Low-temperature fast-curing epoxy adhesive and preparation method thereof

Abstract

The application discloses a low-temperature rapid curing epoxy adhesive and a preparation method thereof. A component A is composed of an epoxy resin, a diluent and a filler, is uniformly stirred and mixed, and is vacuum degassed to obtain the component A; a component B is composed of a flow agent, a tertiary amine accelerator, a free radical scavenger, a chelating agent and a filler, the thiol, the chelating agent, the filler and the free radical scavenger are uniformly stirred, are slowly stirred and matured for at least 24 hours after passing through a three-roller machine, and then the tertiary amine accelerator is added, and the component B is vacuum degassed to obtain the component B. The thiol and the tertiary amine accelerator are used in combination, the curing speed is the fastest at room temperature, and the gel time of 60s / 25g can be achieved; the metal chelating agent and the free radical scavenger are combined to prevent the thiol from being skinned during storage, and the stable storage time is more than 6 months without skinning. The maturation of the component B enables the chelating agent to fully act on metal ions in the filler, and reduces the influence of the chelating agent on the promoting effect of the tertiary amine accelerator.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of adhesive, and particularly relates to a two-component low-temperature rapid curing epoxy adhesive. BACKGROUND

[0002] Thiol as a curing agent is widely used in the field of room temperature rapid curing epoxy resin adhesive, and has the characteristics of low-temperature rapid curing, low toxicity, high gloss, high gloss, etc. Thiol curing agent is a kind of low-temperature curing agent, but the activity of general thiol is very low when used alone, and it hardly reacts with epoxy resin at room temperature. After being used with amine catalyst, the reaction of thiol and epoxy group is rapid, and even at a low temperature of-20℃, the epoxy resin can also be cured.

[0003] The defects of thiol such as odor and skinning limit its application. The skinning is due to the formation of disulfide by the oxidation of surface thiol molecules. The first step is the oxidation of thiol molecules to form mercapto radicals, and two mercapto radicals combine to form disulfide. More molecules are combined together through disulfide, and finally a skin is formed on the surface. In pure thiol, the formation of disulfide is extremely slow, but in the presence of metal catalyst or amine and other alkaline substances, the skinning of thiol is accelerated. Among metals, iron, copper, cobalt, nickel and other metals can act as catalysts. Although the commercial polythiol has been treated to remove metal ions, the fillers are generally added to the commercially available epoxy products to change the performance of the epoxy resin adhesive and reduce the cost. There are more or less metal compounds in these fillers, especially iron compounds, which are easy to convert between divalent iron and trivalent iron. Trivalent iron is easy to convert thiol into mercapto radical, and oxygen is easy to oxidize divalent iron into trivalent iron. Amine or other alkaline substances in the thiol curing system are used to catalyze the rapid reaction of thiol and epoxy group, which can catalyze the reaction of thiol and epoxy group, and also accelerate the skinning of thiol.

[0004] The patent technology CN 103224769A discloses a method for inhibiting the skinning of thiol, which inhibits the skinning by flushing nitrogen gas and sealing. The method of nitrogen sealing can isolate the surface of thiol solution from air, thereby inhibiting the skinning. However, the method has high requirements for the sealing performance of packaging equipment and containers, otherwise the air in the container cannot be completely discharged, and air will enter the container during storage, although the skinning time is delayed, but the skinning will occur eventually. SUMMARY

[0005] In view of the above defects, the present application provides a low-temperature rapid curing epoxy adhesive, which has high bonding strength, low curing temperature, fast curing speed, good storage stability and is not easy to skin.

[0006] The present application provides a low-temperature rapid curing epoxy adhesive, which is composed of two components A and B.

[0007] The A component comprises, by weight percentage:

[0008] Epoxy resin 30-70%;

[0009] Diluent 1-10%;

[0010] Filler 10-60%;

[0011] The B component comprises, by weight percentage:

[0012]

[0013] The A and B components are not limited in the ratio, preferably 1:1 by volume.

[0014] Preparation method of the A component: the epoxy resin, diluent, and filler are mixed uniformly by a high-speed mixer, then passed through a three-roll mill, and packaged after vacuum bubble removal to obtain the A component.

[0015] Preparation method of the B component: the thiol, chelating agent, filler, and free radical scavenger are first mixed uniformly by a high-speed mixer, then passed through a three-roll mill, and slowly stirred for at least 24 hours, then the tertiary amine accelerator is added, and packaged after vacuum bubble removal to obtain the B component.

[0016] The purpose of the aging of the B component is to allow the chelating agent to fully react with the metal ions in the filler, so that after the addition of the tertiary amine accelerator, the reaction between the chelating agent and the tertiary amine accelerator is reduced, thereby reducing the influence of the chelating agent on the promoting effect of the tertiary amine accelerator. During the aging of the B component, slow stirring is used, and fast stirring speed does not optimize the aging effect. Alternatively, a stirring speed of 10-200 rpm is used.

[0017] The high-speed mixer is a mixer with a stirring speed adjustable in the range of 0-1800 rpm. The raw materials are mixed uniformly by using the high-speed mixer, and the stirring speed is adjusted according to the actual requirements until the mixture is uniform.

[0018] The epoxy resin is an epoxy compound having at least two epoxy groups per molecule, preferably an epoxy compound having two epoxy groups, which can be selected from one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, glycidyl amine epoxy resin, glycidyl ester epoxy resin, alicyclic epoxy resin, and phenolic epoxy resin.

[0019] The epoxy resin is more preferably a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, or a mixture of the two. The bisphenol A type epoxy resin can be selected from NPEL-128E of Nan Ya, and the bisphenol F type epoxy resin can be selected from NPEF-170 of Nan Ya, or EPALLOY 8220 and EPALLOY 8230 of CVC.

[0020] The epoxy resin is added in a proportion of 30 to 70% by weight based on the total weight of the A component.

[0021] The diluent is an epoxy diluent including any one of butyl glycidyl ether, benzyl glycidyl ether, octyl glycidyl ether, dodecyl glycidyl ether, tridecyl glycidyl ether, tetradecyl glycidyl ether, butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycidyl neodecanoate, or a combination of at least two thereof.

[0022] The diluent is added in a proportion of 1 to 10% by weight based on the total weight of the A component.

[0023] The filler is one or more of alumina powder, magnesium oxide, calcium oxide, calcium carbonate, talc powder, silica powder, mica powder, aluminum hydroxide, magnesium hydroxide, barium sulfate, decabromodiphenyl ethane, melamine cyanurate (MCA). The filler preferably contains less than 1% of oxides or salts of iron, copper, cobalt, and nickel, and more preferably contains less than 0.5% of oxides or salts of iron. If the content of the oxides or salts of iron, copper, cobalt, and nickel is too high, the amount of the chelating agent to be added is also high, and the high amount of the chelating agent reacts with the tertiary amine accelerator, thereby weakening the accelerating effect of the tertiary amine accelerator and slowing the curing speed.

[0024] The filler is added in a proportion of 10 to 60% by weight based on the total weight of the A component or the B component.

[0025] The filler types and proportions of the A component and the B component can be the same or different.

[0026] The mercaptan is a mercaptan compound having two or more mercaptan groups in the molecule.

[0027] The mercaptan can be selected from Capcure 3-800, Capcure 40sce HV, Capcure WR-6, Capcure 3830-81, Capcure LOF of Huntsman, trimethylolpropane tris(3-mercaptopropionate) (TMPMP), pentaerythritol tetra(3-mercaptopropionate) (PETMP), ethylene glycol di(3-mercaptopropionate) (GDMP), 1,4-butanediol di(3-mercaptopropionate) (BDMP), 2,3-bis(2-mercaptoethylthio)propane-1-thiol of SC Organic Chemicals.

[0028] The mercaptan is added in a proportion of 20 to 60% by weight based on the total weight of the B component.

[0029] The tertiary amine accelerator can be selected from one or more of triethanolamine, N,N-dimethylpiperazine, triethylenediamine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), dimethylaminomethylphenol (DMP-10).

[0030] The addition ratio of the tertiary amine accelerator is 1-10% based on the weight of all B components.

[0031] If the amount of the tertiary amine accelerator is too small, the promotion of the reaction of the mercaptan with the epoxy resin is not enough, and the reaction speed is slow. If the amount of the tertiary amine accelerator is greater than a certain ratio, the improvement of the reaction speed of the mercaptan with the epoxy resin is not obvious, and more mercaptan salt anions are generated, which are further oxidized to generate more mercapto radicals, thereby accelerating the formation of the skin.

[0032] The radical scavenger is preferably a nitroxyl radical compound. The nitroxyl radical compound can comprise at least one component selected from 2,2,6,6-tetramethyl-1-piperidinyloxy radical (TEMPO), 4-acetamide-2,2,6,6-tetraethylpiperidine-1-oxyl radical, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl radical, 4-carboxy-2,2,6,6-tetramethylpiperidine-1-oxyl radical, 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl radical, 4-methylpropionyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl radical, [[N,N'-[adamantane-2-ylidenebis(1,4-phenylene)]bis(tert-butylamine)]-N,N'-diylbisoxyl] radical.

[0033] The nitroxyl radical compound has strong radical scavenging ability, and can not only capture oxygen radicals, but also react with mercapto radicals, which can reduce the oxidation of mercaptans and react with the mercapto radicals generated after the oxidation of mercaptans to avoid the formation of disulfides.

[0034] The addition ratio of the nitroxyl radical compound is 0.01-0.5%, more preferably 0.03-0.1%, based on the weight of all B components. If the addition ratio is too small, the radical scavenging ability is insufficient, and the improvement of the mercaptan skin is not obvious. If the addition ratio is too high, the nitroxyl radical compound itself has a certain oxidizing property, which can accelerate the formation of disulfides, thereby forming the skin faster.

[0035] The chelating agent can be selected from aminocarboxylic acids, organic polyphosphoric acids, thiourea derivatives, etc., among which typical organic polyphosphoric acids include: ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, H-501, hydroxyethylidene-1,1-diphosphonic acid; typical thiourea derivatives include methylthiourea pyridine, propylthiourea pyridine, malonylthiourea, N-ethylthiourea, N,N-diethylthiourea, N-butylthiourea, N-phenylthiourea or N-methyl-N-phenylthiourea; typical aminocarboxylic acids include ethylenediaminetetraacetic acid (EDTA), aminotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA) and their salts, etc.

[0036] The chelating agent is added at a rate of 0.05% to 0.5%.

[0037] The chelating agent functions by forming stable chelates with metal ions in the system, thereby eliminating their redox capabilities and improving the stability of the thiol system. This significantly delays the formation of a skin. If too little chelating agent is added, it cannot fully interact with the metal ions in the system, thus failing to delay the formation of a skin. If too much chelating agent is added, it interacts with the tertiary amine accelerator, weakening the accelerating effect of the tertiary amine accelerator and slowing down the curing speed.

[0038] Compared with the prior art, the present invention has at least the following beneficial effects.

[0039] The combination of thiol and tertiary amine accelerators can achieve rapid curing at low temperatures, with the fastest curing speed at room temperature (25℃) reaching a gel time of 60s / 25g.

[0040] Metal chelating agents form stable chelates with metal ions, preventing them from reacting with thiols and causing oxidation. Free radical scavengers eliminate free radicals generated during thiol oxidation, preventing the formation of disulfides and thus preventing thiols from forming a skin during storage. The combined action of metal chelating agents and free radical scavengers effectively prevents disulfide formation without affecting the formation of thiolate anions (thiolate anions are essential intermediates for thiol curing; slowing down the formation of thiolate anions will reduce the curing rate of thiols). Therefore, while preventing thiols from forming a skin, the curing rate of thiols is not affected.

[0041] In the preparation of component B, the thiol, chelating agent, filler, and free radical scavenger are first mixed evenly, passed through a three-roll mill, and then slowly stirred and matured for at least 24 hours. Then, the tertiary amine accelerator is added. The purpose of maturing component B is to allow the chelating agent to fully interact with the metal ions in the filler. This reduces the interaction between the chelating agent and the tertiary amine accelerator after the addition of the tertiary amine accelerator, thereby reducing the influence of the chelating agent on the promoting effect of the tertiary amine accelerator.

[0042] Epoxy adhesives have good storage stability. They can be stored stably for more than 6 months without forming a skin, even when packaged in ordinary plastic buckets.

[0043] The epoxy adhesive exhibits excellent adhesion after curing. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] Examples and Comparative Examples

[0046] Preparation methods of low-temperature rapid-curing epoxy adhesives in each embodiment:

[0047] Prepare the raw materials according to the amounts shown in Table 1, and then prepare components A and B respectively using the following preparation methods:

[0048] Preparation method of component A: Epoxy resin, diluent and filler are mixed evenly with a high-speed mixer, then passed through a three-roll mill, vacuum defoamed and packaged to obtain component A.

[0049] Preparation method of component B: First, mix the thiol, chelating agent, filler and free radical scavenger evenly with a high-speed mixer, pass through a three-roll mill and then slowly stir (stirring speed 50 rpm) for at least 24 hours. Then add the tertiary amine accelerator, vacuum degas and package to obtain component B.

[0050] Comparative method for preparing epoxy adhesives:

[0051] Except for omitting some ingredients or changing the amount of some ingredients, the other conditions are the same as in the examples. The raw material composition of the comparative examples is shown in Table 1.

[0052] Table 1. Raw material types and amounts (mass, parts) for the examples and comparative examples

[0053]

[0054]

[0055] After preparing components A and B for each embodiment and comparative example, the A and B components were mixed in a volume ratio of 1:1 to form an epoxy adhesive. The gel time, shear strength, and skinning time were tested using the following method, and the results are shown in Table 2.

[0056] Gel time measurement method: Take an appropriate amount of 25g of components A and B respectively, mix them evenly according to the ratio, and measure the gel time according to GBT7193.6.

[0057] Shear strength measurement method: Take appropriate amounts of A and B component samples respectively, mix them evenly according to the ratio, prepare Al-Al shear sheets according to GB / T7124, cure at room temperature for 12 hours and then measure the shear strength using a tensile testing machine.

[0058] Skinning time test method: Take component B and put it into the paint bucket, filling it to 90% of the rated volume. Then tighten the lid and periodically open the lid to visually observe whether a skin has formed.

[0059] Table 2. Test results of the examples and comparative examples.

[0060] Test item Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Gel time 3 min 60s 4 min 6 min 15 min 3 min 60s 3 min Shear strength 29 MPa 27 MPa 30 MPa 33 MPa 28 MPa 27 MPa 18 MPa 29 MPa Skinning time 8 months 6 months 7 months 10 months 9 months 45 days 1 month 10 days

[0061] As can be seen from Table 2:

[0062] 1. Examples 1-4 are low-temperature rapid curing epoxy adhesives with gel time within a few minutes, and as fast as 60 seconds. They have high shear strength, good storage stability, and a skinning time of more than 6 months under normal storage conditions.

[0063] 2. Comparative Example 1 increased the amount of chelating agent added based on Example 1, resulting in a longer gelation time.

[0064] 3. Comparative Example 2 increased the amount of free radical scavenger added based on Example 1, resulting in poor storage stability and rapid skin formation.

[0065] 4. Comparative Example 3 increased the amount of tertiary amine accelerator compared to Example 1. As a result, the gelation time became shorter, the storage stability deteriorated, and the gel quickly formed a skin.

[0066] 5. In Comparative Example 4, the filler used had a high Fe2O3 content, resulting in poor storage stability and rapid crusting.

[0067] 6. Comparative Example 5 and Example 1 have the same raw material ratio, except that the order of adding raw materials of component B is different. The tertiary amine promoter is added after the raw material has not been cured. Skin formation occurs after 2 months, and the skin formation time is shortened.

[0068] Although the invention has been described herein with reference to illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of the principles disclosed herein. More specifically, various variations and modifications can be made to the components and / or layout of the subject matter combination within the scope of this disclosure. Besides variations and modifications to the components and / or layout, other uses will be apparent to those skilled in the art.

Claims

1. A low-temperature, fast-curing epoxy adhesive, comprising component A and component B, characterized in that, Component A is made of epoxy resin, diluent, and filler; Component B comprises, by weight percentage: Thiols 20-60%; Tertiary amine accelerator 1~10%; Free radical scavenger 0.01~0.5%; Chelating agent 0.05~0.5%; Filler content: 10-60%; The chelating agent is selected from any one of ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, H-501, hydroxyethylidene-1,1-diphosphonic acid, methylthiourea pyridine, propylthiourea pyridine, malonylthiourea, N-ethylthiourea, N,N-diethylthiourea, N-butylthiourea, N-phenylthiourea or N-methyl-N-phenylthiourea, ethylenediaminetetraacetic acid (EDTA), aminotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), and their salts; The content of any one of the oxides or salts of iron, copper, cobalt, and nickel in the filler is less than 1%; the filler is one or more of alumina powder, magnesium oxide, calcium oxide, calcium carbonate, talc powder, silica powder, mica powder, aluminum hydroxide, magnesium hydroxide, barium sulfate, decabromodiphenyl ethane, and melamine cyanurate.

2. The low-temperature rapid-curing epoxy adhesive according to claim 1, characterized in that, Component A comprises, by weight percentage: Epoxy resin 30~70%; Diluent 1~10%; Filler content: 10-60%.

3. The low-temperature rapid-curing epoxy adhesive according to claim 1 or 2, characterized in that, The free radical scavenger is selected from one or more of the following: 2,2,6,6-tetramethyl-1-piperidine-oxy radical, 4-acetamide-2,2,6,6-tetraethylpiperidine-1-oxy radical, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxy radical, 4-carboxyl-2,2,6,6-tetramethylpiperidine-1-oxy radical, 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxy radical, 4-methylacryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxy radical, and [[N,N'-[adamantane-2-ethylenedioxybis(1,4-phenylene)]bis(tert-butylamine)]-N,N'-dimethyldioxy] radical.

4. The low-temperature rapid-curing epoxy adhesive according to claim 1 or 2, characterized in that, The thiol is selected from one or more of Capcure 3-800, Capcure 40 sce HV, Capcure WR-6, Capcure 3830-81, Capcure LOF, trimethylolpropane tris(3-mercaptopropionic acid), pentaerythritol tetra(3-mercaptopropionic acid), ethylene glycol di(3-mercaptopropionic acid), 1,4-butanediol di(3-mercaptopropionic acid), and 2,3-bis(2-mercaptoethylthio)propane-1-thiol; The tertiary amine accelerator is selected from one or more of triethanolamine, N,N-dimethylpiperazine, triethylenediamine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and dimethylaminomethylphenol.

5. The low-temperature rapid-curing epoxy adhesive according to claim 1 or 2, characterized in that, The epoxy resin is selected from one or more of the following: bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, glycidylamine epoxy resin, glycidyl ester epoxy resin, alicyclic epoxy resin, and phenolic epoxy resin.

6. The low-temperature rapid-curing epoxy adhesive according to claim 1 or 2, characterized in that, The diluent is selected from any one or a combination of at least two of the following: butyl glycidyl ether, benzyl glycidyl ether, octyl glycidyl ether, dodecyl glycidyl ether, tridecyl glycidyl ether, tetradecyl glycidyl ether, butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and neodecanoic acid glycidyl ester.

7. The low-temperature rapid-curing epoxy adhesive according to claim 1 or 2, characterized in that, The components A and B are used in a 1:1 volume ratio.

8. The method for preparing the low-temperature rapid-curing epoxy adhesive according to claim 1 or 2, characterized in that, Includes the following steps: (1) Mix epoxy resin, diluent and filler evenly, and then vacuum degas to prepare component A; (2) First, mix the thiol, chelating agent, filler and free radical scavenger evenly, pass through a three-roll mill and stir and mature for at least 24 hours, then add the tertiary amine accelerator and vacuum degas to obtain component B.

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