A flame retardant and its preparation method and application

Abstract

The present application relates to the technical field of flame retardant, in particular to a kind of flame retardant and its preparation method, and the application of flame retardant in preparing flame retardant epoxy resin.Utilize three functionality boron-containing amino compound and two functionality silicon-containing aldehyde compound under mild conditions to generate hyperbranched schiff base structure compound, then through the addition reaction of P-H bond-containing phosphorus-containing compound and hyperbranched schiff base compound to obtain hyperbranched multi-element halogen-free flame retardant.The flame retardant prepared by the present application contains four kinds of flame-retardant elements such as phosphorus, nitrogen, boron and silicon, realizes the synergistic flame-retardant effect among flame-retardant elements.At the same time, the hyperbranched structure terminal amino group can react with the functional groups in matrix material to form crosslinking network structure, increases the compatibility of flame retardant and matrix material, can significantly improve the flame-retardant efficiency and mechanical properties of polymer.The present application has the advantages of good flame-retardant effect, raw material easy to obtain, mild reaction condition and the like, and wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flame retardant technology, in particular to a flame retardant, a preparation method thereof, and application of the flame retardant in preparation of a flame-retardant epoxy resin. BACKGROUND

[0002] Epoxy resin has been widely used in electronic packaging materials, coatings, composites and other fields due to its excellent processing performance, mechanical properties and good chemical stability. However, the cured product of epoxy resin has the characteristics of extremely flammable, which limits its further application in high-end fields. In addition, as a thermosetting material, the highly cross-linked network structure of the cured epoxy resin leads to high brittleness. Therefore, it is crucial to develop a flame-retardant epoxy cured product with fire safety and high toughness.

[0003] At present, the most effective method to improve the flame retardancy of epoxy resin is to add a flame retardant into the epoxy resin matrix; however, traditional flame retardants often contain elements such as bromine and chlorine, which will release toxic and harmful gases (such as dioxins and hydrogen halides) during combustion, not only causing serious damage to the human respiratory system, nervous system and other systems, but also causing long-term pollution to the atmospheric environment, water and soil, and there is a great safety hazard. With the improvement of people's environmental protection consciousness and health and safety consciousness, the use of safe, environmentally friendly and low-toxicity halogen-free flame retardants is the main research and development trend at present.

[0004] In the previous research, Chinese invention patent application CN117801013A synthesized a hyperbranched phosphorus and nitrogen-containing reactive flame retardant, but did not further apply it to epoxy resin to test its flame retardant effect. Chinese invention patent CN115785456B prepared a hyperbranched macromolecular halogen-free flame retardant and applied it to the flame-retardant modification of polylactic acid and other resin matrices. Although this invention can improve the flame retardancy and thermal stability of polymer composites, its effectiveness for epoxy resin systems still needs to be investigated. Chinese invention patent CN114456547B synthesized a hyperbranched boron-containing flame retardant and prepared a high-strength and high-toughness transparent flame-retardant epoxy resin, but relying solely on the flame retardancy of boron elements cannot achieve satisfactory flame retardant effect with a small amount of addition. Chinese invention patent application CN118185018A prepared a hyperbranched modifier containing phosphorus, nitrogen and silicon elements, and prepared a single-component flame-retardant epoxy resin cured product. Although its flame retardancy and toughness are enhanced, the selection of raw materials is limited, the structure has few variable types, and only contains three flame-retardant elements.

[0005] In summary, the flame retardants disclosed in the prior art can exhibit certain flame retardant effect, but still have defects such as large amount of addition, single action range, limited structure types, etc. SUMMARY

[0006] In the design of flame retardants, the integration of two or more than two flame-retardant elements (phosphorus, nitrogen, silicon, etc.) into the molecular structure of the flame retardant is an effective means to improve its flame-retardant efficiency. On the one hand, the excellent fire safety of epoxy resin cured product is achieved through the synergistic effect between phosphorus-nitrogen, phosphorus-silicon and other elements; on the other hand, hyperbranched polymers have achieved remarkable results in the toughening modification of epoxy resin due to their highly branched structure and abundant intramolecular cavities as well as abundant active end groups. Therefore, a hyperbranched structure flame retardant can be constructed by introducing multiple flame-retardant elements into the hyperbranched molecular structure, so as to realize the flame-retardant and toughening modification of epoxy cured product.

[0007] In order to solve the defects of the prior art, the present application provides a flame retardant and a preparation method and application thereof.

[0008] The first aspect of the present application provides a preparation method of a flame retardant, comprising the following steps:

[0009] (1) mixing boric acid and alcohol amine monomers to generate a dehydration condensation reaction to obtain a trifunctional boron-containing amino compound;

[0010] (2) mixing chlorosilane and aldehyde group-containing phenol monomers to generate a hydrogen chloride removal reaction under the action of an acid-binding agent to obtain a difunctional silicon-containing aldehyde group compound;

[0011] (3) mixing the trifunctional boron-containing amino compound and the difunctional silicon-containing aldehyde group compound to generate a Schiff base reaction to obtain a hyperbranched structure Schiff base intermediate, and then adding a phosphorus-containing compound containing a P-H bond to generate an addition reaction to obtain a hyperbranched multi-element halogen-free flame retardant.

[0012] In some embodiments, the step (1) is specifically: mixing alcohol amine monomers and boric acid according to a molar ratio of (1-5): 1, adding an organic solvent, and reacting at 90-120°C under nitrogen protection and in a device equipped with a water trap for 6-12 hours until no distillate is generated to obtain a trifunctional boron-containing amino compound. The synthesis route map is shown in Figure 1 (S1).

[0013] Further, in step (1), the alcohol amine monomers include one or a combination of more than one of ethanolamine, propanolamine, and isopropanolamine.

[0014] Further, in step (1), the organic solvent includes one or a combination of more than one of benzene, toluene, and xylene, and preferably toluene or xylene.

[0015] Further, in step (1), the molar ratio of boric acid to alcohol amine monomers is 1: (1-5), and preferably 1:3, and the ratio of the amount of organic solvent to boric acid is 10-50 mL: 1 g.

[0016] Further, in step (1), the reaction temperature is 110-115°C, and the reaction time is 6-8 hours.

[0017] In some embodiments, the step (2) is specifically: adding the aldehyde group-containing phenolic monomer into the organic solvent of the aldehyde group-containing phenolic monomer, and adding the acid-binding agent according to the molar ratio of the acid-binding agent to the aldehyde group-containing phenolic monomer being (1-2.2):(1-2). The chlorosilane is added into the reaction system according to the molar ratio of the chlorosilane to the aldehyde group-containing phenolic monomer being 1:2. The reaction is carried out at -10-10°C for 6-12 hours. After the reaction is completed, filtration, rotary evaporation, and drying are performed to obtain the bifunctional silicon-containing aldehyde group compound. The synthesis route map is shown in Figure 1 (S2).

[0018] Further, in step (2), the chlorosilane can be exemplified to include diphenyldichlorosilane, dichlorodimethylsilane, dichlorodiethylsilane, methylphenyldichlorosilane, di-t-butyl dichlorosilane, diisopropyl dichlorosilane, isopropyl methyl dichlorosilane, or t-butyl dichloro (phenylsilane), etc. Optionally, the chlorosilane includes one or more combinations of diphenyldichlorosilane, dichlorodimethylsilane, and methylphenyldichlorosilane.

[0019] Further, in step (2), the aldehyde group-containing phenolic monomer can be exemplified to include p-hydroxybenzaldehyde, 3-methyl-4-hydroxybenzaldehyde, 4-hydroxy-2-methylbenzaldehyde, vanillin, iso-vanillin, and syringaldehyde, etc. Optionally, the aldehyde group-containing phenolic monomer includes one or more combinations of p-hydroxybenzaldehyde, vanillin, and syringaldehyde.

[0020] Further, in step (2), the acid-binding agent can be exemplified to include triethylamine, tripropylamine, pyridine, 4-dimethylaminopyridine, or N,N-diisopropylethylamine, etc. Optionally, the acid-binding agent includes one or more combinations of triethylamine, tripropylamine, and pyridine.

[0021] Further, in step (2), the organic solvent includes one or more combinations of acetone, tetrahydrofuran, dichloromethane, trichloromethane, dioxane, toluene, and xylene, and preferably tetrahydrofuran. The amount of the organic solvent and the aldehyde group-containing phenolic monomer is 10-50 mL:1 g.

[0022] Further, in step (2), the molar ratio of the aldehyde group-containing phenolic monomer, the chlorosilane, and the acid-binding agent is (1-2):1:(1-2.2), and preferably 2:1:1.

[0023] Further, in step (2), the reaction temperature is 0°C, and the reaction time is 8-12 hours.

[0024] In some embodiments, the step (3) is specifically: mixing the trifunctional boron-containing amino compound and the difunctional silicon-containing aldehyde compound according to a molar ratio of (1-2):(1-2) to obtain a mixture, adding an organic solvent, and reacting at 40-70°C in a nitrogen protection device for 4-8 hours to obtain a hyperbranched Schiff base structure intermediate. Subsequently, the P-H bond-containing phosphorus-containing compound and the difunctional silicon-containing aldehyde compound are mixed according to a molar ratio of (1-4):(1-2), the phosphorus-containing compound is added to the reaction system, and the reaction is continued at 40-70°C for 6-12 hours, and finally the organic solvent is removed to obtain a hyperbranched multi-element halogen-free flame retardant. The synthesis route map is shown in Figure 1 (S3).

[0025] Further, in step (3), the P-H bond-containing phosphorus-containing compound can include 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, diphenyl phosphine oxide, diethyl phosphite, dimethyl phosphite, diphenyl phosphite, dibenzyl phosphite, di-n-butyl phosphite, di-t-butyl phosphite, etc.; alternatively, the P-H bond-containing phosphorus-containing compound includes one or more combinations of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, diphenyl phosphine oxide, and diethyl phosphite.

[0026] Further, in step (3), the organic solvent includes one or more combinations of methanol, ethanol, dichloromethane, tetrahydrofuran, and acetonitrile, and is preferably methanol or ethanol. The solvent and the mixture are used in a ratio of 10-50 mL:1 g.

[0027] Further, in step (3), the molar ratio of the P-H bond-containing phosphorus-containing compound, the trifunctional boron-containing amino compound, and the difunctional silicon-containing aldehyde compound is (1-4):(1-2):(1-2), and is preferably 2:1:1.

[0028] Further, in step (3), the reaction temperature is 60-65°C, the reaction time of the trifunctional boron-containing amino compound and the difunctional silicon-containing aldehyde compound is 6 hours to obtain a hyperbranched Schiff base structure intermediate, and the reaction time after adding the phosphorus-containing compound is 8-12 hours to obtain a hyperbranched multi-element halogen-free flame retardant.

[0029] In some embodiments, step (3) is carried out by one-pot method.

[0030] The second aspect of the present application provides a flame retardant, which is formed by "A2+B3" reaction of "A2 monomer" of difunctional silicon-containing aldehyde group compound and "B3 monomer" of trifunctional boron-containing amino compound to form a hyperbranched structure, and then addition reaction of phosphorus-containing compound containing P-H bond, and finally a hyperbranched multi-element halogen-free flame retardant is obtained. The general structure of the flame retardant is:

[0031]

[0032] wherein R1 is alkyl or aryl, R2 is silicon-containing alkyl or silicon-containing aryl, and R3 is phosphorus-containing alkyl or phosphorus-containing aryl.

[0033] The third aspect of the present application provides a use of the flame retardant as described above in the preparation of a flame-retardant epoxy resin.

[0034] In some embodiments, the preparation method of the flame-retardant epoxy resin comprises the following steps:

[0035] The flame retardant and the epoxy resin prepolymer are stirred at 80-100℃ for 15-30 minutes to form a uniform liquid, then the curing agent is added and stirred until dissolved, and then the mixture is quickly poured into a preheated mold, and then the mold is placed in a forced air drying oven and cured at 120-180℃ for 6-10 hours, and then a flame-retardant epoxy resin is obtained after cooling.

[0036] Optionally, the mass ratio of the epoxy resin prepolymer, the curing agent and the flame retardant is 100: (25-80): (2-10).

[0037] Optionally, the curing conditions are: curing at 120℃, 140℃, 160℃, 180℃ for 1-3 hours.

[0038] Optionally, the curing conditions are: curing at 120℃, 150℃, 180℃ for 1-3 hours.

[0039] Optionally, the curing conditions are: curing at 130℃, 160℃, 180℃ for 1-3 hours.

[0040] Further, the epoxy resin is one or more of a combination of one or more of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, alicyclic epoxy resin, o-cresol novolac epoxy resin, bisphenol A novolac epoxy resin, phenol novolac epoxy resin, dicyclopentadiene novolac epoxy resin, and phenol-biphenyl epoxy resin.

[0041] Still further, the curing agent is one or more of a combination of one or more of acid anhydride, polyamine, dicyandiamide or phenolic resin.

[0042] Beneficial effects:

[0043] The present invention provides a flame retardant and its preparation method and application, which have the following advantages:

[0044] (1) The flame retardant prepared by the present invention does not contain halogen elements, is safe and environmentally friendly, and through structural design, the hyperbranched structure contains four flame retardant elements (phosphorus, nitrogen, boron, and silicon) at the same time, which has the advantage of high flame retardant efficiency through synergistic flame retardant effect;

[0045] (2) The hyperbranched multi-element halogen-free flame retardant prepared by the present invention can not only improve the flame retardancy of the resin matrix, but also improve the mechanical properties of the resin, thereby enhancing the comprehensive performance of the resin;

[0046] (3) The hyperbranched flame retardant of the present invention has abundant amino groups at the ends of its molecular structure, which can undergo cross-linking reaction with the reactive functional groups in the matrix material and promote the cross-linking process of the matrix material, thereby helping to improve the compatibility of the flame retardant in the matrix resin.

[0047] (4) The raw materials used in the synthesis process of the flame retardant of the present invention are rich in sources and a wide variety of types can be selected. The structure of the final product is adjustable, and the flame retardant properties can be precisely controlled according to actual application needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of the synthetic route for preparing the hyperbranched multi-element halogen-free flame retardant of the present invention;

[0049] Figure 2 Schematic diagram of the structure of the hyperbranched multi-element halogen-free flame retardant obtained in Example 1 of the present invention;

[0050] Figure 3 This is an infrared spectrum of the hyperbranched multi-element halogen-free flame retardant obtained in Example 1 of the present invention;

[0051] Figure 4 This is the nuclear magnetic resonance phosphorus spectrum of the hyperbranched multi-element halogen-free flame retardant obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0052] The present invention is further described below with reference to the embodiments and drawings, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention fall within the scope of protection of the present invention.

[0053] Example 1

[0054] This embodiment provides a hyperbranched multi-element halogen-free flame retardant and its preparation method. The structural formula of the hyperbranched multi-element halogen-free flame retardant is shown in Figure 2 .

[0055] The preparation method of the hyperbranched multi-element halogen-free flame retardant comprises the following steps:

[0056] (1) 6.18 g of boric acid and 18.3 g of ethanolamine are added to a 250 mL three-necked flask equipped with a water separator and a nitrogen inlet, 100 mL of toluene is added, and the temperature is raised to 110°C for stirring for 8 hours. After the reaction is completed, the organic solvent is removed by rotary evaporation, and vacuum drying is performed overnight to obtain a yellowish viscous liquid 18 g, a yield of 97%, which is a three-functionality boron-containing amino compound.

[0057] (2) 6.08 g of vanillin is added to a 100 mL three-necked flask, and 60 mL of tetrahydrofuran is added, followed by the addition of 4.4 g of triethylamine as an acid binding agent. After magnetic stirring at 0°C for 30 minutes, 3.58 g of dichlorodimethylsilane is added dropwise into the solution, and the reaction is maintained at 0°C for 12 hours. After the reaction is completed, filtration, rotary evaporation, and vacuum drying are performed to obtain 6.64 g of a yellowish solid powder, a yield of 92%, which is a two-functionality silicon-containing aldehyde group compound.

[0058] (3) 1.9 g of the product of the first step (three-functionality boron-containing amino compound) and 3.6 g of the product of the second step (two-functionality silicon-containing aldehyde group compound) are added to a 250 mL three-necked flask, 100 mL of ethanol is added, and the reaction is refluxed at 60°C for 6 hours to obtain a hyperbranched Schiff base structure intermediate. Then 4.32 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added to the three-necked flask, and the reaction is continued for 12 hours. After the reaction is completed, the organic solvent is removed by rotary evaporation, purified, and vacuum dried to obtain a yellowish powder 7.81 g, a yield of 84%, which is a hyperbranched multi-element halogen-free flame retardant.

[0059] Figure 3 、 Figure 4 are the infrared spectrum and the nuclear magnetic resonance phosphorus spectrum of the obtained hyperbranched multi-element halogen-free flame retardant, respectively.

[0060] Example 2

[0061] The present embodiment provides a preparation method of a hyperbranched multi-element halogen-free flame retardant, comprising the following steps:

[0062] (1) 6.18 g of boric acid and 22.5 g of propanolamine are added to a 250 mL three-necked flask equipped with a water separator and a nitrogen inlet, 110 mL of dimethylbenzene is added, and the temperature is raised to 115°C for stirring for 8 hours. After the reaction is completed, the organic solvent is removed by rotary evaporation, and vacuum drying is performed overnight to obtain a yellowish viscous liquid 22 g, a yield of 94%, which is a three-functionality boron-containing amino compound.

[0063] (2) 7.28 g of syringaldehyde was added into a 100 mL three-necked flask, and 60 mL of tetrahydrofuran was added, followed by the addition of 5.8 g of tripropylamine as an acid-binding agent. After magnetic stirring at 0°C for 30 minutes, 3.82 g of methylphenyldichlorosilane was added dropwise into the solution, and the reaction was maintained at 0°C for 8 hours. After the reaction was completed, filtration, rotary evaporation, and vacuum drying were performed to obtain 9.1 g of a light yellow solid powder with a yield of 95%, which was a difunctional silicon-containing aldehyde-based compound.

[0064] (3) 2.3 g of the product of the first step (a trifunctional boron-containing amino compound) and 4.2 g of the product of the second step (a difunctional silicon-containing aldehyde-based compound) were added into a 250 mL three-necked flask, 100 mL of methanol was added, and the reaction was performed at 65°C under reflux for 6 hours to obtain a hyperbranched Schiff base structure intermediate. Then, 4.04 g of diphenyl phosphine oxide was added into the three-necked flask, and the reaction was continued for 12 hours. After the reaction was completed, the organic solvent was removed by rotary evaporation, purification was performed, and vacuum drying was performed to obtain a light yellow powder of 8.71 g with a yield of 83%, which was a hyperbranched multi-element halogen-free flame retardant.

[0065] Example 3

[0066] The present example provides a method for preparing a hyperbranched multi-element halogen-free flame retardant, which comprises the following steps:

[0067] (1) 6.18 g of boric acid and 22.5 g of isopropanolamine were added into a 250 mL three-necked flask equipped with a water separator and a nitrogen inlet, 110 mL of toluene was added, and the temperature was raised to 110°C for continuous stirring for 6 hours. After the reaction was completed, the organic solvent was removed by rotary evaporation, and vacuum drying was performed overnight to obtain a light yellow viscous liquid of 21.5 g with a yield of 92%, which was a trifunctional boron-containing amino compound.

[0068] (2) 7.28 g of syringaldehyde was added into a 100 mL three-necked flask, and 60 mL of tetrahydrofuran was added, followed by the addition of 5.8 g of tripropylamine as an acid-binding agent. After magnetic stirring at 0°C for 30 minutes, 3.82 g of methylphenyldichlorosilane was added dropwise into the solution, and the reaction was maintained at 0°C for 8 hours. After the reaction was completed, filtration, rotary evaporation, and vacuum drying were performed to obtain 9.1 g of a light yellow solid powder with a yield of 95%, which was a difunctional silicon-containing aldehyde-based compound.

[0069] (3) 2.3 g of the product of the first step (a trifunctional boron-containing amino compound) and 4.8 g of the product of the second step (a difunctional silicon-containing aldehyde-based compound) were added into a 250 mL three-necked flask, 100 mL of methanol was added, and the reaction was performed at 65°C under reflux for 6 hours to obtain a hyperbranched Schiff base structure intermediate. Then, 2.76 g of diethyl phosphite was added into the three-necked flask, and the reaction was continued for 8 hours. After the reaction was completed, the organic solvent was removed by rotary evaporation, purification was performed, and vacuum drying was performed to obtain a light yellow powder of 9.06 g with a yield of 92%, which was a hyperbranched multi-element halogen-free flame retardant.

[0070] Example 4

[0071] The present example provides an application of the hyperbranched multi-element halogen-free flame retardant in the preparation of a flame-retardant epoxy resin, and the preparation method of the flame-retardant epoxy resin comprises the following steps:

[0072] The hyperbranched multi-element halogen-free flame retardant prepared in Example 1 (3.86g, accounting for 3wt% of the total system) was stirred with 100g of epoxy resin prepolymer at 100°C for 30 minutes to form a uniform liquid, then 25g of curing agent (4,4-diamino diphenyl methane) was added and stirred until dissolved, then quickly poured into a preheated stainless steel mold to 100°C, then the mold was placed in a forced air drying oven, and cured at 120°C, 140°C, 160°C, 180°C for 2 hours respectively, and then cooled to obtain a flame-retardant epoxy resin sample.

[0073] Example 5

[0074] The present example provides an application of the hyperbranched multi-element halogen-free flame retardant in the preparation of a flame-retardant epoxy resin, and the preparation method of the flame-retardant epoxy resin comprises the following steps:

[0075] The hyperbranched multi-element halogen-free flame retardant prepared in Example 1 (7.98g, accounting for 6wt% of the total system) was stirred with 100g of epoxy resin prepolymer at 100°C for 30 minutes to form a uniform liquid, then 25g of curing agent (4,4-diamino diphenyl methane) was added and stirred until dissolved, then quickly poured into a preheated stainless steel mold to 100°C, then the mold was placed in a forced air drying oven, and cured at 120°C, 140°C, 160°C, 180°C for 2 hours respectively, and then cooled to obtain a flame-retardant epoxy resin sample.

[0076] Example 6

[0077] The present example provides an application of the hyperbranched multi-element halogen-free flame retardant in the preparation of a flame-retardant epoxy resin, and the preparation method of the flame-retardant epoxy resin comprises the following steps:

[0078] The hyperbranched multi-element halogen-free flame retardant prepared in Example 1 (12.36g, accounting for 9wt% of the total system) was stirred with 100g of epoxy resin prepolymer at 100°C for 30 minutes to form a uniform liquid, then 25g of curing agent (4,4-diamino diphenyl methane) was added and stirred until dissolved, then quickly poured into a preheated stainless steel mold to 100°C, then the mold was placed in a forced air drying oven, and cured at 120°C, 140°C, 160°C, 180°C for 2 hours respectively, and then cooled to obtain a flame-retardant epoxy resin sample.

[0079] Example 7

[0080] The present embodiment provides an application of the hyperbranched multi-element halogen-free flame retardant in the preparation of a flame-retardant epoxy resin, and the preparation method of the flame-retardant epoxy resin comprises the following steps:

[0081] The hyperbranched multi-element halogen-free flame retardant prepared in Example 2 (2.55 g, 2 wt% of the total system) was stirred with 100 g of an epoxy resin prepolymer at 95°C for 30 minutes to form a uniform liquid, then 25 g of a curing agent (4,4-diaminodiphenyl methane) was added and stirred until dissolved, then quickly poured into a preheated stainless steel mold to 100°C, then the mold was placed in a forced air drying oven, and cured at 120°C, 150°C and 180°C for 2 hours respectively, and then cooled to obtain a flame-retardant epoxy resin sample.

[0082] Example 8

[0083] The present embodiment provides an application of the hyperbranched multi-element halogen-free flame retardant in the preparation of a flame-retardant epoxy resin, and the preparation method of the flame-retardant epoxy resin comprises the following steps:

[0084] The hyperbranched multi-element halogen-free flame retardant prepared in Example 2 (6.57 g, 5 wt% of the total system) was stirred with 100 g of an epoxy resin prepolymer at 95°C for 30 minutes to form a uniform liquid, then 25 g of a curing agent (4,4-diaminodiphenyl methane) was added and stirred until dissolved, then quickly poured into a preheated stainless steel mold to 100°C, then the mold was placed in a forced air drying oven, and cured at 120°C, 150°C and 180°C for 2 hours respectively, and then cooled to obtain a flame-retardant epoxy resin sample.

[0085] Example 9

[0086] The present embodiment provides an application of the hyperbranched multi-element halogen-free flame retardant in the preparation of a flame-retardant epoxy resin, and the preparation method of the flame-retardant epoxy resin comprises the following steps:

[0087] The hyperbranched multi-element halogen-free flame retardant prepared in Example 2 (10.86 g, 8 wt% of the total system) was stirred with 100 g of an epoxy resin prepolymer at 95°C for 30 minutes to form a uniform liquid, then 25 g of a curing agent (4,4-diaminodiphenyl methane) was added and stirred until dissolved, then quickly poured into a preheated stainless steel mold to 100°C, then the mold was placed in a forced air drying oven, and cured at 120°C, 150°C and 180°C for 2 hours respectively, and then cooled to obtain a flame-retardant epoxy resin sample.

[0088] Example 10

[0089] The present embodiment provides an application of the hyperbranched multi-element halogen-free flame retardant in the preparation of a flame-retardant epoxy resin, and the preparation method of the flame-retardant epoxy resin comprises the following steps:

[0090] The hyperbranched multi-element halogen-free flame retardant prepared in Example 3 (2.55 g, 2 wt% of the total system) was stirred with 100 g of epoxy resin prepolymer at 95°C for 30 minutes to form a uniform liquid, then 25 g of curing agent (4,4-diaminodiphenyl methane) was added and stirred until dissolved, then quickly poured into a stainless steel mold preheated to 100°C, then the mold was placed in a forced air drying oven, and cured at 130°C, 160°C, and 180°C for 2 hours each, and after cooling, a flame-retardant epoxy resin sample was obtained.

[0091] Example 11

[0092] This example provides a use of a hyperbranched multi-element halogen-free flame retardant in the preparation of a flame-retardant epoxy resin, the preparation method of the flame-retardant epoxy resin comprising the following steps:

[0093] The hyperbranched multi-element halogen-free flame retardant prepared in Example 3 (5.2 g, 4 wt% of the total system) was stirred with 100 g of epoxy resin prepolymer at 95°C for 30 minutes to form a uniform liquid, then 25 g of curing agent (4,4-diaminodiphenyl methane) was added and stirred until dissolved, then quickly poured into a stainless steel mold preheated to 100°C, then the mold was placed in a forced air drying oven, and cured at 130°C, 160°C, and 180°C for 2 hours each, and after cooling, a flame-retardant epoxy resin sample was obtained.

[0094] Example 12

[0095] This example provides a use of a hyperbranched multi-element halogen-free flame retardant in the preparation of a flame-retardant epoxy resin, the preparation method of the flame-retardant epoxy resin comprising the following steps:

[0096] The hyperbranched multi-element halogen-free flame retardant prepared in Example 3 (7.98 g, 6 wt% of the total system) was stirred with 100 g of epoxy resin prepolymer at 95°C for 30 minutes to form a uniform liquid, then 25 g of curing agent (4,4-diaminodiphenyl methane) was added and stirred until dissolved, then quickly poured into a stainless steel mold preheated to 100°C, then the mold was placed in a forced air drying oven, and cured at 130°C, 160°C, and 180°C for 2 hours each, and after cooling, a flame-retardant epoxy resin sample was obtained.

[0097] Comparative Example 1

[0098] This example provides a use of a hyperbranched multi-element halogen-free flame retardant in the preparation of a flame-retardant epoxy resin, the preparation method of the flame-retardant epoxy resin comprising the following steps:

[0099] Take 25 g of epoxy resin prepolymer and 5 g of curing agent (4,4-diamino diphenyl methane) to form a uniform liquid at 90°C, quickly pour into a preheated to 100°C stainless steel mold, then put the mold into a forced air drying oven, at 120°C, 140°C, 160°C, 180°C each for 2 hours, after cooling to get epoxy resin sample, for further comparative test.

[0100] Comparative Example 2

[0101] The present comparative example provides an application of a hyperbranched multi-element halogen-free flame retardant in the preparation of a flame-retardant epoxy resin, the preparation method of the flame-retardant epoxy resin comprising the following steps:

[0102] Take 25 g of epoxy resin prepolymer and 5 g of curing agent (4,4-diamino diphenyl methane) to form a uniform liquid at 90°C, quickly pour into a preheated to 100°C stainless steel mold, then put the mold into a forced air drying oven, at 120°C, 140°C, 160°C, 180°C each for 2 hours, after cooling to get epoxy resin sample, for further comparative test.

[0103] Comparative Example 3

[0104] The present comparative example provides an application of a hyperbranched multi-element halogen-free flame retardant in the preparation of a flame-retardant epoxy resin, the preparation method of the flame-retardant epoxy resin comprising the following steps:

[0105] Take 25 g of epoxy resin prepolymer and 5 g of curing agent (4,4-diamino diphenyl methane) to form a uniform liquid at 90°C, quickly pour into a preheated to 100°C stainless steel mold, then put the mold into a forced air drying oven, at 120°C, 140°C, 160°C, 180°C each for 2 hours, after cooling to get epoxy resin sample, for further comparative test.

[0106] The epoxy resin prepolymer in Examples 4-12 and Comparative Examples 1-3 is a bisphenol A type epoxy resin, sourced from Nantong Xingchen Synthetic Material Co., Ltd., with a model number of E-51.

[0107] Performance test

[0108] The flame-retardant performance and mechanical properties of the flame-retardant epoxy resin were determined, and the determination method of each index was:

[0109] Vertical burning grade: determined according to ASTM D3801 method.

[0110] Limiting oxygen index: determined according to ASTM D2863 method.

[0111] Flexural strength and flexural modulus: determined according to ASTM D790 method.

[0112] Initial decomposition temperature: generally defined as the decomposition temperature point corresponding to the 5% mass loss of the sample.

[0113] Residual carbon content: generally defined as the final residual mass percentage of the sample at the end of the thermal gravimetric test.

[0114] The performance test data of the flame-retardant epoxy resin added with the hyperbranched multi-element halogen-free flame retardant prepared in Example 1 are shown in Table 1.

[0115] Table 1. Flame-retardant performance test data of the cured product of the flame-retardant epoxy resin prepared in Example 1

[0116]

[0117] As shown in Table 1, the test results of Comparative Examples 4-6 and Comparative Example 1 can show that: adding about 6-9 wt% of the hyperbranched multi-element halogen-free flame retardant prepared in Example 1 can obviously improve the limiting oxygen index and vertical burning grade of the epoxy resin sample, the residual carbon content is also increased, and the mechanical properties are also obviously improved; it shows that the flame retardant modified epoxy resin of the present application can significantly improve the flame retardant performance of the epoxy resin.

[0118] The performance test data of the flame-retardant epoxy resin added with the hyperbranched multi-element halogen-free flame retardant prepared in Example 2 are shown in Table 2.

[0119] Table 2. Flame-retardant performance test data of the cured product of the flame-retardant epoxy resin prepared in Example 2

[0120]

[0121] As shown in Table 2, the test results of Comparative Examples 7-9 and Comparative Example 2 can show that: adding about 5-8 wt% of the hyperbranched multi-element halogen-free flame retardant prepared in Example 2 can obviously improve the limiting oxygen index and vertical burning grade of the epoxy resin sample, the residual carbon content is also increased, and the mechanical properties are also obviously improved; it shows that the flame retardant modified epoxy resin of the present application can significantly improve the flame retardant performance of the epoxy resin.

[0122] The performance test data of the flame-retardant epoxy resin added with the hyperbranched multi-element halogen-free flame retardant prepared in Example 3 are shown in Table 3.

[0123] Table 3. Flame-retardant performance test data of the cured product of the flame-retardant epoxy resin prepared in Example 3

[0124]

[0125] As shown in Table 3, the test data of Comparative Examples 10-12 and Comparative Example 3 can show that: adding about 4-6 wt% of the hyperbranched multi-element halogen-free flame retardant prepared in Example 3 of the present application can obviously improve the limiting oxygen index and vertical burning grade of the epoxy resin sample, the residual carbon content is also increased, and the mechanical properties are also obviously improved; it shows that the flame retardant modified epoxy resin of the present application can significantly improve the flame retardant performance of the epoxy resin.

[0126] 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 to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A process for the preparation of a flame retardant, characterized in that, The method comprises the following steps: (1) mixing boric acid and alcohol amine monomers to generate a dehydration condensation reaction to obtain a trifunctional boron-containing amino compound; (2) mixing a chlorine-containing silane and an aldehyde group-containing phenol monomer to generate a hydrogen chloride removal reaction under the action of an acid-binding agent to obtain a difunctional silicon-containing aldehyde group compound; (3) mixing the trifunctional boron-containing amino compound and the difunctional silicon-containing aldehyde group compound to generate a Schiff base reaction to obtain a hyperbranched structure Schiff base intermediate, and then adding a phosphorus-containing compound containing a P-H bond to generate an addition reaction to obtain a hyperbranched multi-element halogen-free flame retardant; In step (1), the molar ratio of the boric acid to the alcohol amine monomers is 1:3; In step (2), the chlorine-containing silane comprises one or more of a combination of diphenyldichlorosilane, dichlorodimethylsilane, and methylphenyldichlorosilane; In step (2), the molar ratio of the aldehyde group-containing phenol monomer, the chlorine-containing silane, and the acid-binding agent is 2:1:

1.

2. The method of claim 1, wherein: In step (1), the alcohol amine monomer comprises one or more of a combination of ethanolamine, propanolamine, and isopropanolamine.

3. The method of claim 1, wherein: In step (2), the aldehyde group-containing phenol monomer comprises one or more of a combination of p-hydroxybenzaldehyde, vanillin, and syringaldehyde.

4. The method of claim 1, wherein: In step (2), the acid-binding agent comprises one or more of a combination of triethylamine, tripropylamine, and pyridine.

5. The process for the preparation of the flame retardant according to claim 1, characterized by the fact that: In step (3), the phosphorus-containing compound containing a P-H bond comprises one or more of a combination of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, diphenyl phosphine oxide, and diethyl phosphite.

6. The method of claim 1, wherein: In step (3), the molar ratio of the phosphorus-containing compound containing a P-H bond, the trifunctional boron-containing amino compound, and the difunctional silicon-containing aldehyde group compound is (1-4):(1-2):(1-2).

7. A flame retardant prepared according to the process of any one of claims 1 to 6, characterized in that The structural general formula of the flame retardant is: wherein R1 is an alkylene group or an arylene group, R2 is a silicon-containing alkylene group or a silicon-containing arylene group, and R3 is a phosphorus-containing alkyl group or a phosphorus-containing aryl group.

8. Use of a flame retardant prepared according to the process of any one of claims 1 to 6 or of a flame retardant according to claim 7 for the preparation of a flame-retardant epoxy resin, characterized in that The preparation method of the flame-retardant epoxy resin comprises the following steps: The flame retardant and the epoxy resin prepolymer are stirred at 80-100°C for 15-30 minutes to form a uniform liquid, then a curing agent is added and stirred until dissolved, and then the mixture is quickly poured into a preheated mold, and then the mold is placed in a forced air drying oven and cured at 120-180°C for 6-10 hours; after cooling, a flame-retardant epoxy resin is obtained.

9. Use according to claim 8, characterized in that, The mass ratio of the epoxy resin prepolymer, the curing agent, and the flame retardant is 100:(25-80):(2-10).

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