Anti-skinning filler type polymercaptan epoxy adhesive and preparation method thereof

Abstract

The invention discloses an anti-skinning filler type polymercaptan epoxy adhesive and a preparation method thereof, sheet or layered filler is added into a curing agent and is directionally arranged on the surface layer of the adhesive to form a compact labyrinth type barrier layer, so that permeation of water vapor in air into the adhesive is effectively delayed; the hydrophobic filler is low in surface energy, so that the interaction between the adhesive surface layer and polar substances (such as water and oxygen) in air is reduced, and the curing reaction rate of the surface layer area is slowed down relative to the interior; the filler has good compatibility with a polythiol system, has anti-skinning protection, does not influence the curing effect on epoxy resin components, and has good application effect.

Description

Technical Field

[0001] This invention relates to the field of epoxy adhesive technology, specifically to an anti-skinning filler-type polythiol epoxy adhesive and its preparation method. Background Technology

[0002] Two-component epoxy adhesives (component A: epoxy resin; component B: curing agent) are widely used for structural bonding and sealing in construction, electronics, aerospace, and automotive industries due to their excellent bond strength, chemical resistance, low shrinkage, and good mechanical properties. Polythiol curing agents, with their advantages of rapid room temperature curing, low viscosity, and ability to cure in low-temperature and humid environments, have become the preferred choice for many applications requiring rapid positioning and high-efficiency operation.

[0003] However, in actual construction processes, especially in large-area coatings or operations requiring a long open time (i.e., the time available for application after mixing), traditional polythiol epoxy adhesives have a significant drawback: surface skinning. After the adhesive is mixed and exposed to air for a period of time, its surface will preferentially cure due to interference from moisture and / or oxygen in the air, forming an elastic or brittle skin. This skin severely affects subsequent leveling, bonding, lamination, and other operations, leading to defects at the bonding interface, ultimately affecting bond strength and sealing performance, and resulting in poor appearance. For systems containing fillers, conventional fillers (such as calcium carbonate and quartz powder) have limited effectiveness in mitigating this problem.

[0004] In the existing technology, the methods for delaying epoxy skin formation are mostly focused on adding physical light-blocking agents (such as carbon black) to block ultraviolet rays, or using special amine curing agents. However, these methods often sacrifice curing speed or increase costs, and are not effective in preventing skin formation in polythiol systems.

[0005] Therefore, developing a technology that can maintain the advantages of rapid curing of polythiol epoxy adhesive while effectively preventing surface skinning during construction has significant practical application value. Summary of the Invention

[0006] This invention provides a filler-type polythiol epoxy adhesive that prevents skinning. While maintaining excellent adhesion and rapid curing characteristics, this adhesive can significantly delay the skinning time of the surface exposed to air and extend the open time for construction.

[0007] In view of this, the solution of the present invention is as follows:

[0008] The first aspect of the present invention is to provide an anti-skinning epoxy adhesive curing agent, comprising, by mass percentage: 16-72% polythiol, 0.48-3.6% amine accelerator, 20-80% first filler, and 2-3% first additive; wherein the first filler is a hydrophobic solid, and is in the form of flakes or powder having a layered structure.

[0009] Furthermore, the first filler is selected from one or more of talc powder, mica powder, and talc powder; the mica powder and talc powder are hydrophobically treated.

[0010] Furthermore, the hydrophobic treatment uses a hydrophobic modifier containing at least one functional group that interacts with the target functional group, as well as the remaining hydrophobic functional groups, and the modified hydrophobic functional groups retain their hydrophobic effect.

[0011] Preferably, mica powder is modified for hydrophobicity using siloxanes containing only hydrophobic chains, and talc and bentonite are modified for hydrophobicity using saturated fatty acids, such as stearic acid.

[0012] Furthermore, in the first filler, the thickness of the flakes is in the nanometer to micrometer range, and the particle size D50 of the powder is 5-50 μm; and / or, the bulk density of the first filler is 2.5-3.0 g / cm³. 3 .

[0013] Furthermore, the first adjuvant includes one or more of coupling agents and thixotropic agents.

[0014] Preferably, the coupling agent is a silane coupling agent, more preferably KH-560 coupling agent, and the thixotropic agent is fumed silica.

[0015] Furthermore, the amine accelerator is selected from one or more tertiary amines and imidazole compounds; and / or, the thiol equivalent of the polythiol is 200-240.

[0016] A second aspect of the present invention is to provide an epoxy adhesive comprising component A and component B; wherein component A, by mass percentage, comprises 30-60% epoxy resin, 10-60% second filler, and 2-3% second additive; and component B is the epoxy adhesive curing agent according to any one of claims 1-5.

[0017] Furthermore, the epoxy resin is selected from one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and alicyclic epoxy resin;

[0018] And / or, the second filler is selected from one or more of calcium carbonate, silica powder, and aluminum hydroxide;

[0019] And / or, the second adjuvant is selected from one or more coupling agents and thixotropic agents.

[0020] A third aspect of the invention is to provide the application of the epoxy adhesive described in the second aspect in the field of bonding and sealing.

[0021] Furthermore, in the above applications, during construction, the amounts of component A and component B are controlled so that the mass ratio of epoxy resin to polythiol curing agent is 1:(0.8-1.2).

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The anti-skinning epoxy adhesive curing agent provided by this invention forms a dense "maze" barrier layer by adding sheet-like or layered fillers to the curing agent, which are oriented and arranged on the surface of the adhesive. This effectively delays the penetration of moisture in the air into the interior of the adhesive. The hydrophobic filler has low surface energy, which reduces the interaction between the adhesive surface and polar substances in the air (such as water and oxygen), thus slowing down the curing reaction rate of the surface area compared to the interior. The filler has good compatibility with the polythiol system, providing anti-skinning protection without affecting the curing effect on the epoxy resin components, resulting in good application performance. Detailed Implementation

[0024] The technical solution of the present invention will now be clearly and completely described in conjunction with preferred embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In one embodiment, a filler-type polythiol epoxy adhesive with anti-skinning function is provided, which is a two-component system including component A and component B:

[0026] Component A: By mass percentage, it contains 20%-60% epoxy resin, 30%-70% Class I filler, and 2%-10% additives;

[0027] The epoxy resin is bisphenol A, bisphenol F, alicyclic, or a mixture thereof; the first type of filler is a conventional reinforcing or weight-increasing filler, such as calcium carbonate, silica powder, aluminum hydroxide, etc.; the additives include at least one of coupling agents and thixotropic agents.

[0028] Component B: by mass percentage, it contains 16%-72% polythiol curing agent (generally 0.8-1.2 by mass of resin), 0.48-3.6% accelerator (3%-5% by mass of polythiol), 20%-80% second-class filler, and 2%-3% additives.

[0029] The anti-skinning functional filler is a sheet-like or layered powder material with a hydrophobic surface treatment. Its key characteristic is its ability to physically block the diffusion of moisture from the air into the colloid and slow down the surface curing reaction rate. Preferably, it is one or more of hydrophobically treated mica powder, talc powder, and bentonite. Its dosage is 20%~80% of the total weight of component B, and the bulk density of the anti-skinning functional filler is 2.5-3.0 g / cm³. 3 .

[0030] The polythiol curing agent is a compound containing multiple thiol groups (-SH) in its molecular chain, preferably with a thiol content of [value missing]. The accelerator is an amine accelerator, such as a tertiary amine or an imidazole compound. The additives include coupling agents, thixotropic agents, etc.

[0031] The key innovation of this invention lies in the introduction of a specific anti-skinning filler into the curing agent (component B). Its mechanism of action is as follows:

[0032] 1. Physical barrier function: Sheet or layered fillers are oriented on the adhesive surface, forming a dense "labyrinth" barrier layer that effectively delays the penetration of moisture from the air into the adhesive. The curing of polythiol is highly sensitive to moisture; moisture ingress is a significant factor accelerating surface curing (skinning).

[0033] 2. Reduced surface reactivity: The hydrophobic filler has a low surface energy, which reduces the interaction between the adhesive surface and polar substances in the air (such as water and oxygen), thus slowing down the curing reaction rate of the surface area compared to the interior.

[0034] 3. Synergistic effect: The filler has good compatibility with the polythiol system, does not affect the overall internal curing, and only provides a "delayed" protection effect for the exposed surface.

[0035] In a preferred embodiment, the particle size D50 of the anti-skinning functional filler is between 5 μm and 50 μm, and the thickness is in the nanometer to micrometer range.

[0036] In a preferred embodiment, mica powder is hydrophobically modified using siloxanes containing only hydrophobic chains (such as octyltriethoxysilane and dimethoxysilane), and talc powder and bentonite are modified using saturated fatty acid hydrophobic modification, such as stearic acid.

[0037] In a preferred embodiment, among the above-mentioned additives, the coupling agent is γ-epoxypropoxytrimethoxysilane, preferably KH-560 coupling agent from Wuhan University Organosilicon New Materials. The thixotropic agent is fumed silica, preferably Cabot TS720 hydrophobic fumed silica.

[0038] This invention also provides a method for preparing the above-mentioned adhesive:

[0039] 1) Preparation of component A: Epoxy resin, type I filler, coupling agent, etc. are added to a stirred tank and dispersed uniformly under vacuum at high speed to obtain component A.

[0040] 2) Preparation of component B: Add polythiol curing agent, accelerator, anti-skinning functional filler, thixotropic agent, etc. to another stirred tank, and stir at low speed under vacuum or inert gas protection to disperse evenly, avoiding the introduction of too many air bubbles, to obtain component B.

[0041] 3) When using, mix components A and B in the specified ratio (the mass ratio of epoxy resin to polythiol curing agent is usually between 1:0.8 and 1:1.2) until uniform before application. The strength of the adhesive after application is not affected by the filler in component B.

[0042] Example 1

[0043] 1) Preparation of component A: Mix 50 parts by weight of bisphenol A type epoxy resin (E-51), 48 parts by weight of calcium carbonate, and 2 parts by weight of silane coupling agent KH-560, and disperse evenly under vacuum stirring.

[0044] 2) Preparation of component B: Mix 45 parts by weight of polythiol curing agent (thiol equivalent of about 230), 2 parts by weight of accelerator DMP-30, 50 parts by weight of mica powder treated with octyltriethoxysilane (particle size D50 of about 20 μm), and 3 parts by weight of fumed silica thixotropic agent, and disperse evenly by low-speed stirring under nitrogen protection.

[0045] 3) Mix component A and component B at a weight ratio of 1:1.

[0046] Example 2

[0047] 1) Preparation of component A: Mix 20 parts by weight of bisphenol A type epoxy resin (E-51), 78 parts by weight of calcium carbonate, and 2 parts by weight of silane coupling agent KH-560, and disperse evenly under vacuum stirring.

[0048] 2) Component B is changed to: 20 parts by weight of polythiol curing agent (thiol equivalent of about 235), 2 parts by weight of accelerator DMP-30, 75 parts by weight of stearic acid treated talc powder (particle size D50 of about 15μm), and 3 parts by weight of fumed silica thixotropic agent are mixed and dispersed evenly by low-speed stirring under nitrogen protection.

[0049] 3) Mix component A and component B at a weight ratio of 1:1.

[0050] Example 3

[0051] 1) Preparation of component A: Mix 60 parts by weight of bisphenol A type epoxy resin (E-51), 38 parts by weight of calcium carbonate, and 2 parts by weight of silane coupling agent KH-560, and disperse evenly under vacuum stirring.

[0052] 2) Component B is changed to: 55 parts by weight of polythiol curing agent (thiol equivalent of about 205), 2 parts by weight of accelerator DMP-30, 40 parts by weight of stearic acid treated bentonite (particle size D50 of about 20μm), and 3 parts by weight of fumed silica thixotropic agent are mixed and dispersed evenly by low-speed stirring under nitrogen protection.

[0053] 3) Mix component A and component B at a weight ratio of 1:1.

[0054] Example 4

[0055] 1) Component B is changed to: 45 parts by weight of polythiol curing agent (thiol equivalent of about 230), 2 parts by weight of accelerator DMP-30, 25 parts by weight of stearic acid treated talc (particle size D50 of about 15 μm), 25 parts by weight of stearic acid treated bentonite (particle size D50 of about 20 μm), and 3 parts by weight of fumed silica.

[0056] 2) The rest is the same as in Example 1.

[0057] Example 5

[0058] Component B is modified as follows: 45 parts by weight of polythiol curing agent (thiol equivalent approximately 230), 2 parts by weight of accelerator DMP-30, 25 parts by weight of stearic acid-treated talc powder (particle size D50 approximately 15 μm), 25 parts by weight of mica powder treated with octyltriethoxysilane (particle size D50 approximately 20 μm), and 3 parts by weight of fumed silica are mixed. The rest is the same as in Example 1.

[0059] Example 6

[0060] Component B is modified as follows: 45 parts by weight of polythiol curing agent (thiol equivalent approximately 220), 2 parts by weight of accelerator DMP-30, 25 parts by weight of stearic acid-treated bentonite (particle size D50 approximately 20 μm), 25 parts by weight of mica powder treated with octyltriethoxysilane (particle size D50 approximately 20 μm), and 3 parts by weight of fumed silica are mixed. The rest is the same as in Example 1.

[0061] Example 7

[0062] Component B is modified to be: a mixture of 45 parts by weight of polythiol curing agent (thiol equivalent of about 220), 2 parts by weight of accelerator DMP-30, 17 parts by weight of stearic acid treated talc (particle size D50 of about 15 μm), 17 parts by weight of stearic acid treated bentonite (particle size D50 of about 20 μm), 16 parts by weight of mica powder treated with octyltriethoxysilane (particle size D50 of about 20 μm), and 3 parts by weight of fumed silica.

[0063] The rest is the same as in Example 1.

[0064] Comparative Example 1

[0065] Component B is modified as follows: 45 parts by weight of polythiol curing agent (thiol equivalent approximately 230), 2 parts by weight of accelerator DMP-30, 50 parts by weight of untreated calcium carbonate, and 3 parts by weight of fumed silica are mixed. The rest is the same as in Example 1.

[0066] Comparative Example 2

[0067] Component B is modified as follows: 45 parts by weight of polythiol curing agent (thiol equivalent approximately 230), 2 parts by weight of accelerator DMP-30, 17 parts by weight of untreated talc powder (particle size D50 approximately 15 μm), 17 parts by weight of untreated bentonite (particle size D50 approximately 20 μm), 16 parts by weight of untreated mica powder (particle size D50 approximately 20 μm), and 3 parts by weight of fumed silica are mixed. The rest is the same as in Example 1.

[0068] Performance testing:

[0069] The adhesives prepared in Examples 1, 2, 3, 4, 5, 6, 7 and Comparative Examples 1, 2 were applied as a 2 mm thick layer in an environment of 25°C and 65%RH. The time it took for an irreversible elastic film to begin forming on the surface was observed using the probe method (or finger touch method) and defined as the skinning time. Simultaneously, the tensile shear strength (using a standard steel sheet) after complete curing was tested. The results are shown in Table 1.

[0070] Table 1:

[0071] project Skin formation time (min) Tensile shear strength (MPa) Example 1 800 22.2 Example 2 800 21.5 Example 3 800 21.8 Example 4 900 22.5 Example 5 900 22.3 Example 6 900 22.6 Example 7 1000 23.6 Comparative Example 1 300 22.4 Comparative Example 2 300 23.8

[0072] Test results show that the adhesives prepared in Examples 1-7 have a significantly longer surface skinning time than those in Comparative Examples 1-2 without affecting the final bond strength, demonstrating excellent anti-skinning effect.

[0073] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An anti-skinning epoxy adhesive curing agent, characterized in that, The components, by mass percentage, include: 16-72% polythiol, 0.48-3.6% amine accelerator, 20-80% first filler, and 2-3% first auxiliary agent; the first filler is a hydrophobic powder.

2. The epoxy adhesive curing agent according to claim 1, characterized in that, The first filler is selected from one or more of hydrophobically modified talc powder, mica powder and talc powder.

3. The epoxy adhesive curing agent according to claim 1, characterized in that, The hydrophobic modification uses fatty acids or hydrophobic siloxane modifiers.

4. The epoxy adhesive curing agent according to claim 1, characterized in that, The particle size D50 of the hydrophobic powder is 5-50 μm; And / or, the bulk density of the first filler is 2.5-3.0 g / cm³. 3 .

5. The epoxy adhesive curing agent according to claim 1, characterized in that, The first adjuvant includes one or more of coupling agents and thixotropic agents.

6. The epoxy adhesive curing agent according to claim 1, characterized in that, The amine accelerator is selected from one or more tertiary amines and imidazole compounds; And / or, the thiol equivalent of the polythiol is 200-240.

7. An epoxy adhesive, characterized in that, It includes component A and component B; component A, by mass percentage, comprises 30-60% epoxy resin, 10-60% second filler, and 2-3% second additive; component B is the epoxy adhesive curing agent according to any one of claims 1-6.

8. The epoxy adhesive according to claim 7, characterized in that, The epoxy resin is selected from one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and alicyclic epoxy resin; And / or, the second filler is selected from one or more of calcium carbonate, silica powder, and aluminum hydroxide; And / or, the second adjuvant is selected from one or more coupling agents and thixotropic agents.

9. The application of the epoxy adhesive of claim 7 or 8 in the field of bonding and sealing.

10. The application according to claim 9, characterized in that, During construction, control the amount of component A and component B so that the mass ratio of epoxy resin to polythiol curing agent is 1:(0.8-1.2).