions:

[0041] A method for preparing a hydroxyl-containing DOPO composite flame retardant comprises the following steps: physically mixing component A having a structure of formula (I) and component B having a structure of formula (II), wherein in the mixture, the content of component A is 50 wt% ≤ < 100 wt%, and the content of component B is 0 wt% < ≤ 50 wt%.

[0042] The contents of component A and component B can be obtained by reacting the compound having the structure of formula (III) and the aliphatic cyclic diketone compound having the structure of formula (IV), respectively.

[0043] Specifically, the preparation method of component A having a structure represented by formula (I) includes the following steps: reacting a compound having a structure represented by formula (III) and an aliphatic cyclic diketone compound having a structure represented by formula (IV), controlling the molar ratio of the aliphatic cyclic diketone compound having a structure represented by formula (IV) to the compound having a structure represented by formula (III) to be ≤0.5, and regulating the reaction time, purification method, and other methods so that the product is a pure component A having a structure represented by formula (I).

[0044] The preparation method of component B having a structure represented by formula (II) comprises the following steps: reacting a compound having a structure represented by formula (III) and an aliphatic cyclic diketone compound having a structure represented by formula (IV), controlling the molar ratio of the aliphatic cyclic diketone compound having a structure represented by formula (IV) to the compound having a structure represented by formula (III) to be ≥1, and regulating the reaction time, purification method, and other methods so that the product is a pure component B having a structure represented by formula (II).

[0045] How to control the molar ratio, reaction time, and purification method to obtain component A and component B respectively can be designed according to specific circumstances.

[0046] The fourth object of the present invention is achieved through the following technical solutions:

[0047] A flame retardant polymer material comprises the hydroxyl-containing DOPO composite flame retardant and a polymer material.

[0048] Preferably, the flame retardant polymer material comprises 1 to 50 wt% of the hydroxyl-containing DOPO composite flame retardant and 50 to 99 wt% of a polymer material.

[0049] Optionally, the mass fraction of the hydroxyl-containing DOPO composite flame retardant in the flame retardant polymer material is 1-50wt%, further 1-45wt%, further 1-40wt%, further 2-50wt%, further 2-45wt%, further 2-40wt%, further 3-50wt%, further 3-45wt%, further 3-40wt%, further 5-35wt%, further 3-30wt%, further 5-30wt%, further 5-25wt%, further 8-30wt%, further 10-30wt%, further 12-30wt%. All values ​​not listed within the above numerical ranges are applicable.

[0050] Specifically, the amount of the hydroxyl-containing DOPO composite flame retardant used depends on the structure of the polymer material and the flame retardant effect to be achieved.

[0051] The polymer material is selected from one or more of thermoplastic resins and thermosetting resins.

[0052] The thermoplastic resin is at least one selected from polybutadiene, polyamide, polyester, polyphenylene ether, acrylonitrile-butadiene-styrene copolymer, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyimide, polyphenylene sulfide, and polyetheretherketone.

[0053] The thermosetting resin is selected from at least one of vinyl polyphenylene ether resin, epoxy resin, cyanate resin, BT resin, bismaleimide resin, phenolic resin, polyurethane resin, thermosetting polyimide, unsaturated polyester resin, vinyl resin, benzoxazine resin, arylacetylene resin, and furan resin. Preferably, the thermosetting resin is at least one of vinyl polyphenylene ether resin, epoxy resin, cyanate resin, BT resin, bismaleimide resin, and thermosetting polyimide. More preferably, the thermosetting resin is at least one of vinyl polyphenylene ether resin and epoxy resin.

[0054] The vinyl polyphenylene ether resin refers to a polyphenylene ether resin having an unsaturated double bond in the end-capping group. Optionally, the vinyl polyphenylene ether resin is selected from at least one of Mitsubishi Gas's OPE-2st and SABIC's SA-9000.

[0055] Preferably, the epoxy resin is selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, dicyclopentadiene epoxy resin, biphenyl epoxy resin or naphthol epoxy resin.

[0056] Optionally, the mass fraction of the polymer material in the flame retardant polymer material is 50-99wt%, further 50-90wt%, further 50-80wt%, further 50-70wt%, further 50-60wt%, further 55-99wt%, further 55-90wt%, further 55-80wt%, further 55-70wt%, further 60-90wt%, further 65-85wt%. All values ​​not listed within the above numerical ranges are applicable.

[0057] Optionally, the flame retardant polymer material further includes functional additives, which can be selected from at least one of a reinforcing agent, an anti-dripping agent, a stabilizer, a pigment, a dye, a carbonizing catalyst, a dispersant, a nucleating agent, an inorganic filler, an organic filler, and an antioxidant.

[0058] The reinforcing agent may be exemplified by glass fiber.

[0059] The anti-dripping agent may be a polytetrafluoroethylene-based anti-dripping agent.

[0060] Preferably, the inorganic filler is selected from at least one of silicon dioxide, mica, calcium carbonate, aluminum oxide, aluminum nitride, talc, calcium oxide, calcium silicate, glass fiber powder, and silica. Preferably, the inorganic filler is silicon dioxide. Further preferably, the median particle size D of the silicon dioxide is 50 1~15μm.

[0061] Preferably, the organic filler is selected from at least one of polytetrafluoroethylene powder, polyphenylene sulfide powder and polyethersulfone powder.

[0062] Optionally, the mass fraction of the functional additive in the flame retardant polymer material is 5-40 wt %, further 5-35 wt %, further 5-30 wt %, further 5-25 wt %, further 5-20 wt %, further 10-35 wt %, further 15-35 wt %, further 20-35 wt %. All values ​​not listed in the above numerical ranges are applicable.

[0063] Optionally, the flame retardant polymer material further includes a flame retardant Q, and the flame retardant Q is selected from at least one of a phosphorus-based flame retardant, a nitrogen-based flame retardant, and a boron-based flame retardant.

[0064] Preferably, the phosphorus-based flame retardant is at least one selected from bisphosphate flame retardants, phosphazene flame retardants, dialkyl phosphinates, DOPO derivatives, and phosphine oxide compounds.

[0065] Furthermore, the bisphosphate flame retardant is selected from at least one of bisphenol A bisdiphenyl phosphate, resorcinol bisdiphenyl phosphate, and 1,3-phenylene (2,6-xylyl) tetraphosphate.

[0066] Furthermore, the phosphazene flame retardant is selected from at least one of hexaphenoxycyclotriphosphazene, cyanophenoxyphosphazene (such as FP-300 of Fushimi Pharmaceutical Co., Ltd. of Japan), allyl cyclophosphazene (such as SPV-100 of Otsuka of Japan), and cyclic biphenyloxyphosphazene (such as BP-PZ of Otsuka of Japan).

[0067] Furthermore, the dialkyl phosphinate is at least one selected from the group consisting of aluminum diethylphosphinate, aluminum diisobutylphosphinate, aluminum dipropylphosphinate, and zinc diethylphosphinate.

[0068] Furthermore, the DOPO derivative is selected from at least one of 6H-dibenzo[c,e][1,2]oxophosphoglycerate, 6,6'-(1,2-ethanediyl)bis-6,6'-dioxide, 6H-dibenzo[c,e][1,2]oxane-6,6'-(1,4-ethanediyl)bis-,6,6'-dioxide, and 6H-dibenzo[c,e][1,2]oxane-6,6'-(1,4-phenylethanediyl)bis-6,6'-dioxide (such as HTP-6123 of Guizhou Yuanyi Group).

[0069] Furthermore, the phosphine oxide compound is p-xylylbisdiphenylphosphine oxide (such as PQ-60 from Jinyi Chemical).

[0070] Preferably, the nitrogen-based flame retardant is selected from at least one of melamine cyanurate, melamine polyphosphate, and ammonium polyphosphate;

[0071] Preferably, the boron-based flame retardant is selected from zinc borate.

[0072] Optionally, the mass fraction of the flame retardant Q in the flame retardant polymer material is 0.5-20 wt %, further 0.5-15 wt %, further 0.5-10 wt %, further 1-20 wt %, further 1-18 wt %, further 1-13 wt %, further 2-19 wt %, further 2-14 wt %, further 3-16 wt %, further 4-17 wt %, further 5-12 wt %. All values ​​not listed within the above numerical ranges are applicable.

[0073] The fifth object of the present invention is achieved through the following technical solutions:

[0074] A flame retardant epoxy resin comprises the hydroxyl-containing DOPO composite flame retardant, an epoxy compound and a curing agent.

[0075] Preferably, in the flame-retardant epoxy resin, the mass proportion of the hydroxyl-containing DOPO composite flame retardant is 1 to 30 wt%, and the mass proportion of the epoxy compound and the curing agent is 70 to 99 wt%.

[0076] The weight percentage of the hydroxyl-containing DOPO composite flame retardant is any one of 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, and 30wt%, or a range between any two of them. When the weight percentage is less than 1wt%, the flame retardant performance decreases; when it is greater than 30wt%, the physical properties of the flame retardant epoxy resin decrease.

[0077] The mass ratio of the epoxy compound and the curing agent can be selected to be 80-99 wt %, and further can be selected to be 85-97 wt %.

[0078] The epoxy compound in the flame-retardant epoxy resin contains at least two epoxy groups and is selected from at least one of bisphenol or polyphenol glycidyl ethers (such as bisphenol A epoxy resins E44 and E51), aliphatic chain glycidyl ethers (such as polyethylene glycol diglycidyl ether), aliphatic ring glycidyl ethers (1,3- or 1,4-cyclohexanedimethanol diglycidyl ether), glycidyl esters (such as tetrahydrophthalic acid diglycidyl ester and phthalic acid diglycidyl ester), and heterocyclic epoxy compounds (such as triglycidyl isocyanurate). Preferably, the epoxy compound is selected from commercially available bisphenol glycidyl ethers (such as Baling Petrochemical's E44 and E51).

[0079] Preferably, the curing agent is an amine curing agent, selected from at least one of trimethylenediamine, tetramethylenediamine, hexamethylenediamine, p-phenylenediamine, m-phenylenediamine, p-phenylenediamine, m-phenylenediamine, 4,4-diaminodiphenylmethane, 4,4-diaminodiphenylsulfone, 4,4-diaminodiphenyl ether, dicyandiamide, and 1,4-cyclohexanediamine. Preferably, the curing agent is selected from at least one of trimethylenediamine, tetramethylenediamine, hexamethylenediamine, 4,4-diaminodiphenylmethane, and 4,4-diaminodiphenylsulfone.

[0080] The preparation method of the flame retardant epoxy resin specifically comprises the following steps:

[0081] The epoxy compound, curing agent, and hydroxyl-containing DOPO composite flame retardant are melt-stirred at room temperature to 120°C for 0.1 to 4 hours, cured at 70 to 90°C, 110 to 130°C, and 160 to 180°C for 0.5 to 8 hours, respectively, and naturally cooled to obtain a flame-retardant epoxy resin. Preferably, the melt-stirring time is 0.5 to 2 hours, and the curing time at different temperatures is 0.5 to 4 hours.

[0082] Component A, having the structure of formula (I), is a diol flame retardant containing an aliphatic cyclic bridge chain with an α-hydroxyl group. Compared to DOPO derivatives without hydroxyl groups, this flame retardant can significantly improve compatibility with epoxy resins and reduce the loss of physical properties of epoxy compounds due to the introduction of low-molecular-weight flame retardants. Due to the presence of a rigid cyclic bridge chain, the α-hydroxyl group is chemically more stable and less susceptible to dehydration. Compounds with hydroxyl groups other than those in the α-position or α-hydroxyl groups without a cyclic bridge chain have poorer chemical and thermal stability. Therefore, the former effectively overcomes the shortcomings of the latter, which are prone to thermal degradation or participation in unnecessary chemical reactions.

[0083] The component B having the structure of formula (II) not only contains an α-hydroxyl group and has the advantages of the structure of formula (I), but also contains a ketone group, which can react with the hydroxyl group of the epoxy resin or the amine curing agent, thereby participating in the curing process of the epoxy resin. Therefore, the product having the structure of formula (II) as a reactive curing agent can overcome the adverse effects of the added flame retardant on the physical properties of the epoxy resin, especially the glass transition temperature, and better maintain the original physical properties of the epoxy resin.

[0084] The sixth object of the present invention is achieved through the following technical solutions:

[0085] A low-dielectric flame-retardant resin composition comprises 5 to 150 parts by weight of a hydroxyl-containing DOPO composite flame retardant and 100 parts by weight of a vinyl polyphenylene ether resin.

[0086] The low-dielectric flame-retardant resin composition of the present invention further comprises a crosslinking agent and an initiator. Optionally, 1-200 parts by weight of the crosslinking agent and 0.1-15 parts by weight of the initiator are added to every 100 parts by weight of the vinyl polyphenylene ether resin.

[0087] Preferably, the dielectric loss factor of the low-dielectric flame-retardant resin composition is lower than the dielectric loss factor of a composition comprising the vinyl polyphenylene ether resin but not comprising the hydroxyl-containing DOPO-based composite flame retardant.

[0088] Preferably, the dielectric loss factor of the low-dielectric flame-retardant resin composition is lower than the dielectric loss factor of a composition comprising the vinyl polyphenylene ether resin, a crosslinking agent and an initiator but excluding the hydroxyl-containing DOPO-based composite flame retardant.

[0089] It is known that compounds containing hydroxyl groups have a negative impact on the dielectric loss factor, meaning that the introduction of hydroxyl groups increases the dielectric loss factor. Surprisingly, although component A or mixture C also contains hydroxyl groups, their introduction has a significantly smaller impact on the dielectric loss factor than that of traditional hydroxyl groups. This is because the α-hydroxyl group in component A can form an intramolecular hydrogen bond with P=O. Furthermore, the presence of the cyclic bridge restricts the conformation of the α-hydroxyl group, making the strength of this intramolecular hydrogen bond stronger than that formed by the hydroxyl group on the non-cyclic group. Consequently, the impact of this hydroxyl group on the dielectric loss factor is significantly reduced. Furthermore, this intramolecular hydrogen bond also significantly reduces the chemical activity of the hydroxyl group.

[0090] In the low-dielectric flame-retardant resin composition, 5 to 150 parts by weight of the hydroxyl-containing DOPO composite flame retardant is added per 100 parts by weight of vinyl polyphenylene ether resin. Too little of the hydroxyl-containing DOPO composite flame retardant may result in insufficient flame retardancy; too much may adversely affect the mechanical properties of the flame-retardant resin composition. Alternatively, the amount of the hydroxyl-containing DOPO composite flame retardant can be any one of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, or 150 parts by weight per 100 parts by weight of vinyl polyphenylene ether resin, or a range between any two of these values.

[0091] Preferably, in component A of the hydroxyl-containing DOPO composite flame retardant having the structure of formula (I), R1 and R2 are ethylene, R3=R4=H, and x=y=0. In component B of the hydroxyl-containing DOPO composite flame retardant having the structure of formula (II), R1 and R2 are ethylene, R3=R4=H, and x=y=0.

[0092] The vinyl polyphenylene ether resin refers to a polyphenylene ether resin having an unsaturated double bond in the end-capping group. Optionally, the vinyl polyphenylene ether resin is selected from at least one of Mitsubishi Gas's OPE-2st and SABIC's SA-9000.

[0093] In the described low dielectric constant flame retardant resin composition, comprise crosslinking agent.Alternatively, the consumption of crosslinking agent is the usage amount of 1-200 weight parts of per 100 weight parts of vinyl polyphenylene ether resin.Alternatively, crosslinking agent includes but is not limited to olefin compound, alternatively, crosslinking agent is selected from polybutadiene, polyisoprene, triallyl isocyanurate, triallyl cyanurate, styrene-butadiene-styrene polymer, styrene-butadiene polymer, bismaleimide.Preferably, crosslinking agent is selected from triallyl isocyanurate.

[0094] The low-dielectric flame-retardant resin composition includes an initiator. Optionally, the amount of the initiator is 0.1-15 parts by weight per 100 parts by weight of the vinyl polyphenylene ether resin. Optionally, one or more initiators can be selectively added to promote the curing rate of the resin. Preferably, the initiator comprises a peroxide that can generate free radicals, including but not limited to dicumyl peroxide, di-tert-butyl peroxide dicumyl benzene, tert-butyl perbenzoate, benzoyl peroxide, dibenzoyl peroxide and tert-butyl peroxyisopropyl carbonate. Most preferably, the initiator is dicumyl peroxide.

[0095] Optionally, the low-dielectric flame retardant resin composition includes a polymer resin and / or a functional additive.

[0096] The polymer resin is selected from one or more of thermoplastic polymer resins and thermosetting polymer resins.

[0097] The thermoplastic polymer resin is selected from at least one of polybutadiene, polyamide, polyester, polyphenylene ether, acrylonitrile-butadiene-styrene copolymer, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyimide, polyphenylene sulfide, and polyetheretherketone.

[0098] The thermosetting polymer resin is selected from at least one of epoxy resin, cyanate resin, BT resin, bismaleimide resin, phenolic resin, polyurethane resin, thermosetting polyimide, unsaturated polyester resin, vinyl resin, benzoxazine resin, arylacetylene resin, and furan resin. Preferably, the polymer resin is at least one of epoxy resin, cyanate resin, BT resin, bismaleimide resin, and thermosetting polyimide.

[0099] Optionally, in the low-dielectric flame-retardant resin composition, 1 to 300 parts by weight of the polymer resin are added per 100 parts by weight of the vinyl polyphenylene ether resin. The amount of the polymer resin can be any one of 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 120, 150, 180, 200, 230, 260, and 300 parts by weight, or a range between any two of these values.

[0100] The functional additive can be selected from at least one of a reinforcing agent, an anti-dripping agent, a stabilizer, a pigment, a dye, a carbon-forming catalyst, a dispersant, a nucleating agent, an inorganic filler, an organic filler, and an antioxidant.

[0101] The reinforcing agent may be exemplified by glass fiber.

[0102] The anti-dripping agent may be a polytetrafluoroethylene-based anti-dripping agent.

[0103] Preferably, the inorganic filler is selected from at least one of silicon dioxide, mica, calcium carbonate, aluminum oxide, aluminum nitride, talc, calcium oxide, calcium silicate, glass fiber powder, and silica. Preferably, the inorganic filler is silicon dioxide. Further preferably, the median particle size D of the silicon dioxide is 50 1~15μm.

[0104] Preferably, the organic filler is selected from at least one of polytetrafluoroethylene powder, polyphenylene sulfide powder and polyethersulfone powder.

[0105] Optionally, in the low-dielectric flame-retardant resin composition, 1 to 500 parts by weight of the functional additive are added per 100 parts by weight of vinyl polyphenylene ether resin. The amount of the functional additive can be any one of 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 120, 150, 180, 200, 230, 260, 300, 350, 400, 450, or 500 parts by weight, or a range between any two of the values.

[0106] Optionally, the low-dielectric flame-retardant resin composition further comprises a flame retardant Q, and the flame retardant Q is selected from at least one of a phosphorus-based flame retardant, a nitrogen-based flame retardant, and a boron-based flame retardant.

[0107] Preferably, the phosphorus-based flame retardant is at least one selected from bisphosphate flame retardants, phosphazene flame retardants, dialkyl phosphinates, DOPO derivatives, and phosphine oxide compounds.

[0108] Furthermore, the bisphosphate flame retardant is selected from at least one of bisphenol A bisdiphenyl phosphate, resorcinol bisdiphenyl phosphate, and 1,3-phenylene (2,6-xylyl) tetraphosphate.

[0109] Furthermore, the phosphazene flame retardant is selected from at least one of hexaphenoxycyclotriphosphazene, cyanophenoxyphosphazene (such as FP-300 of Fushimi Pharmaceutical Co., Ltd. of Japan), allyl cyclophosphazene (such as SPV-100 of Otsuka of Japan), and cyclic biphenyloxyphosphazene (such as BP-PZ of Otsuka of Japan).

[0110] Furthermore, the dialkyl phosphinate is at least one selected from the group consisting of aluminum diethylphosphinate, aluminum diisobutylphosphinate, aluminum dipropylphosphinate, and zinc diethylphosphinate.

[0111] Furthermore, the DOPO derivative is selected from at least one of 6H-dibenzo[c,e][1,2]oxophosphoglycerate, 6,6'-(1,2-ethanediyl)bis-6,6'-dioxide, 6H-dibenzo[c,e][1,2]oxane-6,6'-(1,4-ethanediyl)bis-,6,6'-dioxide, and 6H-dibenzo[c,e][1,2]oxane-6,6'-(1,4-phenylethanediyl)bis-6,6'-dioxide (such as HTP-6123 of Guizhou Yuanyi Group).

[0112] Furthermore, the phosphine oxide compound is p-xylylbisdiphenylphosphine oxide (such as PQ-60 from Jinyi Chemical).

[0113] Preferably, the nitrogen-based flame retardant is selected from at least one of melamine cyanurate, melamine polyphosphate, and ammonium polyphosphate;

[0114] Preferably, the boron-based flame retardant is selected from zinc borate.

[0115] Optionally, in the low-dielectric flame-retardant resin composition, 1 to 30 parts by weight of the flame retardant Q are added per 100 parts by weight of vinyl polyphenylene ether resin. The amount of the flame retardant Q can be any one of 1, 2, 3, 4, 5, 8, 10, 12, 15, 18, 20, 25, and 30 parts by weight, or a range between any two of these values.

[0116] Compared with the prior art, the present invention has the following beneficial effects:

[0117] 1. By controlling the reaction time, reaction molar ratio, reaction temperature and other process conditions, as well as through subsequent purification steps, component A having a structure of formula (I) and component B having a structure of formula (II) can be effectively obtained. Physical mixing of component A and component B can obtain the hydroxyl-containing DOPO composite flame retardant of the present invention;

[0118] 2. By controlling process conditions such as reaction time, reaction molar ratio, reaction temperature, and subsequent purification steps, a mixed product of component A having a structure of formula (I) and component B having a structure of formula (II) can be effectively obtained, namely the hydroxyl-containing DOPO-based composite flame retardant of the present invention. Compared with obtaining component A, the preparation process of this mixed product does not require the removal of component B, resulting in a shorter reaction time, simpler purification, and better economic efficiency.

[0119] 3. The hydroxyl-containing DOPO composite flame retardant of the present invention can significantly reduce the dielectric loss factor (Df) of polymer materials despite containing hydroxyl groups, which is completely unexpected;

[0120] 4. The mixture C composed of component A and component B achieves a combination of high flame retardancy and high physical properties for the flame retardant material, overcoming the shortcomings of low flame retardancy efficiency of component B alone and decreased mechanical properties of polymer materials caused by using component A alone. BRIEF DESCRIPTION OF THE DRAWINGS

[0121] FIG1 is a nuclear magnetic phosphorus spectrum of the product of Example 1 of the present invention;

[0122] FIG2 is a hydrogen NMR spectrum of the product of Example 1 of the present invention;

[0123] FIG3 is an infrared spectrum of the product of Example 1 of the present invention;

[0124] FIG4 is a nuclear magnetic phosphorus spectrum of the product of Example 2 of the present invention;

[0125] FIG5 is a hydrogen NMR spectrum of the product of Example 2 of the present invention;

[0126] FIG6 is an infrared spectrum of the product of Example 2 of the present invention;

[0127] FIG7 is a nuclear magnetic phosphorus spectrum of the product of Example 6 of the present invention;

[0128] FIG8 is a hydrogen NMR spectrum of the product of Example 6 of the present invention;

[0129] FIG9 is an infrared spectrum of the product of Example 6 of the present invention. DETAILED DESCRIPTION

[0130] Below by specific embodiment and accompanying drawing, technical scheme of the present invention is further described explanation, it should be understood that specific embodiment described herein is only for helping to understand the present invention, is not used for specific limitation of the present invention.And accompanying drawing used herein, is only for better illustrating the disclosure of the present invention, does not have limiting effect on protection scope.If no special instructions, the raw materials adopted in the embodiment of the present invention are all raw materials commonly used in this area, and the method adopted in the embodiment is all conventional method in this area.

[0131] The chemical reagents used in the following examples and comparative examples are as follows:

[0132] (A1) E44 bisphenol A epoxy resin, purchased from Baling Petrochemical, epoxy value 0.44;

[0133] (B1) 4,4-Diaminodiphenylmethane (DDM), a curing agent, purchased from Aladdin Reagent;

[0134] (C1) vinyl polyphenylene ether resin, manufactured by Sabic Corporation, trade name SA9000;

[0135] (D) Triallyl isocyanurate (TAIC), a cross-linking agent, purchased from Aladdin Reagents;

[0136] (E1) Flame retardant component A prepared in Example 6.

[0137] (E2) Flame retardant component B prepared in Example 1.

[0138] (E3) Flame retardant mixture C prepared from Example 3.

[0139] (E4) Flame retardant mixture C prepared from Example 5.

[0140] (E5) Vinylene-bridged DiDOPO-A was prepared according to Chinese patent application CN110885344 A. The specific preparation method is as follows: 32.4 g DOPO (0.15 mol), 25 g diphenylmethane, and 20 g xylene were added to a four-necked flask equipped with a thermometer, a water separator, a mechanical stirrer, and a constant pressure funnel. Under nitrogen, the mixture was heated to 195°C. A mixed solution of 6.6 g ethylene carbonate (0.075 mol) and 0.34 g sodium iodide (0.0023 mol) was then added dropwise at a constant rate over 2.5 hours. The reaction was then incubated at 195°C for 2 hours to complete. After cooling, 38 g isopropyl alcohol was added, and the mixture was stirred under reflux for 20 minutes. After cooling, the mixture was filtered. The solid product was washed with isopropyl alcohol and then three times with an appropriate amount of deionized water. The mixture was then dried in vacuo at 180°C to obtain a white solid powder, namely, vinylene-bridged DiDOPO-A.

[0141] (E6) Product of DOPO and formaldehyde; Preparation method: 43.20 g DOPO (0.20 mol) and 60 g xylene were added to a four-necked flask equipped with a thermometer, magnetic stirring, and reflux. Under nitrogen, the mixture was heated to 95°C. 6.01 g paraformaldehyde (0.20 mol) was then added in multiple portions. The reaction was then continued at 95°C for 4 hours. After cooling, the mixture was filtered, the solid product was washed with toluene, and vacuum dried at 100°C to obtain a white solid powder, which is the addition product of DOPO and formaldehyde.

[0142] (E7) Product of DOPO and acetone; Preparation method: 21.60 g DOPO (0.10 mol) and 46.4 g acetone (0.40 mol) were added to a four-necked flask equipped with a thermometer, magnetic stirring, and reflux. Under nitrogen, the mixture was heated to reflux temperature and then refluxed for 4 hours to complete the reaction. After cooling, the mixture was filtered and the solid product was washed with acetone and then three times with an appropriate amount of deionized water. The product was then dried in vacuo at 80°C to obtain a white solid powder, which is the addition product of DOPO and acetone.

[0143] (F1) polybutadiene (PB), purchased from MacLean's reagent;

[0144] (F2) BT resin, obtained by curing N,N'-4,4'-diphenylmethane bismaleimide (BMI) and cyanate ester resin (CE), both purchased from Aladdin reagents;

[0145] (G) Dicumyl peroxide (DCP), initiator, purchased from Aladdin Reagent;

[0146] (H) Spherical silica, an inorganic filler, purchased from Qinghe County Andy Metal Materials Co., Ltd., with a particle size of 2 μm;

[0147] (I) 1,4-cyclohexanedione, purchased from Aladdin Reagent;

[0148] (J) 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was purchased from MacLean's reagent.

[0149] The characterization methods in the embodiments and comparative examples are as follows:

[0150] (1) Nuclear magnetic resonance spectroscopy (NMR): performed on a Bruker AVANCE III 400M NMR spectrometer (Bruker, USA) using deuterated dimethyl sulfoxide as the solvent.

[0151] (2) Fourier transform infrared spectroscopy (FTIR): performed on a Nicolet 6700 infrared spectrometer (Thermo-Fisher, USA) using the KBr method.

[0152] The performance testing methods of the flame retardant resin materials prepared in the examples and comparative examples are as follows:

[0153] (1) Flame retardant test: UL-94 vertical combustion test was carried out on a 5400 horizontal / vertical combustion apparatus according to ASTM D3801.

[0154] [Corrected 14.08.2023 according to Rule 26] (2) Mechanical property test: Tensile and bending tests were carried out on a 5567 universal tensile tester (Instron, USA) in accordance with GB / T 1040.1-2006 and GB / T 9341-2000 standards, respectively; notched impact tests were carried out on a GT-7045-HML impact tester (GOTECH, Taiwan, China) in accordance with ISO179-1:98.

[0155] (3) Glass transition temperature (T g ): T of the polyphenylene ether resin composition g The T values ​​of epoxy resin materials were obtained by TMA 402 F3 thermomechanical analyzer (NETZSCH, Germany). g The measurements were carried out on DSC (METTLER, Sweden).

[0156] (4) Dielectric constant (Dk) and dielectric loss factor (Df): The dielectric constant (Dk) and dielectric loss factor (Df) of the flame retardant resin material were measured on a ZNA Vector Network Analyzer (ROHDE & SCHWARZ, Germany) using the stripline method. Df was taken as the average value of 9-12 GHz.

[0157] (5) Coefficient of thermal expansion (CTE): Thermomechanical analysis (TMA) was used to test the CTE on a TMA 402 F3 thermomechanical analyzer (NETZSCH, Germany).

[0158] Example 1

[0159] Under nitrogen, 0.05 mol of 1,4-cyclohexanedione was placed in a 250 mL four-necked round-bottom flask equipped with a thermometer, reflux, and magnetic stirring. 100 mL of p-xylene was added and the mixture was heated to 120°C until completely dissolved. 0.050 mol of DOPO was then added in two batches. The reaction was continued at 120°C for 2 hours. After the reaction, the mixture was filtered while hot and washed three times with hot toluene. The washed solid product was vacuum-dried at 100°C to yield a white product, component B, having the structure of formula (II). In the formula, R1 and R2 are ethylene (-CH2CH2-), R3 and R4 are hydrogen, and x=y=0. The yield was 94.8%.

[0160] The NMR phosphorus spectrum of component B prepared in Example 1 is shown in Figure 1, and the NMR hydrogen spectrum is shown in Figure 2. NMR: 31 PNMR, 35 ppm; 1 HNMR, 7-8.5ppm is benzene ring hydrogen, 5.90ppm is hydroxyl hydrogen, 2.0-2.7ppm is aliphatic ring hydrogen. Its infrared spectrum is shown in Figure 3, carbonyl peak (1708cm -1) and hydroxyl peak (3263 cm -1 ).

[0161] Example 2

[0162] Under nitrogen, 0.10 mol of DOPO was placed in a 250 mL four-necked round-bottom flask equipped with a thermometer, reflux, and magnetic stirring. 120 mL of p-xylene was added and the mixture was heated to 120°C for complete dissolution. 0.05 mol of 1,4-cyclohexanedione was added in two portions and the reaction continued at 120°C for 2 hours. After the reaction, the mixture was filtered while hot, washed three times with hot toluene, and dried under vacuum at 100°C to obtain a white mixed product. The theoretical yield, assuming the complete formation of the diaddition product, Component A, was 84.0%. Nuclear magnetic resonance analysis and calculation of the unreacted DOPO mass revealed that the mixed product contained 73 wt% Component A of formula (I) and 27 wt% Component B of formula (II), where R1 and R2 are ethylene (-CH2CH2-), R3 and R4 are hydrogen, and x=y=0.

[0163] The NMR phosphorus spectrum of the mixed product prepared in Example 2 is shown in Figure 4, and the NMR hydrogen spectrum is shown in Figure 5. NMR: 31 PNMR, 36 ppm is the double addition product component A, 35 ppm is the single addition product component B; 1 HNMR, 7-8.5ppm is benzene ring hydrogen, 5.90ppm is hydroxyl hydrogen on component B, 5.42ppm and 5.43ppm are hydroxyl hydrogen on component A, 2.0-2.7ppm is aliphatic ring hydrogen. Its infrared spectrum is shown in Figure 6, infrared spectrum: carbonyl peak (1708cm -1 ) and hydroxyl peak (3263 cm -1 ).

[0164] Example 3

[0165] Under nitrogen, 0.10 mol of DOPO was placed in a 250 mL four-necked round-bottom flask equipped with a thermometer, reflux, and magnetic stirring. 120 mL of p-xylene was added and the mixture was heated to 120°C for complete dissolution. 0.05 mol of 1,4-cyclohexanedione was added in two portions and the reaction continued at 120°C for 2 hours. After the reaction, the mixture was filtered while hot, washed three times with hot isopropanol, and dried under vacuum at 100°C to obtain a white mixed product. The theoretical yield, assuming complete formation of the diaddition product, component A, was 84.6%. Nuclear magnetic resonance analysis and calculation of the unreacted DOPO mass revealed that the mixed product contained 82 wt% component A of formula (I) and 18 wt% component B of formula (II), where R1 and R2 are ethylene (-CH2CH2-), R3 and R4 are hydrogen, and x=y=0.

[0166] Example 4

[0167] Under nitrogen, 0.15 mol of DOPO was placed in a 250 mL four-necked round-bottom flask equipped with a thermometer, reflux, and magnetic stirring. 120 mL of p-xylene was added and the mixture was heated to 120°C for complete dissolution. 0.05 mol of 1,4-cyclohexanedione was added in two portions and the reaction continued at 120°C for 2 hours. After the reaction, the mixture was filtered while hot, washed three times with hot toluene, and dried under vacuum at 100°C to obtain a white mixed product. The theoretical yield, assuming the complete formation of the diaddition product, Component A, was 96.3%. Nuclear magnetic resonance analysis and calculation of the unreacted DOPO mass revealed that the mixed product contained 94 wt% Component A of formula (I) and 6 wt% Component B of formula (II), where R1 and R2 are ethylene (-CH2CH2-), R3 and R4 are hydrogen, and x=y=0.

[0168] Example 5

[0169] Under nitrogen, 0.15 mol of DOPO was placed in a 250 mL four-necked round-bottom flask equipped with a thermometer, reflux, and magnetic stirring. 120 mL of p-xylene was added and the mixture was heated to 120°C until completely dissolved. 0.05 mol of 1,4-cyclohexanedione was added in two portions, and the reaction continued at 120°C for 2 hours. After the reaction, the mixture was filtered while hot, washed three times with hot isopropanol, and dried under vacuum at 100°C to obtain a white mixed product. The theoretical yield, assuming complete formation of the diaddition product, component A, was 99.0%. Nuclear magnetic resonance analysis and calculation of the unreacted DOPO mass revealed that the mixed product contained 98 wt% component A of formula (I) and 2 wt% component B of formula (II), where R1 and R2 are ethylene (-CH2CH2-), R3 and R4 are hydrogen, and x=y=0.

[0170] Example 6

[0171] Under nitrogen, 0.15 mol of DOPO was placed in a 250 mL four-necked round-bottom flask equipped with a thermometer, reflux, and magnetic stirring. 120 mL of p-xylene was added and the mixture was heated to 120°C until completely dissolved. 0.05 mol of 1,4-cyclohexanedione was added in two portions, and the reaction was continued at 120°C for 5 hours. After the reaction, the mixture was filtered while hot and washed five times with hot isopropanol. The washed solid product was vacuum-dried at 100°C to obtain a white product for future use (yield: 99.0%). Nuclear magnetic resonance analysis confirmed that the white product was component A having the structure of formula (I), where R1 and R2 are ethylene (-CH2CH2-), R3 and R4 are hydrogen, and x=y=0.

[0172] Example 7

[0173] 77.0 parts of bisphenol A epoxy resin E44, 5.7 parts of the product of Example 6, and 0.3 parts of the product of Example 1 were weighed and mixed uniformly at 90° C. with magnetic stirring. 17.0 parts of DDM were weighed and added thereto. The mixture was completely melted at 90° C., degassed in a vacuum oven at 80° C. for 3 min, and quickly poured into a preheated mold. The mixture was allowed to stand for 5 min, heated to 120° C. and cured for 2 h, then heated to 170° C. and cured for 4 h. Finally, the mixture was naturally cooled to room temperature to obtain specimens for UL-94 vertical burning, tensile, bending, and notched impact tests. The results are shown in Table 1.

[0174] Example 8

[0175] 77.0 parts of epoxy bisphenol A resin E44, 5.4 parts of the product of Example 6, and 0.6 parts of the product of Example 1 were weighed and mixed uniformly at 90°C with magnetic stirring. 17.0 parts of DDM were weighed and added thereto. The mixture was completely melted at 90°C, degassed in a vacuum oven at 80°C for 3 minutes, and quickly poured into a preheated mold. The mixture was allowed to stand for 5 minutes, heated to 120°C and cured for 2 hours, then heated to 170°C and cured for 4 hours. Finally, the mixture was naturally cooled to room temperature to obtain specimens for UL-94 vertical burning, LOI, tensile, bending, and notched impact tests. The results are shown in Table 1.

[0176] Example 9

[0177] 74.5 parts of epoxy bisphenol A resin E44, 4.8 parts of the product of Example 6, and 3.2 parts of the product of Example 1 were weighed and mixed uniformly at 90° C. with magnetic stirring. 17.5 parts of DDM were weighed and added thereto. The mixture was completely melted at 90° C., degassed in a vacuum oven at 80° C. for 3 min, and quickly poured into a preheated mold. The mixture was allowed to stand for 5 min, heated to 120° C. and cured for 2 h, then heated to 170° C. and cured for 4 h. Finally, the mixture was naturally cooled to room temperature to obtain specimens for UL-94 vertical burning, limiting oxygen index (LOI), tensile, bending, and notched impact tests. The results are shown in Table 1.

[0178] Example 10

[0179] 74.5 parts of epoxy bisphenol A resin E44, 4.0 parts of the product of Example 6, and 4.0 parts of the product of Example 1 were weighed and mixed uniformly at 90° C. with magnetic stirring. 17.5 parts of DDM were weighed and added thereto. The mixture was completely melted at 90° C., degassed in a vacuum oven at 80° C. for 3 min, and quickly poured into a preheated mold. The mixture was allowed to stand for 5 min, heated to 120° C. and cured for 2 h, then heated to 170° C. and cured for 4 h. Finally, the mixture was naturally cooled to room temperature to obtain specimens for UL-94 vertical burning, limiting oxygen index (LOI), tensile, bending, and notched impact tests. The results are shown in Table 1.

[0180] Example 11

[0181] 74.5 parts of epoxy bisphenol A resin E44 and 8.0 parts of the product of Example 3 were weighed and mixed uniformly at 90°C with magnetic stirring. 17.5 parts of DDM were weighed and added thereto. The mixture was completely melted at 90°C and degassed in a vacuum oven at 80°C for 3 minutes. The mixture was quickly poured into a preheated mold and allowed to stand for 5 minutes. The mixture was then heated to 120°C and cured for 2 hours. The mixture was then heated to 170°C and cured for 4 hours. The mixture was then naturally cooled to room temperature to obtain specimens for UL-94 vertical burning, limiting oxygen index (LOI), tensile, bending, and notched impact tests. The results are shown in Table 1.

[0182] Example 12

[0183] 100 parts SA9000, 50 parts TAIC, and 200 parts toluene were weighed and completely dissolved under magnetic stirring at room temperature. 50 parts of the flame retardant prepared in Example 5 were added, the mixture was heated to 70°C and stirred until uniformly free of bubbles. 4 parts DCP were added and stirred at 70°C for 30 minutes. The mixture was then transferred to an 80°C vacuum oven to remove the toluene, yielding a precured resin. The desolventized precured resin was placed in a mold preheated at 100°C and cured in a flat-bed vulcanizer using the following curing schedule: 1 hour at 150°C, 2 hours at 170°C, 1 hour at 190°C, and 1 hour at 220°C. The mixture was then cooled naturally to room temperature to yield samples for UL-94 vertical combustion, dielectric properties, and thermal expansion coefficient testing. The results are shown in Table 2.

[0184] Example 13

[0185] 100 parts SA9000, 50 parts TAIC, and 200 parts toluene were weighed and completely dissolved under magnetic stirring at room temperature. 50 parts of the flame retardant prepared in Example 3 were added, the mixture was heated to 70°C and stirred until no bubbles were present. 4 parts DCP were added and stirred at 70°C for 30 minutes. The mixture was then transferred to an 80°C vacuum oven to remove the toluene and obtain a precured resin. The solvent-free precured resin was placed in a mold preheated at 100°C and cured in a flat-plate vulcanizer using the following curing schedule: 1 hour at 150°C, 2 hours at 170°C, 1 hour at 190°C, and 1 hour at 220°C. The mixture was then cooled naturally to room temperature to obtain samples for UL-94 vertical combustion, dielectric properties, and thermal expansion coefficient testing. The results are shown in Table 2.

[0186] Example 14

[0187] 100 parts SA9000, 50 parts TAIC, 72 parts PB, and 200 parts toluene were weighed and completely dissolved under magnetic stirring at room temperature. 80 parts silica and 112 parts flame retardant prepared in Example 5 were added, respectively. The mixture was heated to 70°C and stirred until no bubbles were present. 4 parts DCP was added and stirred at 70°C for 30 minutes. The mixture was then transferred to an 80°C vacuum oven to remove the toluene and obtain a precured resin. The solvent-free precured resin was placed in a mold preheated at 100°C and cured in a flatbed vulcanizer at the following curing schedule: 1 hour at 150°C, 2 hours at 170°C, 1 hour at 190°C, and 1 hour at 220°C. The mixture was then cooled naturally to room temperature. Samples for UL-94 vertical burning, dielectric properties, and thermal expansion coefficient testing were obtained. The results are shown in Table 2.

[0188] Example 15

[0189] 100 parts SA9000, 50 parts TAIC, 57.6 parts CE, 14.4 parts BMI, and 200 parts toluene were weighed and magnetically stirred at room temperature. 80 parts silica and 112 parts of Mixture C prepared in Example 5 were added, respectively. The mixture was heated to 70°C and stirred until no bubbles were present. 4 parts DCP was added and stirred at 70°C for 30 minutes. The mixture was then transferred to an 80°C vacuum oven to remove the toluene, yielding a precured resin. The desolventized precured resin was placed in a mold preheated at 100°C and cured in a flatbed vulcanizer at the following curing schedule: 150°C for 1 hour, 170°C for 2 hours, 190°C for 1 hour, and 220°C for 1 hour. The mixture was then cooled naturally to room temperature. Samples were obtained for UL-94 vertical burning, dielectric properties, and thermal expansion coefficient testing. The results are shown in Table 2.

[0190] Example 16

[0191] Under nitrogen protection, 5.44 g of the product obtained in Example 6 (0.01 mol) and 10.20 g of acetic anhydride (0.10 mol) were placed in a 100 mL four-necked round-bottom flask equipped with a thermometer, reflux condenser and magnetic stirring. The temperature was raised to 140°C and refluxed for 6 h. After the white turbid liquid was naturally cooled, it was filtered and the precipitate was washed three times with anhydrous ethanol and dried in a vacuum oven at 80°C. After infrared testing, the result was completely consistent with the product obtained in Example 6, indicating that the hydroxyl group of component A has strong chemical stability, does not degrade, and does not react with acetic anhydride.

[0192] Example 17

[0193] Under nitrogen protection, 5.44 g of the product obtained in Example 6 (0.01 mol), 15.01 g of isopropyl acetate (0.15 mol) and 5% p-toluenesulfonic acid were placed in a 100 mL four-necked round-bottom flask equipped with a thermometer, reflux and magnetic stirring. The temperature was raised to 95° C. and refluxed for 4 h. After the white turbid liquid was naturally cooled, it was filtered and the precipitate was washed three times with anhydrous ethanol and dried in a vacuum oven at 80° C. After infrared testing, the result was completely consistent with the product obtained in Example 6, indicating that the hydroxyl group of component A has strong chemical stability, does not degrade, and does not react with isopropyl acetate.

[0194] Comparative Example 1

[0195] Under nitrogen protection, 2.74g of the addition product of DOPO and acetone (0.01mol) and 10.20g of acetic anhydride (0.10mol) were placed in a 100mL four-necked round-bottom flask equipped with a thermometer, reflux and magnetic stirring. The temperature was raised to 140℃ and refluxed for 1h to obtain a clear and transparent liquid. After natural cooling, the excess acetic anhydride was removed by vacuum distillation to obtain a yellow viscous liquid. Infrared spectroscopy showed a clear carbonyl peak (1771cm -1 and 1747cm -1 ), indicating that the hydroxyl group of the addition product of DOPO and acetone is highly active and reacts with acetic anhydride; the phosphorus spectrum of nuclear magnetic resonance testing shows that the addition product of DOPO and acetone will undergo esterification reaction, dehydration reaction and reverse reaction of deacetone to regenerate DOPO, with the three types of reactions accounting for 18%, 37% and 45% respectively.

[0196] Comparative Example 2

[0197] Under nitrogen protection, 246g of the addition product of DOPO and formaldehyde (0.01mol) and 10.20g of acetic anhydride (0.10mol) were placed in a 100mL four-necked round-bottom flask equipped with a thermometer, reflux and magnetic stirring. The temperature was raised to 140℃ and refluxed for 3h to obtain a clear and transparent liquid. After natural cooling, the excess acetic anhydride was removed by vacuum distillation to obtain a yellow viscous liquid. Infrared spectroscopy showed a clear carbonyl peak (1753cm -1 ), indicating that the hydroxyl group of the addition product of DOPO and formaldehyde is highly active and reacts with acetic anhydride; NMR tests show that the acetylated addition product of DOPO and formaldehyde 31 PNMR: 28ppm.

[0198] It can be concluded from Examples 16 and 17 and Comparative Examples 1 and 2 that the hydroxyl groups of the flame retardant prepared in Example 6 are chemically inert, while the hydroxyl groups of the adducts of DOPO and formaldehyde or acetone, which have similar structures but non-cyclic bridge structures, are highly chemically active. The adducts of DOPO and acetone can even degrade and revert to DOPO and acetone under heating.

[0199] Comparative Example 3

[0200] 82.1 parts of bisphenol A epoxy resin E44 were weighed and mixed uniformly at 90°C with magnetic stirring. 17.9 parts of DDM were weighed and added to the mixture. The mixture was completely melted at 90°C and degassed in a vacuum oven at 80°C for 3 minutes. The mixture was quickly poured into a preheated mold and allowed to stand for 5 minutes. The mixture was then heated to 120°C and cured for 2 hours. The mixture was then heated to 170°C and cured for 4 hours. The mixture was then naturally cooled to room temperature to obtain specimens for UL-94 vertical burning, tensile, bending, and notched impact tests. The results are shown in Table 1.

[0201] Comparative Example 4

[0202] 77.0 parts of bisphenol A epoxy resin E44 and 6.0 parts of DiDOPO-A were weighed and mixed uniformly at 90°C with magnetic stirring. 17.0 parts of DDM was weighed and added, and the mixture was completely melted at 90°C. The mixture was degassed in a vacuum oven at 80°C for 3 minutes and quickly poured into a preheated mold. The mixture was allowed to stand for 5 minutes, then heated to 120°C and cured for 2 hours. The temperature was then raised to 170°C and cured for 4 hours. Finally, the mixture was naturally cooled to room temperature to obtain specimens for UL-94 vertical burning, tensile, bending, and notched impact tests. The results are shown in Table 1.

[0203] Comparative Example 5

[0204] 77.0 parts of epoxy bisphenol A resin E44 and 6.0 parts of the product of Example 6 were weighed and mixed uniformly at 90°C with magnetic stirring. 17.0 parts of DDM were weighed and added thereto. The mixture was completely melted at 90°C and degassed in a vacuum oven at 80°C for 3 minutes. The mixture was quickly poured into a preheated mold and allowed to stand for 5 minutes. The mixture was heated to 120°C and cured for 2 hours. The temperature was then raised to 170°C and cured for 4 hours. Finally, the mixture was naturally cooled to room temperature to obtain specimens for UL-94 vertical burning, tensile, bending, and notched impact tests. The results are shown in Table 1.

[0205] Comparative Example 6

[0206] 77.0 parts of epoxy bisphenol A resin E44 and 6.0 parts of the product of Example 1 were weighed and mixed uniformly at 90° C. with magnetic stirring. 17.0 parts of DDM were weighed and added thereto. The mixture was completely melted at 90° C. and degassed in a vacuum oven at 80° C. for 3 min. The mixture was quickly poured into a preheated mold and allowed to stand for 5 min. The mixture was heated to 120° C. and cured for 2 h. The temperature was then raised to 170° C. and cured for 4 h. The mixture was then naturally cooled to room temperature to obtain specimens for UL-94 vertical burning, limiting oxygen index (LOI), tensile, bending, and notched impact tests. The results are shown in Table 1.

[0207] Comparative Example 7

[0208] Weigh 100 parts of SA9000, 50 parts of TAIC, and 200 parts of toluene and completely dissolve them under magnetic stirring at room temperature. Heat the mixture to 70°C, add 4 parts of DCP, and stir at 70°C for 30 minutes. The mixture is then transferred to an 80°C vacuum oven to remove the toluene, yielding a precured resin. The desolventized precured resin is placed in a mold preheated at 100°C and cured in a flat-bed vulcanizer using the following curing schedule: 1 hour at 150°C, 2 hours at 170°C, 1 hour at 190°C, and 1 hour at 220°C. The resin is then cooled naturally to room temperature to yield samples for UL-94 vertical burning, dielectric properties, and thermal expansion coefficient testing. The results are shown in Table 2.

[0209] Comparative Example 8

[0210] 100 parts SA9000, 50 parts TAIC, and 200 parts toluene were weighed and completely dissolved under magnetic stirring at room temperature. 50 parts DiDOPO-A was added, heated to 70°C, and stirred until no bubbles were present. 4 parts DCP was added and stirred at 70°C for 30 minutes. The mixture was then transferred to an 80°C vacuum oven to remove the toluene, yielding a precured resin. The solvent-free precured resin was placed in a mold preheated at 100°C and cured in a flat-bed vulcanizer at 150°C for 1 hour, 170°C for 2 hours, 190°C for 1 hour, and 220°C for 1 hour. The resin was then cooled naturally to room temperature. This yielded samples for UL-94 vertical burning, dielectric properties, and thermal expansion coefficient testing. The results are shown in Table 2.

[0211] Comparative Example 9

[0212] 100 parts SA9000, 50 parts TAIC, and 200 parts toluene were weighed and completely dissolved under magnetic stirring at room temperature. 50 parts of the flame retardant prepared in Example 6 were added, the mixture was heated to 70°C and stirred until no bubbles were present. 4 parts DCP were added and stirred at 70°C for 30 minutes. The mixture was then transferred to an 80°C vacuum oven to remove the toluene and obtain a precured resin. The solvent-free precured resin was placed in a mold preheated at 100°C and cured in a flat-bed vulcanizer using the following curing schedule: 1 hour at 150°C, 2 hours at 170°C, 1 hour at 190°C, and 1 hour at 220°C. The mixture was then cooled naturally to room temperature to obtain samples for UL-94 vertical combustion, dielectric properties, and thermal expansion coefficient testing. The results are shown in Table 2.

[0213] Comparative Example 10

[0214] 100 parts SA9000, 50 parts TAIC, and 200 parts toluene were weighed and completely dissolved under magnetic stirring at room temperature. 50 parts of the flame retardant prepared in Example 1 were added, the mixture was heated to 70°C and stirred until no bubbles were present. 4 parts DCP were added and stirred at 70°C for 30 minutes. The mixture was then transferred to an 80°C vacuum oven to remove the toluene and obtain a precured resin. The solvent-free precured resin was placed in a mold preheated at 100°C and cured in a flat-plate vulcanizer using the following curing schedule: 1 hour at 150°C, 2 hours at 170°C, 1 hour at 190°C, and 1 hour at 220°C. The mixture was then cooled naturally to room temperature to obtain samples for UL-94 vertical combustion, dielectric properties, and thermal expansion coefficient testing. The results are shown in Table 2.

[0215] Comparative Example 11

[0216] 100 parts of SA9000, 50 parts of TAIC, and 200 parts of toluene were weighed and completely dissolved under magnetic stirring at room temperature. 50 parts of the addition product of DOPO and formaldehyde were added, heated to 70°C, and stirred until no bubbles were present. 4 parts of DCP were added and stirred at 70°C for 30 minutes. The mixture was then transferred to an 80°C vacuum oven to remove the toluene, yielding a precured resin. The solvent-free precured resin was placed in a mold preheated at 100°C and cured in a flat-bed vulcanizer at the following curing schedule: 150°C for 1 hour, 170°C for 2 hours, 190°C for 1 hour, and 220°C for 1 hour. The mixture was then cooled naturally to room temperature. Samples were obtained for UL-94 vertical burning, dielectric properties, and thermal expansion coefficient testing. The results are shown in Table 2.

[0217] Comparative Example 12

[0218] 100 parts of SA9000, 50 parts of TAIC, and 200 parts of toluene were weighed and completely dissolved under magnetic stirring at room temperature. 50 parts of the addition product of DOPO and acetone were added, heated to 70°C, and stirred until no bubbles were present. 4 parts of DCP were added and stirred at 70°C for 30 minutes. The mixture was then transferred to an 80°C vacuum oven to remove the toluene, yielding a precured resin. The solvent-free precured resin was placed in a mold preheated at 100°C and cured in a flat-bed vulcanizer at the following curing schedule: 150°C for 1 hour, 170°C for 2 hours, 190°C for 1 hour, and 220°C for 1 hour. The mixture was then cooled naturally to room temperature. Samples were obtained for UL-94 vertical burning, dielectric properties, and thermal expansion coefficient testing. The results are shown in Table 2.

[0219] Table 1 Flame retardant epoxy resin material formula and properties

[0220] As can be seen in Table 1, Comparative Example 3 demonstrates that the epoxy resin has excellent mechanical properties, particularly a high glass transition temperature, but is not flame retardant. Comparative Example 4 demonstrates that the addition of DiDOPO-A to the epoxy resin improves flame retardancy, but mechanical properties decrease, particularly a significant decrease in Tg. Comparative Example 5 demonstrates that Component A is superior to DiDOPO-A in maintaining the physical properties, particularly the glass transition temperature, of the flame-retardant epoxy resin. Comparative Examples 6 and 5 demonstrate that the mechanical properties of the epoxy resin flame-retarded using Component B alone are superior to those of the epoxy resin flame-retarded using Component A alone, but the flame retardant performance of the former is inferior to that of the latter. Examples 7-11 demonstrate that Blend C not only has higher efficiency than Component B but also achieves the same flame retardant effect as Component A, indicating that the introduction of Component B does not reduce the flame retardant efficiency of Component C, which is quite surprising. Furthermore, the results of Examples 7-10 demonstrate that the flame-retarded epoxy resin of Blend C has a higher glass transition temperature than the epoxy resin flame-retarded using Components A and B alone, reaching or even exceeding the glass transition temperature of the original epoxy resin, which is completely unexpected.

[0221] Table 2 Low dielectric constant flame retardant polyphenylene ether resin formula

[0222] As shown in Table 2, the vinyl polyphenylene ether resin composition in Comparative Example 7 has a high glass transition temperature and a low Df value, but is not flame retardant. Comparative Example 9 demonstrates that component A can improve the flame retardancy of polyphenylene ether resins, increasing the glass transition temperature, and reducing the Df value and linear thermal expansion coefficient. Comparative Example 10 demonstrates that component B can improve the flame retardancy of polyphenylene ether resins, but at the expense of a lower glass transition temperature and an increase in the Df value and linear thermal expansion coefficient. Comparative Examples 8 and 9 demonstrate that component A maintains higher flame retardancy than DiDOPO-A. The results of Comparative Examples 11 and 12, as well as Comparative Example 7, demonstrate that DOPO derivatives containing hydroxyl groups but lacking cyclic bridge structures not only have poor flame retardancy but also significantly increase the Df value of polyphenylene ether resin systems. Example 12 and Comparative Example 9 demonstrate that mixture C, containing components A and B, can also improve the flame retardancy of polyphenylene ether resins, and that the addition of an appropriate amount of component B does not reduce the flame retardancy of mixture C. Furthermore, the results of Example 12 demonstrate that the introduction of Component C can similarly reduce the Df value and linear thermal expansion coefficient of the polyphenylene ether resin, a performance comparable to that of Component A. Examples 14 and 15 demonstrate that even after introducing thermoplastic polybutadiene and thermosetting BT resin into the polyphenylene ether system, Component C still maintains the resin's excellent flame retardancy, exhibiting low Df value, linear thermal expansion coefficient, and high glass transition temperature. Furthermore, as can be seen from Examples 1, 2, 3, 4, 5, and 6, the preparation of Component A alone results in high raw material consumption, long reaction times, large amounts of washing solvent required, complex post-processing, and low economic benefits. However, Component C offers a simpler preparation process and is more competitive under the same operating conditions.

[0223] The various aspects, embodiments, and features of the present invention should be considered in all respects as illustrative and not limiting, the scope of which is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0224] In the preparation method of the present invention, the order of the steps is not limited to the order listed. Persons skilled in the art will appreciate that variations in the order of the steps are within the scope of the present invention without inventive effort. Furthermore, two or more steps or actions may be performed simultaneously.

[0225] Finally, it should be noted that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit its implementation. Persons skilled in the art may make various modifications, additions, or substitute similar methods for the described specific embodiments. It is not necessary and impossible to provide comprehensive examples of all implementations here. However, obvious variations or modifications arising from the essential spirit of the present invention remain within the scope of protection of the present invention, and interpreting them as any additional limitations would be contrary to the spirit of the present invention.

Claims

1. A hydroxyl-containing DOPO composite flame retardant, characterized in that: It comprises a component A having a structure of formula (I) and a component B having a structure of formula (II), Wherein, R1 and R2 are independently selected from C1 to C 18 An alkylene group, any hydrogen atom on the alkylene group can be independently replaced by a C1-C8 alkyl group, a C6-C 18 Aromatic substitution; R3 and R4 are independently selected from hydrogen, C1-C 18 Alkyl, C3~C 18 Heteroaryl, C6~C 24 Any hydrogen atom on the aromatic ring of the aromatic or heteroaryl group can be replaced independently by any C1 to C 18 Alkyl substitution; x and y are independently selected from 0, 1, 2, 3, 4.

2. A hydroxyl-containing DOPO composite flame retardant according to claim 1, characterized in that: R1 and R2 are independently selected from C1-C8 alkylene groups, and any hydrogen atom on the alkylene group can be independently replaced by a C1-C8 alkyl group; R3 and R4 are independently selected from hydrogen, C1-C8 alkyl, C3-C 18 Heteroaryl, C6~C 18 Aromatic base.

3. A hydroxyl-containing DOPO composite flame retardant according to claim 1 or 2, characterized in that: R1 and R2 are independently selected from methylene, ethylene, propylene, butylene, methyl-substituted methylene, dimethyl-substituted methylene, ethyl-substituted methylene, methyl-substituted ethylene, dimethyl-substituted ethylene, methyl-substituted propylene, dimethyl-substituted propylene, and propyl-substituted propylene; R3 and R4 are independently hydrogen, methyl or ethyl.

4. The hydroxyl-containing DOPO composite flame retardant according to claim 1, characterized in that: In the hydroxyl-containing DOPO composite flame retardant, the content of component A is 50wt%≤100wt%, and the content of component B is 0wt%≤50wt%.

5. A hydroxyl-containing DOPO composite flame retardant according to claim 1 or 4, characterized in that: In the hydroxyl-containing DOPO composite flame retardant, the content of component A is 82wt%≤100wt%, and the content of component B is 0wt%≤18wt%.

6. The method for preparing a hydroxyl-containing DOPO composite flame retardant according to claim 1, characterized in that: The following steps are involved: The compound having the structure of formula (III) and the aliphatic cyclic diketone compound having the structure of formula (IV) are reacted, the reaction conditions are controlled, and purification is performed after the reaction is completed to obtain a mixed product of component A having the structure of formula (I) and component B having the structure of formula (II); Wherein, R3 and R4 are independently selected from hydrogen, C1-C 18 Alkyl, C3~C 18 Heteroaryl, C6~C 24 Any hydrogen atom on the aromatic ring of the aromatic or heteroaryl group can be replaced independently by any C1 to C 18 Alkyl substitution; x and y are independently selected from 0, 1, 2, 3, 4; Wherein, R1 and R2 are independently selected from C1 to C 18 An alkylene group, any hydrogen atom on the alkylene group can be independently replaced by a C1-C8 alkyl group, a C6-C 18 The aromatic group is substituted.

7. The preparation method according to claim 6, characterized in that: The compound having the structure of formula (III) is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

8. The preparation method according to claim 6, characterized in that: The aliphatic cyclic dione compound having the structure of formula (IV) includes one or more of cyclohexanedione, cyclobutanedione, cyclopentanedione, cycloheptanedione, cyclooctanedione, methylcyclohexanedione, dimethylcyclohexanedione, propylcyclohexanedione, tetramethylcyclobutanedione, methylcyclopentanedione, dimethylcyclopentanedione, and ethylcyclopentanedione.

9. The preparation method according to claim 6, characterized in that: The molar ratio of the compound having the structure of formula (III) to the aliphatic cyclic dione compound having the structure of formula (IV) is 1.5 to 10:

1.

10. The preparation method according to claim 6, characterized in that: The reaction time is 0.01 to 25 hours; the reaction temperature is 5 to 250°C.

11. The method for preparing a hydroxyl-containing DOPO composite flame retardant according to claim 1, characterized in that: The method comprises the following steps: physically mixing component A having a structure of formula (I) and component B having a structure of formula (II), wherein in the mixture, the content of component A is 50wt%≤100wt%, and the content of component B is 0wt%≤50wt%.

12. The preparation method according to claim 11, characterized in that: The preparation method of component A having a structure shown in formula (I) comprises the following steps: reacting a compound having a structure shown in formula (III) and an aliphatic cyclic diketone compound having a structure shown in formula (IV), controlling the reaction conditions, and purifying after the reaction is completed to obtain a product, which is component A having a structure shown in formula (I); The preparation method of component B having a structure shown in formula (II) comprises the following steps: reacting a compound having a structure shown in formula (III) and an aliphatic cyclic diketone compound having a structure shown in formula (IV), controlling the reaction conditions, and purifying after the reaction is completed to obtain a product, which is component B having a structure shown in formula (II); Wherein, R3 and R4 are independently selected from hydrogen, C1-C 18 Alkyl, C3~C 18 Heteroaryl, C6~C 24 Any hydrogen atom on the aromatic ring of the aromatic or heteroaryl group can be replaced independently by any C1 to C 18 Alkyl substitution; x and y are independently selected from 0, 1, 2, 3, 4; Wherein, R1 and R2 are independently selected from C1 to C 18 An alkylene group, any hydrogen atom on the alkylene group can be independently replaced by a C1-C8 alkyl group, a C6-C 18 The aromatic group is substituted.

13. A flame retardant polymer material, characterized in that: It comprises a polymer material and the hydroxyl-containing DOPO composite flame retardant as claimed in claim 1.

14. A flame retardant polymer material according to claim 13, characterized in that: The mass fraction of the hydroxyl-containing DOPO composite flame retardant in the flame retardant polymer material is 1 to 50 wt %.

15. A flame retardant epoxy resin, characterized in that: It comprises the hydroxyl-containing DOPO composite flame retardant as claimed in claim 1, an epoxy compound and a curing agent.

16. The method for preparing a flame retardant epoxy resin according to claim 15, characterized in that: The following steps are involved: The epoxy compound, curing agent and hydroxyl-containing DOPO composite flame retardant are melted and stirred at room temperature to 120° C. for 0.1 to 4 hours, and cured at 70 to 90° C., 110 to 130° C. and 160 to 180° C. for 0.5 to 8 hours, respectively, and flame-retardant epoxy resin is obtained after natural cooling.

17. A low-dielectric flame-retardant resin composition, characterized in that: The invention comprises 100 parts by weight of vinyl polyphenylene ether resin and 5 to 150 parts by weight of the hydroxyl-containing DOPO composite flame retardant according to claim 1.

18. A low-dielectric flame-retardant resin composition according to claim 17, characterized in that: The dielectric loss factor of the low-dielectric flame-retardant resin composition is lower than the dielectric loss factor of a composition including the vinyl polyphenylene ether resin but not including the hydroxyl-containing DOPO-based composite flame retardant.

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