Epoxy resin curing agent and preparation method thereof, and epoxy adhesive

Abstract

The present invention relates to the field of curing agents, and more specifically, the present invention relates to an epoxy resin curing agent and a preparation method thereof, and an epoxy adhesive. The method comprises: mixing a thiol compound solution and a catalyst, dripping a vinyl compound solution, reacting at 30 to 100° C. for 15 to 25 hours, and performing reduced pressure distillation to obtain the epoxy resin curing agent. The present invention provides a novel epoxy curing agent, wherein the vinyl compound provided by the present invention and the thiol compound undergo an addition reaction, and the thiol compound is chain extended to obtain a polythiol epoxy curing agent, which has a high viscosity epoxy resin curing agent and improves the yield of the curing agent. The inventors have found that the epoxy resin curing agent prepared by the preparation method provided by the present invention can be used for the rapid curing of epoxy resins. While avoiding glue overflow, the cured adhesive product has high adhesion and heat resistance, and has no irritating odor, which can improve the convenience of use and expand the field of application.

Description

Technical Field

[0001] The present invention relates to the field of curing agents, and more specifically, to an epoxy resin curing agent and a preparation method thereof, and an epoxy adhesive. Background Art

[0002] In the application of epoxy resin, curing agent plays a very important role. There are many types of epoxy resin curing agents. The most widely used room temperature curing agent is amine curing agent. The biggest disadvantage of amine curing agent is that the curing speed is too slow at room temperature and low temperature. It takes a day to cure at room temperature of 25℃, which cannot meet the requirements of fast curing at room temperature or low temperature. However, thiol curing agent can quickly cure epoxy resin at room temperature and low temperature, which has great advantages in outdoor work places in winter, which is unmatched by other curing agents.

[0003] Polythiol is a very important room temperature curing agent for epoxy resin. The biggest advantage of its curing system is that it can cure quickly at room temperature and low temperature. Commonly used thiol curing agents include pentaerythritol tetrakis(3-mercaptopropionic acid), pentaerythritol tetrakismercaptoacetic acid, tris(3-mercaptopropionic acid) trimethylolpropane ester, and tris(2-mercaptoacetic acid) trimethylolpropane ester. Epoxy resin can be cured at room temperature under the catalysis of tertiary amine accelerators. However, the current thiol curing agents have the following shortcomings: First, thiol curing agents generally have a strong pungent odor; second, thiol curing agents have a low viscosity and are very easy to flow to places where they should not flow during use, causing glue overflow, which causes inconvenience to daily use and construction; in addition, the product after curing of thiol curing agents and epoxy resins has poor heat resistance and general bonding strength, which cannot meet the use requirements in certain fields and environments.

[0004] At present, the synthesis of new thiol curing agents is mainly carried out by reacting compounds containing vinyl groups with small molecular thiol curing agents. Generally, when thiol and vinyl compounds react, due to the presence of polythiol groups in thiol, multiple vinyl compounds may be connected, and the two vinyl structures in the vinyl compound may be connected to different thiols, resulting in a macromolecular mixture of cross-arranged thiol compounds and thiols, which is easy to generate gel during the reaction. In order to avoid this situation, two methods are generally used, one is to add inhibitors, and the other is to reduce the temperature and reaction time, but this may increase costs, or the yield and viscosity of the product are low, resulting in glue overflow, poor adhesion and heat resistance during subsequent construction. Summary of the invention

[0005] In order to solve the above problems, the first aspect of the present invention provides a method for preparing an epoxy resin curing agent, comprising: mixing a thiol compound solution and a catalyst, adding a vinyl compound solution dropwise, reacting at 30 to 100° C. for 15 to 25 hours, and distilling under reduced pressure to obtain the epoxy resin curing agent.

[0006] As a preferred technical solution of the present invention, the structural formula of the thiol compound is as shown in formula (1) or formula (2):

[0007]

[0008] n is 1 or 2, and R is H or Me.

[0009] As a preferred technical solution of the present invention, the structural formula of the vinyl compound is shown in formula (3):

[0010]

[0011] R" is H or Me, and R' is selected from one or more of an alkyl group, a chain ether group, and a cyclic ether group.

[0012] As a preferred technical solution of the present invention, the structural formula of the alkyl group is shown in formula (4):

[0013]

[0014] R1 is H or Me, and n1 is 1-30.

[0015] As a preferred technical solution of the present invention, the structural formula of the chain ether group is as shown in formula (5), (6) or (7):

[0016]

[0017] R2 is H or Me, n2 is 1 to 30;

[0018]

[0019] n3 is 1 to 30;

[0020]

[0021] n4 is 1 to 30.

[0022] As a preferred technical solution of the present invention, the structural formula of the cyclic ether group is shown in formula (8):

[0023]

[0024] R3 is H or Me, n5 is 1-30, and n6 is 1-3.

[0025] As a preferred technical solution of the present invention, the molar ratio of the thiol compound to the vinyl compound is (1.8-2.2):1.

[0026] As a preferred technical solution of the present invention, the solvent of the thiol compound solution is selected from one or more of halogenated alkanes, ketone solvents, and ester solvents, and the solvent of the vinyl compound solution is selected from one or more of halogenated alkanes, ketone solvents, and ester solvents.

[0027] The second aspect of the present invention provides an epoxy resin curing agent, which is prepared according to the preparation method of the epoxy resin curing agent as described above.

[0028] A third aspect of the present invention provides an epoxy adhesive, wherein the raw materials for preparing the adhesive include the epoxy resin curing agent as described above, and an epoxy resin.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention provides a novel epoxy curing agent, wherein the vinyl compound provided by the present invention and the thiol compound undergo an addition reaction, the thiol compound is chain extended, and a polythiol epoxy curing agent is obtained with a high yield.

[0031] (2) The inventors unexpectedly discovered that the present invention uses a thiol compound with multiple thiol groups to react with a vinyl compound. By using a vinyl compound with a suitable structure, especially a vinyl compound with a chain ether structure, and controlling a suitable molar ratio, the reactivity of the thiol compound and the vinyl compound can be controlled, the occurrence of the gel reaction can be reduced, and the reaction can be carried out at a suitable temperature for a long time, thereby obtaining an epoxy resin curing agent with a higher viscosity and improving the yield of the curing agent.

[0032] (3) In addition, the inventors have found that the reaction solvent and heating, such as the temperature of oil bath heating, also play an important role in the reaction system. The present invention adopts an oil bath heating temperature of 30 to 100°C, especially 75 to 85°C, and adopts a halogenated alkane with a relatively low boiling point and volatility, such as chloroform with a boiling point of 61.2°C. On the one hand, the mercapto compound and the vinyl compound are reacted under reflux, and on the other hand, the higher heating temperature also causes the reaction system to heat up locally, thereby promoting the improvement of the later yield while avoiding the formation of gel, thereby obtaining a high viscosity and transparent epoxy resin curing agent.

[0033] (4) The inventors have found that the epoxy resin curing agent prepared by the preparation method provided by the present invention can be used for the rapid curing of epoxy resin. While avoiding glue overflow, the cured adhesive product has high adhesion and heat resistance and no irritating odor, which can improve the convenience of use and expand the field of application. DETAILED DESCRIPTION

[0034] The content of the present invention can be more easily understood by selecting the following detailed description of the preferred implementation method of the present invention and the embodiments included. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art to which the present invention belongs. When there is a conflict, the definition in this specification shall prevail.

[0035] As used herein, the term "prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0036] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0037] When amount, concentration or other value or parameter is expressed as range, preferred range or a series of upper preferred value and lower preferred value limit range, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value and any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when disclosing range "1 to 5", described range should be interpreted as including range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc. When numerical range is described in this article, unless otherwise stated, the range is intended to include its end value and all integers and fractions within the range.

[0038] Singular forms include plural references unless the context clearly indicates otherwise. "Optional" or "either" means that the subsequently described event or incident may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

[0039] Approximate terms in the specification and claims are used to modify quantities, indicating that the present invention is not limited to the specific quantity, but also includes acceptable and modified parts close to the quantity without causing changes in the relevant basic functions. Accordingly, the use of "about", "approximately", etc. to modify a numerical value means that the present invention is not limited to the exact numerical value. In some examples, the approximate terms may correspond to the accuracy of the instrument for measuring the numerical value. In the specification and claims of this application, range limitations can be combined and / or interchanged, and if not otherwise stated, these ranges include all subranges contained therein.

[0040] In addition, the indefinite articles "a" and "an" before the elements or components of the present invention have no restrictions on the quantity requirements (i.e. the number of occurrences) of the elements or components. Therefore, "a" or "an" should be interpreted as including one or at least one, and the elements or components in the singular form also include the plural form, unless the number is obviously intended to be in the singular form.

[0041] The present invention is described below by specific implementation methods, but is not limited to the specific embodiments given below.

[0042] The first aspect of the present invention provides a method for preparing an epoxy resin curing agent, comprising: mixing a thiol compound solution and a catalyst, adding a vinyl compound solution dropwise, reacting at 30-100° C. for 15-25 hours, and performing reduced pressure distillation to obtain the epoxy resin curing agent.

[0043] In a preferred embodiment, the temperature of the reaction of the present invention is 30-100° C., preferably 65-90° C., more preferably 75-85° C. The temperature of the reaction of the present invention is the temperature of the heating medium outside the reaction container during the reaction. For example, when an oil bath is used for heating, the reflected temperature is the temperature of the oil bath.

[0044] In a preferred embodiment, the reaction time of the present invention is 15 to 25 hours, and examples include 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, and 25 hours.

[0045] Thiol compounds

[0046] In one embodiment, the structural formula of the thiol compound of the present invention is as shown in formula (1) or formula (2):

[0047]

[0048] n is 1 or 2, R is H or Me, and examples thereof include:

[0049] Vinyl compounds

[0050] In one embodiment, the structural formula of the vinyl compound of the present invention is shown in formula (3):

[0051]

[0052] R" is H or Me, and R' is selected from one or more of an alkyl group, a chain ether group, and a cyclic ether group.

[0053] Preferably, the structural formula of the alkyl group of the present invention is as shown in formula (4):

[0054]

[0055] R1 is H or Me, n1 is 1 to 30, preferably 1 to 20, more preferably 1 to 10, and examples thereof include 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0056] More preferably, the structural formula of the chain ether group of the present invention is as shown in formula (5), (6) or (7):

[0057]

[0058] R2 is H or Me, n2 is 1-30, preferably 1-20, more preferably 1-10, and the examples include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10; the examples include, Polyethylene glycol 400 diacrylate (CAS No.: 26570-48-9);

[0059]

[0060] n3 is 1 to 30, preferably 1 to 20, more preferably 1 to 10, and examples thereof include 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10;

[0061]

[0062] n4 is 1 to 30, preferably 1 to 20, more preferably 1 to 10, and examples thereof include 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0063] More preferably, the structural formula of the cyclic ether group of the present invention is as shown in formula (8):

[0064]

[0065] R3 is H or Me, n3 is 1 to 30, preferably 1 to 20, more preferably 1 to 10, and examples thereof include 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10, and n6=1 to 3, and examples thereof include 1, 2, and 3. It is a benzene ring or an aliphatic ring, such as phenyl, cyclohexyl, cyclopentyl, and cyclodecyl.

[0066] More preferably, the molar ratio of the mercapto compound to the vinyl compound of the present invention is (1.8-2.2):1, including 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, and preferably 1.8-2.15:1.

[0067] In a preferred embodiment, the solvent of the thiol compound solution of the present invention is selected from one or more of halogenated alkanes, ketone solvents, and ester solvents, and the solvent of the vinyl compound solution is selected from one or more of halogenated alkanes, ketone solvents, and ester solvents.

[0068] Examples of halogenated alkanes include methyl chloride, dichloromethane, and chloroform; examples of ketone solvents include acetone, methyl ethyl ketone, and methyl ethyl ketone; examples of ester solvents include ethyl acetate, propyl acetate, and butyl acetate. Preferably, the halogenated alkanes are used, and more preferably, chloroform is used.

[0069] catalyst

[0070] The present invention does not specifically limit the catalyst, and examples thereof include amine catalysts such as N,N-dimethylbenzylamine, triethylamine, triethanolamine, tripropylamine, tributylamine, and diethylisobutanolamine.

[0071] The second aspect of the present invention provides an epoxy resin curing agent, which is prepared according to the preparation method of the epoxy resin curing agent as described above.

[0072] The third aspect of the present invention provides an epoxy adhesive, wherein the raw materials for preparing the adhesive include the epoxy resin curing agent as described above, and the epoxy resin. The raw materials for preparing the adhesive of the present invention also include one or more of a photoinitiator, an antioxidant, an ultraviolet absorber, etc., without specific limitation.

[0073] Example

[0074] The present invention is described in detail below by way of examples. It is necessary to point out here that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by professionals and technicians in this field based on the content of the present invention above still belong to the scope of protection of the present invention.

[0075] Embodiments 1 to 8 provide an epoxy resin curing agent and a preparation method thereof

[0076] Example 1

[0077] This example provides a method for preparing an epoxy resin curing agent, comprising: adding a 122g chloroform solution of a thiol compound and 0.3g triethylamine catalyst into a three-necked flask under nitrogen, dripping a 25g chloroform solution of a vinyl compound dropwise, mechanically stirring, reacting at 80°C for 16h, collecting the reaction product, and distilling under reduced pressure to obtain 140g of a viscous light yellow transparent product after the solvent is evaporated, with a yield of 95.2%.

[0078] The structural formula of the thiol compound is:

[0079]

[0080] The structural formula of the vinyl compound is:

[0081]

[0082] This example also provides an epoxy resin curing agent prepared by the preparation method described above.

[0083] Example 2

[0084] This example provides a method for preparing an epoxy resin curing agent, comprising: adding a 122g chloroform solution of a thiol compound and 0.34g N,N-dimethylbenzylamine catalyst into a three-necked flask under nitrogen, dripping a 35g chloroform solution of a vinyl compound dropwise, mechanically stirring, reacting at 80°C for 20h, collecting the reaction product, and distilling under reduced pressure to obtain 142g of a viscous light yellow transparent product after the solvent is evaporated, with a yield of 90.4%.

[0085] The structural formula of the thiol compound is:

[0086]

[0087] The structural formula of the vinyl compound is:

[0088]

[0089] This example also provides an epoxy resin curing agent prepared by the preparation method described above.

[0090] Example 3

[0091] This example provides a method for preparing an epoxy resin curing agent, comprising: adding a 122g chloroform solution of a thiol compound and 0.3g triethylamine catalyst into a three-necked flask under nitrogen, dripping a 63g chloroform solution of a vinyl compound dropwise, mechanically stirring, reacting at 80°C for 20h, collecting the reaction product, and distilling under reduced pressure to obtain 170g of a viscous light yellow transparent product after the solvent is evaporated, with a yield of 91.5%.

[0092] The structural formula of the thiol compound is:

[0093]

[0094] The vinyl compound is polyethylene glycol 400 diacrylate.

[0095] This example also provides an epoxy resin curing agent prepared by the preparation method described above.

[0096] Example 4

[0097] This example provides a method for preparing an epoxy resin curing agent, comprising: adding a 108g chloroform solution of a thiol compound and 0.4g DBU catalyst into a three-necked flask under nitrogen, dripping a 63g chloroform solution of a vinyl compound dropwise, mechanically stirring, reacting at 80°C for 20h, collecting the reaction product, and distilling under reduced pressure to obtain 156g of a viscous light yellow transparent product after the solvent is evaporated, with a yield of 91.2%.

[0098] The structural formula of the thiol compound is:

[0099]

[0100] The vinyl compound is polyethylene glycol 400 diacrylate.

[0101] This example also provides an epoxy resin curing agent prepared by the preparation method described above.

[0102] Example 5

[0103] This example provides a method for preparing an epoxy resin curing agent, comprising: adding a 108g chloroform solution of a thiol compound and 0.3g triethylamine catalyst into a three-necked flask under nitrogen, dripping a 25g chloroform solution of a vinyl compound dropwise, mechanically stirring, reacting at 80°C for 20h, collecting the reaction product, and distilling under reduced pressure to obtain 156g of a viscous light yellow transparent product after the solvent is evaporated, with a yield of 91.2%.

[0104] The structural formula of the thiol compound is:

[0105]

[0106] The structural formula of the vinyl compound is:

[0107]

[0108] This example also provides an epoxy resin curing agent prepared by the preparation method described above.

[0109] Example 6

[0110] This example provides a method for preparing an epoxy resin curing agent, comprising: adding a 99g chloroform solution of a thiol compound and 0.3g triethylamine catalyst into a three-necked flask under nitrogen, dripping a 25g chloroform solution of a vinyl compound dropwise, mechanically stirring, reacting at 80°C for 20h, collecting the reaction product, and distilling under reduced pressure to obtain 120g of a viscous light yellow transparent product after the solvent is evaporated, with a yield of 96.8%.

[0111] The structural formula of the thiol compound is:

[0112]

[0113] The structural formula of the vinyl compound is:

[0114]

[0115] This example also provides an epoxy resin curing agent prepared by the preparation method described above.

[0116] Example 7

[0117] This example provides a method for preparing an epoxy resin curing agent, comprising: adding 89g of a thiol compound-chloroform solution and 0.3g of a triethylamine catalyst into a three-necked flask under nitrogen, dripping 37g of a vinyl compound-chloroform solution dropwise, mechanically stirring, reacting at 80°C for 20h, collecting the reaction product, and distilling under reduced pressure to obtain 120g of a viscous light yellow transparent product after the solvent is evaporated, with a yield of 95.2%.

[0118] The structural formula of the thiol compound is:

[0119]

[0120] The structural formula of the vinyl compound is:

[0121]

[0122] This example also provides an epoxy resin curing agent prepared by the preparation method described above.

[0123] Example 8

[0124] This example provides a method for preparing an epoxy resin curing agent, comprising: adding 89g of a thiol compound-chloroform solution and 0.3g of a triethylamine catalyst into a three-necked flask under nitrogen, dripping 63g of a vinyl compound-chloroform solution dropwise, mechanically stirring, reacting at 80°C for 20h, collecting the reaction product, and distilling under reduced pressure to obtain 140g of a viscous light yellow transparent product after the solvent is evaporated, with a yield of 92.1%.

[0125] The structural formula of the thiol compound is:

[0126]

[0127] The vinyl compound is polyethylene glycol 400 diacrylate.

[0128] This example also provides an epoxy resin curing agent prepared by the preparation method described above.

[0129] Embodiments 9 to 16 provide an epoxy adhesive comprising the epoxy resin curing agent of embodiments 1 to 8

[0130] Examples 9 to 16 provide an epoxy adhesive, and the raw materials for preparing the epoxy adhesive are shown in Table 1 in parts by weight.

[0131] Table 1

[0132]

[0133] Performance Evaluation

[0134] 1. Gel time: Take 0.5g of component A and 0.5g of component B on a polytetrafluoroethylene plate, start timing with a stopwatch, and quickly stir with a glass rod. When the viscosity of the mixed liquid begins to increase, start drawing wires. When the wires cannot be drawn, press the stopwatch and record the gel time of the resin. Measure three times and take the average value.

[0135] 2. Shear strength: Tested according to GB / 7124-86, the material is 120×20×2.5 (mm) A3 iron sheet, the overlap length is 10mm, the surface is polished with sandpaper, and the test is carried out at room temperature. Epoxy resin and curing agent are mixed in a ratio of 1:1 and coated on the iron sheet, then the iron sheets are overlapped, cured at 25℃ for 24 hours, and tensile test is carried out on Zwick / Roll universal testing machine to obtain the maximum tensile force P max . Test temperature: 25℃, tensile speed: 10mm / min.

[0136] Shear strength τ = P max / S, S refers to the bonding area.

[0137] 3. Thermal stability test: The samples provided in the examples were tested using a thermal gravimetric analyzer (TGA), and the temperature at which the weight loss was 5% was as shown in Table 2.

[0138] Table 2 Performance characterization test

[0139] Example Gel time (min) Shear strength(MPa) TGA (5% td, ℃) Example 9 7.2 7.4 325 Example 10 7.3 7.5 322 Embodiment 11 7.5 7.0 324 Example 12 7.4 7.4 328 Embodiment 13 6.8 7.4 326 Embodiment 14 7.8 7.6 326 Embodiment 15 7.8 7.8 330 Example 16 8.0 7.6 327

[0140] It can be seen from the test results that a transparent curing agent with higher viscosity can be obtained by the method provided by the present invention, no gel is produced during the reaction process, and the yield is high. The curing agent provided by the present invention can be used for the rapid curing of epoxy resin, has no irritating odor and glue overflow, is easy to use, and has good adhesion and heat resistance.

[0141] The foregoing examples are merely illustrative and are used to explain some features of the method of the present invention. The appended claims are intended to claim the widest possible range that can be conceived, and the embodiments presented herein are only illustrations of selected implementations according to the combination of all possible embodiments. Therefore, it is the applicant's intention that the appended claims are not limited by the selection of examples that illustrate the features of the present invention. Some numerical ranges used in the claims also include sub-ranges within them, and changes in these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A method for preparing an epoxy resin curing agent, characterized in that: include: The thiol compound solution and the catalyst are mixed, the vinyl compound solution is added dropwise, the mixture is reacted at 30 to 100° C. for 15 to 25 hours, and the mixture is distilled under reduced pressure to obtain the epoxy resin curing agent; The structural formula of the thiol compound is shown in formula (1) or formula (2): n is 1 or 2, R is H or Me; The structural formula of the vinyl compound is shown in formula (3): R" is H or Me, and R' is selected from a chain ether group; The structural formula of the chain ether group is shown in formula (5), (6) or (7): R2 is H or Me, n2 is 1 to 30; n3 is 1 to 30; n4 is 1 to 30; The molar ratio of the mercapto compound to the vinyl compound is (1.8-2.2):

1.

2. The method for preparing an epoxy resin curing agent according to claim 1, characterized in that: The solvent of the thiol compound solution is selected from one or more of halogenated alkanes, ketone solvents, and ester solvents, and the solvent of the vinyl compound solution is selected from one or more of halogenated alkanes, ketone solvents, and ester solvents.

3. An epoxy resin curing agent, characterized in that The epoxy resin curing agent is prepared according to the preparation method of any one of claims 1 to 2.

4. An epoxy adhesive, characterized in that: The raw materials for preparing the adhesive include the epoxy resin curing agent according to claim 3 and epoxy resin.

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