Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a preparation method and application of a benzoxazine-based modified thiol epoxy curing agent. Through the reaction of benzoxazine and mercaptan, a tertiary amine structure is introduced into the modified mercaptan curing agent, so that the smell of the mercaptan curing agent is reduced, the defects of high free formaldehyde content and the like of the traditional Mannich base modified mercaptan curing agent can be overcome, the requirements of environmental protection are met, and the application of the coating, the adhesive, the composite material and the like is expanded.
A benzoxazine-based modified thiol epoxy curing agent has a structural formula shown in formula (1):
wherein R is1The corresponding phenol is selected from one or more of phenol, o-methyl phenol, M-methyl phenol, p-methyl phenol, o-allyl phenol, p-allyl phenol, guaiacol, salicylaldehyde, vanillin, eugenol, naphthol, p-halophenol, p-diphenol, resorcinol, bisphenol S, bisphenol A, bisphenol F, bisphenol E, bisphenol B, bisphenol M and bisphenol Z;
R2the corresponding amine is selected from aniline, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-xylylenediamine, naphthylamine, benzylamine, methylbenzylamine, p-aminobenzylamine, benzidine, 4 '-diaminodiphenylmethane, p-methylaniline, o-methylaniline, m-methylaniline, 4-ethylaniline, o-chloroaniline, m-chloroaniline, p-chloroaniline, 3, 5-dimethylaniline, 4' -diaminodiphenyl ether, furfurylamine, methylamine, ethylamine, propylamine, isopropylamine, butylamine, tert-butylamine, cyclohexylamine, 1,3, 5-triaminobenzene, N-bis (3-aminopropyl) methylamine, N-dimethyl-1, 3-diaminopropane, tetramethylpropylenediamine, dimethyldipropylenetriamine, 4-dimethylaminobutylamine, N-methyl-1, 3-propanediamine, N, N-tetrakis (3-aminopropyl) -1, 4-butanediamine, tris (3-aminopropyl) amine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethylenepolyamine, divinylpropylamine, 1, 6-hexanediamine, ethylenediamine, N, N-bis (2-aminoethyl) -1, 2-ethylenediamine, N-methyl-2, 2-diaminodiethylamine, trientine impurity, 4' -diaminodicyclohexylmethane, 3 ' -dimethyl-4, 4' -diaminodicyclohexylmethane, methylcyclohexanediamine, aminoethylpiperazine, methylcyclopentamine, o-diaminomethylcyclopentane, (2, 3-dimethyl) dibutylenetriamine, triaminononane, tetramethylenediamine, triaminononane, triaminetriamine, and mixtures thereof, One or more of dicyandiamide, adipic acid dihydrazide, mixed amine and hybrid amine;
R3the corresponding polythiol is selected from pentaerythritol tetrakis (3-mercaptopropionate), trimethylolpropane tris (3-mercaptopropionate), trimethylolethane tris (3-mercaptopropionate), inositol hexakis (mercaptopropionate), tetraethyleneglycol bis (3-Mercaptopropionic acid), pentaerythritol tetrakis (3-mercaptobutanoate), cyanuric acid, dimercaptoethyl sulfide, 3, 6-dioxo-1, 8-octanedithiol, 2, 3-butanedithiol, 1, 5-pentanedithiol, 1, 4-benzenedithiol, 4-biphenyldithiol, 1, 2-benzenedimethylthiol, bis (2-mercaptoethyl) ether, 1, 2-ethanedithiol, 1, 3-propanedithiol, 1, 6-hexanedithiol, 1, 9-nonanedithiol, 1, 8-octanedithiol, 1, 16-hexadecanedithiol, 2, 3-dithio (2-mercapto) -1-propanethiol, 1, 4-benzenedimethylthiol, 1, 2-butanedithiol, 1, 10-decanedithiol, 1, 3-decanedithiol, One or more of Karenz MT NR1 trifunctional thiols;
the value range of n is that n is more than or equal to 2.
According to the second technical scheme, the preparation method of the benzoxazine-based modified thiol epoxy curing agent comprises the following steps:
performing ring-opening reaction on benzoxazine and polythiol to obtain the benzoxazine modified thiol epoxy curing agent, wherein the structural formula of the benzoxazine is shown as a formula (2):
the specific reaction route is as follows:
further, the polythiol is selected from pentaerythritol tetrakis (3-mercaptopropionate), trimethylolpropane tris (3-mercaptopropionate), trimethylolethane tris (3-mercaptopropionate), inositol hexakis (mercaptopropionate), tetraethyleneglycol bis (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptobutyrate), cyanuric acid, dimercaptoethyl sulfide, 3, 6-dioxo-1, 8-octanedithiol, 2, 3-butanedithiol, 1, 5-pentanethiol, 1, 4-benzenedithiol, 4-biphenyldithiol, 1, 2-benzenedimethylthiol, bis (2-mercaptoethyl) ether, 1, 2-ethanedithiol, 1, 3-propanedithiol, 1, 6-hexanedithiol, 1, 6-hexanedithiol, and mixtures thereof, 1, 9-nonanedithiol, 1, 8-octanedithiol, 1, 16-hexadecanedithiol, 2, 3-dithio (2-mercapto) -1-propanethiol, 1, 4-benzenedimethylmercaptan, 1, 2-butanedithiol, 1, 10-decanedithiol, and Karenz MT NR1 trifunctional thiol.
Further, the molar ratio of the benzoxazine to the polythiol is (1-4) to (1-20), and the ring-opening reaction specifically comprises the following steps: reacting for 2-24h at 30-140 ℃ under inert atmosphere.
Further, the benzoxazine is prepared by a Mannich reaction of a phenol source, an amine source and aldehyde in a solvent. The specific reaction route is as follows:
further, the phenol source is one or more of phenol, o-methyl phenol, M-methyl phenol, p-methyl phenol, o-allyl phenol, p-allyl phenol, guaiacol, salicylaldehyde, vanillin, eugenol, naphthol, p-halophenol, p-diphenol, resorcinol, bisphenol S, bisphenol a, bisphenol F, bisphenol E, bisphenol B, bisphenol M, bisphenol Z, and the aldehyde is formaldehyde or paraformaldehyde.
Further, the amine source is aniline, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-xylylenediamine, naphthylamine, benzylamine, methylbenzylamine, p-aminobenzylamine, benzidine, 4 '-diaminodiphenylmethane, p-methylaniline, o-methylaniline, m-methylaniline, 4-ethylaniline, o-chloroaniline, m-chloroaniline, p-chloroaniline, 3, 5-dimethylaniline, 4' -diaminodiphenyl ether, furfurylamine, methylamine, ethylamine, propylamine, isopropylamine, butylamine, t-butylamine, octadecylamine, cyclohexylamine, 1,3, 5-triaminobenzene, N-bis (3-aminopropyl) methylamine, N-dimethyl-1, 3-diaminopropane, tetramethylpropylenediamine, dimethyldipropylenetriamine, 4-dimethylaminobutylamine, N-methyl-1, 3-propanediamine, N, N-tetrakis (3-aminopropyl) -1, 4-butanediamine, tris (3-aminopropyl) amine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethylenepolyamine, divinylpropylamine, 1, 6-hexanediamine, ethylenediamine, N, N-bis (2-aminoethyl) -1, 2-ethylenediamine, N-methyl-2, 2-diaminodiethylamine, trientine impurity, 4' -diaminodicyclohexylmethane, 3 ' -dimethyl-4, 4' -diaminodicyclohexylmethane, methylcyclohexanediamine, aminoethylpiperazine, methylcyclopentamine, o-diaminomethylcyclopentane, (2, 3-dimethyl) dibutylenetriamine, triaminononane, tetramethylenediamine, triaminononane, triaminetriamine, and mixtures thereof, One or more of dicyandiamide, adipic acid dihydrazide, mixed amine and hybrid amine.
Further, the molar ratio of the phenol source to the amine source to the aldehyde is 1:1: 2.0-2.5; the solvent is one or more of water, toluene, 1, 4-dioxane, cyclohexanone, ethyl acetate, trichloromethane, xylene, butanone, methyl isobutyl ketone, DMF, DMAc and NMP; the total mass fraction of the phenol source, the amine source and the aldehyde in the solvent is 20-90%.
Further, the method specifically comprises the following steps: and (3) placing the phenol source and the aldehyde into a solvent, uniformly mixing, then adding the amine source in batches, heating to 80-110 ℃, stirring and reacting for 4-12 hours to obtain the product benzoxazine.
According to the third technical scheme, the benzoxazine-based modified thiol epoxy curing agent is applied to adhesives, coatings and composite materials cured at medium temperature and/or low temperature.
Further, the medium temperature range is 80-110 ℃, and the room temperature range is 20-40 ℃.
Compared with the prior art, the invention has the beneficial effects that:
the invention adopts a two-step method, wherein the benzoxazine is synthesized by the Mannich reaction of phenol, amine and aldehyde, and then the benzoxazine is adopted to modify different polythiol compounds, so as to finally form the benzoxazine modified thiol curing agent. Due to the flexible molecular structure design of benzoxazine and the diversity of thiol compounds, different benzoxazines and thiol compounds can be adopted for regulation and control, so that a modified thiol curing agent system suitable for different use requirements is designed, a convenient and effective thiol curing agent modification method is provided, and the types of thiol curing agents are greatly enriched.
According to the curing agent disclosed by the invention, a tertiary amine structure is introduced into a molecular structure of the curing agent due to the access of benzoxazine, so that the reaction between an epoxy group and a thiol compound is promoted, and a tertiary amine accelerator is not required to be additionally added. Through benzoxazine modification, the molecular weight of the thiol curing agent is adjusted, so that the pungent smell of the thiol curing agent can be reduced or eliminated, and the construction conditions are improved. In addition, the use of excessive formaldehyde can be eliminated through a two-step synthesis process, so that the formaldehyde content in the mercaptan curing agent is effectively controlled, and the effect of environmental protection is achieved.
The benzoxazine modified thiol epoxy curing agent is prepared by two-step reaction: the first step is to synthesize benzoxazine, and the second step is to add polythiol to open the oxazine ring to obtain benzoxazine modified thiol curing agent. According to the invention, through the reaction of benzoxazine and mercaptan, a tertiary amine structure is introduced into the modified mercaptan curing agent, so that the curing reaction of mercaptan and epoxy resin is promoted. The structure of the tertiary amine can be divided into aliphatic and aromatic, the activity of the tertiary amine in the aliphatic is higher than that of the aromatic, namely, the curing agent containing the aliphatic tertiary amine structure has lower temperature and shorter time required by the curing of the epoxy resin in the using process; and the more the tertiary amine structures in the modified thiol curing agent are in a certain range, the shorter the time required for curing the epoxy resin is, and the lower the curing temperature is. The adjustment of curing temperature and curing time is realized by regulating and controlling the type and the content of a tertiary amine structure in the structure of the modified mercaptan curing agent, and different process conditions and performance requirements of the epoxy resin are met. The benzoxazine is introduced into the mercaptan curing agent, so that the smell of the mercaptan curing agent is reduced, the defects of high free formaldehyde content and the like of the traditional Mannich base modified mercaptan curing agent can be overcome, the requirements of environmental protection are met, and the application of the coating, the adhesive, the composite material and the like is expanded.
Detailed Description
Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.
It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.
Example 1
18.82g (0.2mol) of phenol, 13.2g (0.44mol) of paraformaldehyde and 200mL of toluene are sequentially added into a three-neck flask provided with a mechanical stirrer, a condenser and a thermometer, and the three-neck flask is placed in an oil bath to slowly raise the temperature to 55 ℃; and then adding 20.44g (0.2mol) of N, N-dimethyl-1, 3-diaminopropane at intervals of 15min in three batches, wherein the mass fraction of solute in the system is 30%, heating to 85 ℃ after the N, N-dimethyl-1, 3-diaminopropane is completely added, stirring for reacting for 4h, washing and drying after the reaction is finished to obtain light yellow liquid, namely benzoxazine P-dampa, the structure of which is shown in formula (3), and the yield is 92.7%.
The prepared benzoxazine was subjected to infrared spectroscopic analysis, and the results are shown in fig. 1. As can be seen from the figure, 921cm-1Is a characteristic absorption peak of the oxazine ring of 1034cm-1And stretching vibration peak of C-O-C, 1137cm-1The peak of C-N-C stretching vibration is shown. Therefore, the structure of the synthesized benzoxazine P-dampa is correct.
Example 2
4.42g (0.02mol) of benzoxazine P-dampa prepared in example 1 and 9.78g (0.02mol) of pentaerythritol tetra-3-mercaptopropionate are sequentially added into a three-necked flask provided with a magnetic stirring device, a condenser and a thermometer, and the mixture is placed in an oil bath to be slowly heated to 90 ℃ under the conditions of no solvent and nitrogen protection and stirred for reaction for 3 hours to obtain the curing agent I, wherein the structure of the curing agent I is shown as the formula (4), and the yield is 95.8%.
The infrared spectroscopic analysis of the obtained curing agent (i) was carried out, and the results are shown in FIG. 2. As can be seen from the figure, 921cm-1The characteristic peak of the oxazine ring disappears, 3457cm-1An absorption peak with-OH is generated, and the ring opening of the oxazine ring is indicated; and 2569cm-1is-SH stretching vibration peak, 1738cm-1Is C ═ O stretching vibration peak, 1240cm-1And 1047cm-1Is a C-O-C stretching vibration peak, 1154cm-11391cm is a C-N-C stretching vibration peak-1Is in the position of-CH3The peak of vibration of (1). This indicates that the synthesized compound has a correct structure。
Example 3
0.88g (4mmol) of benzoxazine P-dampa prepared in example 1 and 9.78g (0.02mol) of pentaerythritol tetra-3-mercaptopropionate are sequentially added into a three-necked flask provided with a magnetic stirring device, a condenser and a thermometer, and the three-necked flask is placed in an oil bath to slowly raise the temperature to 90 ℃ under the conditions of no solvent and nitrogen protection, stirred and reacted for 3 hours to obtain a curing agent, wherein the structure of the curing agent is shown as a formula (4), and the yield is 98.3%.
The infrared spectroscopic analysis was performed on the prepared curing agent (c), and the result is shown in fig. 3. As can be seen from the figure, 921cm-1The characteristic peak of the oxazine ring disappears, 3466cm-1An absorption peak with-OH is generated, and the ring opening of the oxazine ring is indicated; and 2569cm-1is-SH stretching vibration peak, 1737cm-1Is C ═ O stretching vibration peak, 1240cm-1And 1048cm-1Is a C-O-C stretching vibration peak, 1154cm-11392cm is a C-N-C stretching vibration peak-1Is in the position of-CH3The peak of vibration of (1). This indicates that the synthesized compound has a correct structure.
Example 4
0.44g (2mmol) of benzoxazine P-dampa prepared in example 1 and 9.78g (0.02mol) of pentaerythritol tetra-3-mercaptopropionate are sequentially added into a three-necked flask provided with a magnetic stirring device, a condenser and a thermometer, and the three-necked flask is placed in an oil bath to slowly raise the temperature to 90 ℃ under the conditions of no solvent and nitrogen protection, and stirred for reaction for 3 hours to obtain a curing agent (III), wherein the structure of the curing agent is shown as a formula (4) and the yield is 96.4%.
The infrared spectrum analysis of the prepared curing agent (c) is shown in fig. 4. As can be seen from the figure, 921cm-1The characteristic peak of the oxazine ring disappears, 3468cm-1An absorption peak with-OH is generated, and the ring opening of the oxazine ring is indicated; and 2569cm-1is-SH stretching vibration peak, 1738cm-1Is C ═ O stretching vibration peak, 1239cm-1And 1048cm-1Is a C-O-C stretching vibration peak, 1154cm-11391cm is a C-N-C stretching vibration peak-1Is in the position of-CH3The peak of vibration of (1). This indicates that the synthesized compound has a correct structure.
The curing agents prepared in examples 2,3 and 4 were mixed with epoxy E-44, and the gelation time thereof was measured, and the results are shown in Table 1. As can be seen from the table, the three curing agents all had a short gelation time, and low-temperature curing was achieved. As the proportion of mannich base increases, the curing time decreases dramatically, so the curing time can be adjusted by adjusting the benzoxazine ratio.
TABLE 1
Example 5
18.82g (0.2mol) of phenol, 35.68g (0.44mol) of 37% formaldehyde aqueous solution and 250mL of xylene are sequentially added into a three-mouth bottle provided with a mechanical stirrer, a condenser and a thermometer, and the mixture is put into an oil bath to be slowly heated to 50 ℃; and then adding 39.65g (0.2mol) of 4,4' -diaminodiphenylmethane in three batches at intervals of 15min, wherein the mass fraction of the solute in the system is 32.7%, slowly heating to 85 ℃ after the 4, 4-diaminodiphenylmethane is completely added, stirring for reaction for 5h, washing and drying after the reaction is finished to obtain a light yellow liquid, namely benzoxazine P-ddm, the structure of which is shown in the formula (5), and the yield of which is 95.3%.
Example 6
18.82g (0.2mol) of phenol, 35.68g (0.44mol) of 37% formaldehyde aqueous solution and 200mL of 1, 4-dioxane are sequentially added into a three-neck flask provided with a mechanical stirrer, a condenser and a thermometer, and the three-neck flask is placed in an oil bath to be slowly heated to 55 ℃; then, every 15min, adding 21.63g (0.2mol) of m-phenylenediamine in three batches, wherein the mass fraction of solute in the system is 35.8%, slowly heating to 82 ℃ after the m-phenylenediamine is completely added, stirring for reaction for 5h, washing and drying after the reaction is finished to obtain light yellow liquid, namely benzoxazine P-mpd, the structure of which is shown in formula (6), and the yield is 86.5%.
Example 7
18.82g (0.2mol) of phenol, 35.68g (0.44mol) of 37% formaldehyde aqueous solution and 200mL of dioxane are sequentially added into a three-neck flask provided with a mechanical stirrer, a condenser and a thermometer, and the three-neck flask is placed in an oil bath to be slowly heated to 52 ℃; and then adding 27.238g (0.2mol) of m-xylylenediamine in three batches at intervals of 15min, wherein the mass fraction of the solute in the system is 29.6%, slowly heating to 85 ℃ after the m-xylylenediamine is completely added, stirring for reaction for 5h, and washing and drying after the reaction is finished to obtain a light yellow liquid, namely the benzoxazine P-mxda, the structure of which is shown in the formula (7), and the yield of which is 88.2%.
Example 8
The benzoxazine P-ddm 8.69g (0.02mol) prepared in example 5 and pentaerythritol tetra-3-mercaptopropionate 9.78g (0.02mol) are sequentially added into a three-necked flask provided with a magnetic stirring device, a condenser and a thermometer, and the three-necked flask is placed in an oil bath to slowly raise the temperature to 50 ℃ under the conditions of no solvent and nitrogen protection, and is stirred for reaction for 3 hours to obtain the modified curing agent, wherein the structure of the modified curing agent is shown as the formula (8), and the yield is 97.2%.
Example 9
4.34g (0.01mol) of benzoxazine P-ddm prepared in example 5 and 15.66g (0.02mol) of inositol hexakis (mercaptopropionate) are sequentially added into a three-necked flask provided with a magnetic stirring device, a condenser and a thermometer, and the mixture is placed in an oil bath under the conditions of no solvent and nitrogen protection, slowly heated to 40 ℃ and stirred for reaction for 5 hours to obtain the modified curing agent, wherein the structure of the modified curing agent is shown as the formula (9), and the yield is 98.1%.
Example 10
3.45g (0.01mol) of benzoxazine P-mpd prepared in example 6 and 3.01g (0.02mol) of 1, 6-hexanedithiol are sequentially added into a three-necked flask provided with a magnetic stirring device, a condenser and a thermometer, and the three-necked flask is placed in an oil bath to be slowly heated to 60 ℃ under the conditions of no solvent and nitrogen protection, and stirred for reaction for 4 hours to obtain the modified curing agent, wherein the structure of the modified curing agent is shown as the formula (10), and the yield is 92.3%.
Example 11
The benzoxazine P-mxda 3.725g (0.01mol) prepared in example 7 and 3.01g (0.02mol) of 1, 6-hexanedithiol are sequentially added into a three-necked flask provided with a magnetic stirring device, a condenser and a thermometer, and the three-necked flask is placed in an oil bath to slowly raise the temperature to 80 ℃ under the conditions of no solvent and nitrogen protection, and stirred for 5 hours to react to obtain the modified curing agent, wherein the structure of the modified curing agent is shown in the formula (11), and the yield is 90.8%.
Example 12
The benzoxazine P-mxda 3.725g (0.01mol) prepared in example 7 and pentaerythritol tetra-3-mercaptopropionate 9.78g (0.02mol) are sequentially added into a three-necked flask provided with a magnetic stirring device, a condenser and a thermometer, and the three-necked flask is placed in an oil bath to slowly raise the temperature to 60 ℃ under the conditions of no solvent and nitrogen protection, and stirred for reaction for 4 hours to obtain the modified curing agent, wherein the structure of the modified curing agent is shown as the formula (12), and the yield is 94.9%.
Example 13
3.45g (0.01mol) of benzoxazine P-mpd prepared in example 6 and 9.78g (0.02mol) of pentaerythritol tetra-3-mercaptopropionate are sequentially added into a three-necked flask provided with a magnetic stirring device, a condenser and a thermometer, and the mixture is placed in an oil bath to be slowly heated to 50 ℃ under the conditions of no solvent and nitrogen protection, and stirred for reaction for 4 hours to obtain the modified curing agent, wherein the structure of the modified curing agent is shown as the formula (13), and the yield is 91.1%.
Example 14
The benzoxazine P-mxda 3.725g (0.01mol) prepared in example 7 and the inositol hexakis (mercaptopropionate) 15.66g (0.02mol) are sequentially added into a three-necked flask provided with a magnetic stirring device, a condenser and a thermometer, and placed in an oil bath under the conditions of no solvent and nitrogen protection, the temperature is slowly raised to 40 ℃, and the modified curing agent is obtained after stirring reaction for 5 hours, wherein the structure of the modified curing agent is shown as a formula (14), and the yield is 92.2%.
Example 15
9.41g (0.1mol) of phenol, 22.83g (0.1mol) of bisphenol A, 19.8g (0.66mol) of paraformaldehyde and 300mL of toluene are sequentially added into a three-necked bottle provided with a mechanical stirrer, a condenser and a thermometer, 29.14g (0.3mol) of furfurylamine is added, the temperature is increased to 90 ℃, stirring reaction is carried out for 5 hours, and washing and drying are carried out after the reaction is finished to obtain yellow liquid, namely benzoxazine P-BA-fa, wherein the yield is 89.2%.
Example 16
28.23g (0.3mol) of phenol, 19.8g (0.66mol) of paraformaldehyde and 300mL of toluene are sequentially added into a three-necked bottle provided with a mechanical stirrer, a condenser and a thermometer, 19.83g (0.1mol) of 4,4' -diaminodiphenylmethane and 9.31g (0.1mol) of aniline are added, the temperature is raised to 90 ℃, the stirring reaction is carried out for 5 hours, and after the reaction is finished, washing and drying are carried out to obtain light yellow liquid, namely benzoxazine P-a-ddm, wherein the yield is 86.7%.
Example 17
Benzoxazine P-BA-fa (0.02mol) prepared in example 15 and pentaerythritol tetra-3-mercaptopropionate (0.02mol) were added in sequence into a three-necked flask equipped with a magnetic stirrer, a condenser and a thermometer, and placed in an oil bath under the conditions of no solvent and nitrogen protection and slowly heated to 30 ℃ to be stirred and reacted for 15 hours to obtain the modified curing agent with the yield of 85.5%.
Example 18
Benzoxazine P-a-ddm (0.02mol) prepared in example 16 and pentaerythritol tetra-3-mercaptopropionate (0.02mol) were sequentially added into a three-necked flask equipped with a magnetic stirrer, a condenser and a thermometer, and placed in an oil bath under the conditions of no solvent and nitrogen protection to slowly raise the temperature to 40 ℃ for stirring reaction for 12 hours to obtain a modified curing agent with a yield of 81.9%.
Example 19
Benzoxazine P-ddm (0.02mol), pentaerythritol tetra-3-mercaptopropionate (0.01mol) and 1, 6-hexanedithiol (0.01mol) prepared in example 5 were added in sequence into a three-necked flask equipped with a magnetic stirrer, a condenser and a thermometer, and placed in an oil bath under the conditions of no solvent and nitrogen protection to slowly raise the temperature to 40 ℃ and stirred for reaction for 10 hours to obtain a modified curing agent with a yield of 86.3%.
Example 20
Benzoxazine P-BA-fa (0.02mol) prepared in example 15, pentaerythritol tetra-3-mercaptopropionate (0.01mol) and 1, 6-hexanedithiol (0.01mol) were added in sequence in a three-necked flask equipped with a magnetic stirrer, a condenser and a thermometer, and placed in an oil bath under the conditions of no solvent and nitrogen protection to slowly raise the temperature to 50 ℃ and stirred for reaction for 8 hours to obtain a modified curing agent with a yield of 84.3%.
Through further verification of products of examples 8-14 and 17-20, the result shows that the gelation time of the obtained benzoxazine modified amine curing agent is within the range of 15 s-100 s at 50 ℃; the gelation time is within the range of 28 s-150 s at the temperature of 40 ℃; the gelation time is in the range of 50s to 250s at 30 ℃.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included therein.