Normal-temperature rapid curing agent, synthesis method and application

Abstract

The invention belongs to the technical field of curing agent preparation, and particularly relates to a normal-temperature rapid curing agent, a synthesis method and application. Tetraethylenepentamine is modified through thiourea, thiourea groups are introduced while the excellent performance of tetraethylenepentamine is reserved, the curing rate of tetraethylenepentamine at the normal temperature can be greatly increased, and the irritation of tetraethylenepentamine is reduced. The prepared modified amine curing agent is simple in preparation process, high in operability and beneficial to industrialization, no solvent is used, no pungent smell exists, and the environment-friendly requirement is met; the prepared adhesive is high in curing rate at normal temperature, high in bonding strength and good in mechanical property.

Description

Technical Field

[0001] The invention belongs to the technical field of curing agent preparation, and particularly relates to a preparation method and application of a modified amine curing agent that cures quickly at room temperature. Background Art

[0002] Amine compounds, as curing agents for epoxy resins, primarily react with the epoxy groups in the epoxy resin through a ring-opening addition reaction to form a crosslinked structure. Depending on the type of amine compound, they can be categorized as aliphatic amines, alicyclic amines, aromatic amines, and polyetheramines. Aliphatic amines, such as tetraethylenepentamine, contain multiple unhindered amine groups within their molecules. These compounds efficiently crosslink with the epoxy groups in the epoxy resin to form a dense, three-dimensional network. The cured material exhibits excellent mechanical strength, solvent resistance, and abrasion resistance.

[0003] While it can undergo a curing and crosslinking reaction with epoxy resin at room temperature, the reaction time is relatively long. Generally, the curing time with epoxy resin at room temperature is over 24 hours, and the degree of cure is low. Furthermore, unmodified tetraethylenepentamine is highly corrosive, and skin contact or inhalation can cause a range of health problems. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a method for preparing a modified amine curing agent that cures rapidly at room temperature and its application in view of the shortcomings of the prior art.

[0005] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are as follows:

[0006] The first technical purpose of the present invention is to provide a method for synthesizing a room-temperature fast curing agent, comprising mixing thiourea and polyethylene polyamine, passing argon gas for protection and exhausting the air, stirring and uniformly heating, and then reacting at a temperature of 110-140°C for 2.5-4h to prepare a modified amine curing agent.

[0007] Preferably, the polyethylene polyamine is one or more combinations of diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

[0008] Furthermore, the molar ratio of thiourea to polyethylene polyamine is 1:1.

[0009] Specifically, in the above-mentioned synthesis method of the room temperature fast curing agent, the amounts of the reactants are as follows:

[0010] Thiourea 1-5 mol;

[0011] Diethylenetriamine 1-5 mol;

[0012] Triethylenetetramine 1-5 mol;

[0013] 1~5 mol of tetraethylenepentamine.

[0014] It should be noted that, through a large number of experimental screenings, the present invention modifies tetraethylenepentamine by thiourea, thereby introducing thiourea groups while retaining the excellent properties of tetraethylenepentamine itself, which can greatly improve its curing rate at room temperature and reduce the irritation of tetraethylenepentamine itself.

[0015] The second technical purpose of the present invention is to provide a room temperature fast curing agent synthesized by the method as described above, wherein the room temperature fast curing agent is a modified amine curing agent.

[0016] The third technical purpose of the present invention is to provide a use of a room temperature fast curing agent synthesized by the method described above in epoxy resin adhesives.

[0017] Preferably, the synthesized curing agent is added to the epoxy resin adhesive system, and the composition, in parts by weight, comprises:

[0018] Epoxy resin 016430-90 parts;

[0019] 5-20 parts of modified amine curing agent;

[0020] Filler 0-70 parts;

[0021] Active diluent 0-10 parts;

[0022] Toughening agent 0-10 parts.

[0023] It is worth noting that the present invention uses epoxy resin as the base resin to provide excellent bonding performance for the adhesive system; the modified amine curing agent has a greatly improved curing speed compared to the unmodified one and has no irritating odor; the performance is improved and the cost of the composition is reduced by adding inorganic fillers; the viscosity of the adhesive system is reduced and the performance is improved by adding active diluents; and the bonding performance of the adhesive is improved by adding liquid rubber toughening agents.

[0024] Furthermore, the adhesive system includes: 40-70 parts of epoxy resin 0164; 10-20 parts of modified amine curing agent; 0-40 parts of filler; 1-5 parts of active diluent; and 2-10 parts of toughening agent.

[0025] Preferably, the reactive diluent not only performs the solvent function to reduce viscosity but also contains reactive epoxy groups; more preferably, the diluent is a compound having two epoxy groups in one molecule.

[0026] From the viewpoint of reducing the viscosity of the resulting epoxy resin composition, the viscosity of the reactive diluent component is preferably 1 to 100 mPa·s, more preferably 1 to 20 mPa·s.

[0027] Specifically, the active diluent is one or a mixture of allyl glycidyl ether, n-butyl glycidyl ether, phenyl glycidyl ether, methacrylic acid glycidyl ether, diglycidyl ether, polyethylene glycol bisglycidyl ether, polypropylene glycol bisglycidyl ether, and 1,4-butanediol diglycidyl ether.

[0028] Preferably, the toughening agent is liquid rubber, which enhances the toughness of the adhesive system by reacting with the epoxy resin; more preferably, the toughening agent is a compound having a terminal epoxy group.

[0029] Specifically, the toughening agent is one or a mixture of carboxyl-terminated liquid nitrile rubber CTBN, amino-terminated liquid nitrile rubber ATBN, hydroxyl-terminated liquid nitrile rubber HTBN, and epoxy-terminated liquid nitrile rubber ETBN.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1) The modified amine curing agent prepared by the present invention has a simple preparation process, strong operability, is conducive to industrialization, does not use solvents, has no irritating odor, and meets environmental protection requirements;

[0032] 2) The adhesive prepared by the present invention has a fast curing rate at room temperature, high bonding strength and good mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0034] Figure 1 This is the mechanism of thiourea modification of linear fatty amines.

[0035] Figure 2 Schematic diagram of the synthesis process.

[0036] Figure 3 It is a rapid curing application process at room temperature.

[0037] Figure 4 It is the structural formula of modified amine curing agent. DETAILED DESCRIPTION

[0038] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] The term "embodiment" is used herein specifically to describe any embodiment as "exemplary," and should not be construed as superior or preferable to other embodiments. Performance indicators in the embodiments of this application were tested using conventional testing methods in the art, unless otherwise specified. It should be understood that the terms used in this application are intended solely to describe specific implementations and are not intended to limit the disclosure herein.

[0040] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0041] In order to better illustrate the content of this application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that this application can be implemented without certain specific details. In the examples, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of this application.

[0042] Under the premise of no conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of this application.

[0043] The invention discloses a preparation method and application of a modified amine curing agent capable of rapid curing at room temperature. Although unmodified polyethylene polyamine can cure epoxy resin at room temperature, the curing time is still more than 24 hours and the agent itself is irritating. However, unmodified polyethylene polyamine is modified using thiourea in a one-step method. The one-step method is simple and convenient and is used to improve performance in terms of room-temperature curing efficiency, reactivity, irritation, etc. The curing rate of the modified curing agent is greatly improved. This is because the C=S group exhibits higher reactivity, while compounds having the C=S group are less stable. In addition, the introduction of the -SH group can significantly increase the curing speed of the amine curing agent, improve the brittleness of the curing agent, reduce its toxicity, rapidly cure at room temperature, and achieve strong mechanical properties, thereby achieving a better curing effect.

[0044] At the same time, the present invention also provides several adhesive formulations using the modified amine curing agent and the anti-shearing properties of the adhesive after rapid curing at room temperature.

[0045] For a better understanding of the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as limiting the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above invention content are also considered to fall within the scope of protection of the present invention.

[0046] Example 1

[0047] 1. A method for preparing a thiourea-modified modified amine curing agent, comprising the following steps:

[0048] 0.15 mol of diethylenetriamine and 0.1 mol of thiourea were added to a three-necked flask, and argon was passed through for 5 minutes to expel the air in the flask. Under argon protection, the temperature was raised to 130°C and maintained for 3 hours. The temperature was then slowly lowered to 50-60°C and then to room temperature to obtain thiourea-modified diethylenetriamine curing agent 1.

[0049] 2. Performance test of finished curing agent 1

[0050] 0164 epoxy resin (Nantong Xingchen Synthetic Materials Co., Ltd.) and the finished curing agent 1 prepared in the present invention were mixed and stirred evenly in a mass ratio of 100:20, and then evenly coated on a stainless steel plate. The measured properties were as follows:

[0051] At 25°C, the gel time is 24 minutes and the surface dry time is 87 minutes;

[0052] 0164 epoxy resin (Nantong Xingchen Synthetic Materials Co., Ltd.) and unmodified diethylenetriamine were mixed and stirred at a mass ratio of 100:20, and then evenly coated on a stainless steel plate. The measured properties are as follows:

[0053] The gel time at 25°C is 72 minutes and the surface dry time is 132 minutes.

[0054] Example 2

[0055] 1. A method for preparing a thiourea-modified modified amine curing agent, comprising the following steps:

[0056] 0.14 mol of triethylenetetramine and 0.1 mol of thiourea were added to a three-necked flask, and argon was passed through for 5 minutes to expel the air in the flask. Under argon protection, the temperature was raised to 140°C and maintained for 3 hours. The temperature was then slowly lowered to 50-60°C and then to room temperature to obtain thiourea-modified triethylenetetramine curing agent 2.

[0057] 2. Performance test of finished curing agent 2

[0058] 0164 epoxy resin (Nantong Xingchen Synthetic Materials Co., Ltd.) and the finished curing agent 2 prepared in the present invention were mixed and stirred evenly in a mass ratio of 100:20, and then evenly coated on a stainless steel plate. The measured properties were as follows:

[0059] At 25°C, the gel time is 23 minutes and the surface dry time is 86 minutes;

[0060] 0164 epoxy resin (Nantong Xingchen Synthetic Materials Co., Ltd.) and unmodified triethylenetetramine were mixed and stirred at a mass ratio of 100:20, and then evenly coated on a stainless steel plate. The measured properties were as follows:

[0061] The gel time at 25°C is 91 minutes and the surface dry time is 157 minutes.

[0062] Example 3

[0063] 1. A method for preparing a thiourea-modified modified amine curing agent, comprising the following steps:

[0064] To a three-necked flask, add 0.14 mol of tetraethylene pentamine and 0.1 mol of thiourea, and pass argon for 5 minutes to expel the air in the flask. Under argon protection, stir, raise the temperature to 130°C, and maintain it for 3 hours. Then, slowly cool it to 50-60°C, and then to room temperature to obtain thiourea-modified tetraethylene pentamine curing agent 3.

[0065] 2. Performance test of finished curing agent 3

[0066] 0164 epoxy resin (Nantong Xingchen Synthetic Materials Co., Ltd.) and the finished curing agent 3 prepared in the present invention were mixed and stirred evenly in a mass ratio of 100:20, and then evenly coated on a stainless steel plate. The measured properties were as follows:

[0067] At 25°C, the gel time is 24 minutes and the surface dry time is 96 minutes;

[0068] 0164 epoxy resin (Nantong Xingchen Synthetic Materials Co., Ltd.) and unmodified tetraethylene pentamine were mixed and stirred at a mass ratio of 100:20, and then evenly coated on a stainless steel plate. The measured properties were as follows:

[0069] The gel time at 25°C is 72 minutes and the surface dry time is 153 minutes.

[0070] Table 1

[0071]

[0072] The raw materials used in the following examples and comparative examples are as follows:

[0073] Epoxy resin

[0074] Nantong Xingchen Synthetic Materials Co., Ltd. produces 0164, with an epoxy equivalent of 186-190g / eq.

[0075]

Modified amine curing agent

[0076] A1: Homemade, thiourea-modified diethylenetriamine.

[0077] A2: Homemade, thiourea-modified triethylenetetramine.

[0078] A3: Homemade, thiourea-modified tetraethylenepentamine.

[0079]

filler

[0080] Calcium carbonate: Calcium carbonate produced by Guangxi Hezhou Kelong Powder Co., Ltd., mesh size is 400 mesh.

[0081]

Active diluent

[0082] B1: NPER-050, produced by Nan Ya Epoxy Resin Co., Ltd., has an epoxy equivalent weight of 120-137 g / eq and a viscosity of 15-20 mPa·s. B2: NPER-048, produced by Nan Ya Epoxy Resin Co., Ltd., has an epoxy equivalent weight of 270-290 g / eq and a viscosity of 5-15 mPa·s.

[0083]

Toughening agent

[0084] C1: Carboxyl-terminated liquid rubber CTBN produced by Jingjiang Tonggao Chemical Co., Ltd., with a rubber content of 99.8%.

[0085] C2: End-epoxy liquid rubber ETBN produced by Jingjiang Tonggao Chemical Co., Ltd., with a rubber content of 99.8%.

[0086] The preparation process is as follows:

[0087] (1) After mixing the epoxy resin and toughening agent, place them in a planetary gravity mixer at a speed of 2000 rpm and stir for 75 seconds; then add the reactive diluent at a speed of 2000 rpm and stir for 75 seconds;

[0088] (2) The mixture of step (1) and the filler were mixed and placed in a planetary gravity mixer at a speed of 2000 rpm for 75 seconds, and repeated twice;

[0089] (3) The mixture of step (2) and the modified amine curing agent were mixed and placed in a planetary gravity mixer at a rotation speed of 1500 rpm and stirred for 60 seconds to finally obtain the room temperature fast curing adhesive composition.

[0090] Table 2

[0091]

[0092]

[0093] Test method used:

[0094] The composition described in the example was prepared according to the above preparation steps. Samples were then prepared for tensile shear testing of 45# steel sheets against steel sheets. The bonding surfaces were polished with 240-grit sandpaper, with the abrasion direction perpendicular to the tensile test direction. Debris and excess grease from the polishing process were removed with a dust-free cloth dipped in a mixture of anhydrous ethanol and acetone. The substrates were allowed to air dry before use. The steel sheets measured 100 mm × 25 mm × 2 mm, with a bonding area of ​​25 mm × 12.5 mm. The samples were cured in an oven at 30°C for 4 hours and then cooled to room temperature.

[0095] According to GBT 7124-2008 test, the tensile shear strength is determined by five passes at a tensile speed of 2 mm / min on a universal tensile testing machine.

[0096] Table 3

[0097] Example Shear strength / MPa Examples and Comparative Examples Shear strength / MPa Example 1 6.7 Example 11 7.62 Example 2 7.15 Example 12 18.33 Example 3 11.97 Example 13 10.57 Example 4 10.27 Example 14 10.1 Example 5 13.28 Example 15 12.58 Example 6 3.56 Example 16 12.55 Example 7 2.27 Example 17 14.83 Example 8 4.46 Comparative Example 1 4.01 Example 9 15.89 Comparative Example 2 8.77 Example 10 14.5 Comparative Example 3 11.8

[0098] As shown in Tables 2 and 3, by comparing the examples with Comparative Example 3, the addition of fillers can reduce costs. When added in small amounts, the cross-linked network after curing of the epoxy resin cannot be well filled. When added in excessive amounts, local stress concentration caused by filler agglomeration reduces the adhesion performance. Examples 5 to 10 show that the addition of a small amount of reactive diluent is beneficial to improving the adhesion performance of the composition. Examples 11 to 16 show that at room temperature, the addition of epoxy-terminated liquid rubber is beneficial to improving the adhesion performance of the composition.

[0099] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for synthesizing a room temperature fast curing agent, characterized in that: Thiourea and polyethylene polyamine are mixed, argon is passed through to protect and exhaust the air, stirring is started and the temperature is uniformly increased, and then the mixture is reacted at a temperature of 110-140° C. for 2.5-4 hours to prepare a modified amine curing agent.

2. The method for synthesizing a room temperature fast curing agent according to claim 1, wherein The polyethylene polyamine is one or more combinations of diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

3. The method for synthesizing a room temperature fast curing agent according to claim 1 or 2, wherein: The molar ratio of the thiourea to the polyethylene polyamine is 1:

1.

4. A room temperature fast curing agent synthesized by the method according to claim 1, characterized in that: The room temperature fast curing agent is a modified amine curing agent.

5. Use of a room temperature fast curing agent synthesized by the method as claimed in claim 1 in epoxy resin adhesive.

6. The use according to claim 5, characterized in that The synthesized curing agent is added to the epoxy resin adhesive system, and the composition, in parts by weight, includes: Epoxy resin 016430-90 parts; 5-20 parts of modified amine curing agent; Filler 0-70 parts; Active diluent 0-10 parts; Toughening agent 0-10 parts.

7. The use according to claim 6, characterized in that The adhesive system comprises: 40-70 parts of epoxy resin 0164; 10-20 parts of modified amine curing agent; 0-40 parts of filler; 1-5 parts of active diluent; and 2-10 parts of toughening agent.

8. The use according to claim 6 or 7, characterized in that The active diluent not only plays the role of a solvent to reduce viscosity but also contains reactive epoxy groups. The active diluent is a compound with two epoxy groups in one molecule, and the viscosity of the active diluent is 1 to 100 mPa·s.

9. The use according to claim 8, characterized in that The active diluent is one or a mixture of allyl glycidyl ether, n-butyl glycidyl ether, phenyl glycidyl ether, methacrylic acid glycidyl ether, diglycidyl ether, polyethylene glycol bisglycidyl ether, polypropylene glycol bisglycidyl ether, and 1,4-butanediol diglycidyl ether.

10. The use according to claim 6 or 7, characterized in that: The toughening agent is a compound with a terminal epoxy group, and the toughening agent is one or a mixture of carboxyl-terminated liquid nitrile rubber, amino-terminated liquid nitrile rubber, hydroxyl-terminated liquid nitrile rubber, and epoxy-terminated liquid nitrile rubber.

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