Epoxy adhesive and use and preparation method thereof

Abstract

One-component adhesive compositions suitable for sealing threaded articles, methods of use thereof, and products thereof are provided. The one-component adhesive composition includes a plurality of microcapsules and a dispersed matrix, where each of the plurality of microcapsules includes a core and a shell at least partially surrounding the core, where the core comprises a polyamine, the shell comprises a crosslinked polyurea, and the dispersed matrix comprises an epoxy resin.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 602,671, filed on November 27, 2023, the entire contents of which are hereby incorporated by reference herein. Technical Field

[0003] The present disclosure relates to a one-component adhesive composition suitable for fastening and sealing threaded articles, methods of using the same, and products thereof. Background Art

[0004] Threaded components, as important removable elements used to seal and protect substrates, play a key role in the construction, installation and maintenance of machinery. The main factors leading to the failure of these components are tension relaxation and self-loosening. Current solutions, such as adhesive bonding and mechanical fastening (including threadlockers, thread sealants, screws and nuts, studs and nuts, and self-tapping screws), all have certain limitations. These challenges are mainly related to labor intensity, the necessity of on-site mixing, and material waste.

[0005] The widespread use of liquid anaerobic adhesives in mechanical assembly is increasingly incompatible with the requirements of modern automated production lines. These adhesives need to be applied immediately before use, are inefficient, prone to dripping, and often cause workpiece contamination and material waste. The introduction of pre-applied anaerobic adhesives developed in the 1980s provided a solution to these problems. These adhesives allow for early application to fasteners, allowing for immediate use after application or centralized storage. This advancement eliminated the disadvantages associated with traditional liquid adhesives, such as dripping and inefficient field operations.

[0006] Currently, two-component water-based acrylate adhesives dominate the market. These adhesives consist of acrylate monomers (component A) and microencapsulated initiators (component B). When mixed and applied to the threads, these components dry to form a reactive adhesive film. During assembly, the microcapsules rupture and release the initiator, which triggers the polymerization of the acrylate monomers, thus filling the gaps and preventing loosening. Although 204 and Two-component pre-coated anaerobic adhesives such as 2041 are widely used, but they are not without limitations. Due to equipment limitations, manual mixing is usually required, which may result in inconsistent mixtures, affect fastening quality, and pose risks to the assembled product. In addition, these adhesives have a limited room temperature shelf life after mixing (usually within 6 hours), which may cause waste and inconvenience. In addition, traditional water-based threadlocking adhesives contain hydrophilic materials that tend to absorb moisture after application, which may affect the cure strength and effectiveness.

[0007] Epoxy resin is a class of adhesives with superior performance, whose advantages include adjustable mechanical properties, excellent thermal stability and chemical resistance, high electrical insulation, good adhesion, etc. It is widely used in adhesives, coatings, sealants, molding compounds and other fields, involving electronics, industry, aviation and other industries. Compared with amine curing agents that are susceptible to chemical attack and pose greater environmental risks, epoxy resins are easier to microencapsulate.

[0008] With the advancement of adhesive technology, solvent-based one-component adhesives have been developed in which epoxy microcapsules are dispersed in amine curing agents (CN104893635A and CN111518500A), allowing long-term pre-coating. However, these technologies do not completely address the challenges posed by amine curing agents. Patents such as JP 5543879B2 introduce a one-component epoxy adhesive using a microencapsulated curing agent as a latent curing agent. However, the core curing agent is based on imidazole chemistry and the core is in solid form, which may hinder the uniform distribution of the core when released. In addition, important market segments of curing agents including aliphatic, aromatic and polyether amines have not yet seen microcapsule-based one-component adhesive formulations.

[0009] Another key issue with traditional threadlocking adhesives is that they rely on volatile solvents for film formation, which raises environmental concerns. The industry has yet to develop a solvent-free, one-component adhesive that can serve as an environmentally friendly threadlocking solution.

[0010] Epoxy / amine systems are known for their adaptability, mechanical strength, and resistance to harsh environmental conditions such as thermal shock and chemical attack. Epoxy resins are relatively stable and can be easily microencapsulated. However, amine curing agents are not only more susceptible to chemical degradation when exposed to the environment, but also cause more environmental hazards, which brings challenges to the use of amine curing agents in epoxy / amine systems.

[0011] Therefore, there is a need for improved one-component adhesives that address or overcome at least some of the above-mentioned shortcomings. This article describes an innovative method for fastening threaded assemblies using a one-component epoxy adhesive incorporating amine microcapsules. This unique adhesive can be pre-applied to the threads, initiating the curing and bonding process only when the threads are assembled. Mechanical pressure is applied to trigger the rupture of the amine microcapsules, thereby triggering the polymerization process. This method utilizes the robustness of epoxy resins in a more efficient and user-friendly manner. This design is intended to circumvent the drawbacks of existing methods, thereby providing a better alternative that enhances the practicality and effectiveness of threaded assembly maintenance and repair. Summary of the invention

[0012] Provided herein are one-component adhesive compositions that incorporate microencapsulated amines dispersed in an epoxy matrix as a threadlocking adhesive.

[0013] In a first aspect, the present invention provides a one-component adhesive composition comprising a plurality of microcapsules and a dispersion matrix, wherein each of the plurality of microcapsules comprises a core and a shell at least partially surrounding the core, wherein the core comprises a polyamine, the shell comprises a cross-linked polyurea, and the dispersion matrix comprises an epoxy resin.

[0014] In certain embodiments, the plurality of microcapsules has an average diameter of 10-300 μm.

[0015] In certain embodiments, the polyamine comprises a polyalkylamine, a polyetheramine, a polyarylamine, or a mixture thereof.

[0016] In certain embodiments, the polyamine comprises triethylenetetramine (TETA), tetraethylenepentamine (TEPA), polyoxypropylenetriamine, or a mixture thereof, the polyoxypropylenetriamine being represented by the formula:

[0017]

[0018] Wherein m+n+p is 5 to 6.

[0019] In certain embodiments, the crosslinked polyurea includes a polyamine crosslinked with a diisocyanate, a polyisocyanate, or a mixture thereof.

[0020] In certain embodiments, the crosslinked polyurea includes a polyamine crosslinked with 4,4'-dicyclohexylmethane diisocyanate.

[0021] In certain embodiments, the polyamine includes TETA, TEPA, or TEPA and polyoxypropylene triamine.

[0022] In certain embodiments, the polyamine includes TEPA and polyoxypropylene triamine, wherein the molar ratio of TEPA to the amine in the polyoxypropylene triamine is 1:3 to 3:1, respectively.

[0023] In certain embodiments, the epoxy resin includes bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, novolac epoxy resin, alicyclic epoxy resin, glycidyl ester epoxy resin, glycidyl ether resin, glycidyl amine epoxy resin, halogenated epoxy resin or mixtures thereof.

[0024] In certain embodiments, the epoxy resin includes bisphenol A type epoxy resin and bisphenol F type epoxy resin.

[0025] In certain embodiments, the polyamine comprises triethylenetetramine (TETA), tetraethylenepentamine (TEPA), polyoxypropylenetriamine, or a mixture thereof, the polyoxypropylenetriamine being represented by the formula:

[0026]

[0027] Where m+n+p is 5 to 6;

[0028] The crosslinked polyurea includes a polyamine crosslinked with 4,4′-dicyclohexylmethane diisocyanate;

[0029] Epoxy resins include bisphenol A type epoxy resins and bisphenol F type epoxy resins.

[0030] In certain embodiments, the plurality of microcapsules and the dispersion matrix are present in a mass ratio of 3:17 to 1:3, respectively.

[0031] In certain embodiments, the dispersed matrix further comprises a partially cured epoxy resin formed by the reaction of an epoxy resin and a polyamine.

[0032] In certain embodiments, 10-30 mol % of the epoxy resin is reacted with the polyamine in the dispersed matrix.

[0033] In certain embodiments, the epoxy resin further includes a polyamine curing agent, a polythiol curing agent, or a mixture thereof.

[0034] In certain embodiments, the plurality of microcapsules and the dispersion matrix are present in a mass ratio of about 1:4, respectively; and the dispersion matrix further comprises a partially cured epoxy resin formed by the reaction of an epoxy resin and a polyamine, wherein in the dispersion matrix, 10-30 mol% of the epoxy resin reacts with the polyamine.

[0035] In certain embodiments, the polyamine includes TEPA and polyoxypropylene triamine, wherein the molar ratio of TEPA to the amine in the polyoxypropylene triamine is about 3: about 1, respectively.

[0036] In a second aspect, provided herein is a method comprising depositing the one-component adhesive composition described herein onto a surface of a substrate and curing the one-component adhesive composition to form a cured one-component adhesive composition.

[0037] In certain embodiments, the substrate includes a threaded component.

[0038] In certain embodiments, curing comprises subjecting the one-part adhesive composition to 25-100° C. for 1-24 hours.

[0039] In certain embodiments, curing comprises subjecting the one-part adhesive composition to 35-55°C for 1-24 hours, 20-25°C for 1-24 hours, 40-100°C for 1-24 hours.

[0040] In a third aspect, provided herein is a cured one-component adhesive composition prepared according to the method described herein.

[0041] Based on this, this application introduces a breakthrough solvent-free, one-component adhesive that incorporates microencapsulated amines into epoxy resins, specifically designed as a threadlocking solution. In addition, a method has been developed to partially cure the epoxy resin without the use of volatile solvents, thereby achieving an optimal balance between surface dryness and adhesive integrity. This innovative solvent-free adhesive can be pre-applied to fastening components such as screws, thereby extending storage and facilitating application without the need to worry about VOC emissions. The characteristics of this adhesive include Figure 1 As shown, Figure 1 Shown is a one-component epoxy adhesive viewed under an optical microscope.

[0042] The application process is streamlined and efficient: When the screw is tightened, the microcapsules rupture, releasing the encapsulated amine, which initiates the polymerization reaction. Figure 2 Illustrating this critical process, the figure provides a cross-sectional view of a hexagon head screw treated with the microencapsulated adhesive of the present application. The action of tightening the screw accelerates the curing process, avoiding the need for a separate mixing procedure and improving the overall productivity of the assembly operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above-described aspects of the present invention and many of the attendant advantages will be more readily understood and appreciated by reference to the following detailed description, taken in conjunction with the accompanying drawings.

[0044] Figure 1 Depicted are optical microscopy images under white light showing relatively uniform cured areas of a one-component epoxy adhesive according to certain embodiments described herein.

[0045] Figure 2 Depicted is a schematic cross-sectional view of a hex head screw with a one-component microcapsule-based epoxy adhesive according to certain embodiments described herein.

[0046] Figure 3A-3E The dependence of the glass transition temperature on the concentration of tetraethylenepentamine (TEPA), triethylenetetramine (TETA), a mixture of TEPA and T403 and a mixture containing TEPA and T403 with a molar ratio of -NH of 75% and 25%, respectively (75TEPA25T403), T403 and a mixture (50TEPA50T403) in which the molar ratio of -NH contributed by TEPA and T403 is 50% and 50%, respectively, and a mixture comprising TEPA and T403 and a mixture in which the molar ratios of -NH contributed by TEPA and T403 are 25% and 75%, respectively (25TEPA75T403).

[0047] Figure 4 Depicted is a bar graph showing break-loose torque results for screws treated with different types of neat amine / epoxy mixtures (composed of 0% microcapsules and 100% liquid amine curing agent) according to certain embodiments described herein.

[0048] Figure 5A shows an overview of PU-75TEPA25T403 microcapsules according to certain embodiments described herein; Figure 5B A cross-sectional view of the shell is shown; Figure 5C showing the inner surface of the microcapsule; and Figure 5D The outer surface of the microcapsule is shown.

[0049] Figure 6 Depicted is a TGA curve of intact PU-75TEPA25T403 core-shell microcapsules including a core comprising 75TEPA25T403 and a shell comprising 75TEPA25T403 cross-linked with 4,4'-dicyclohexylmethane diisocyanate according to certain embodiments described herein.

[0050] Figure 7 The depicted table shows the evolution of 75TEPA25T403 amine microcapsule-epoxy (epoxy resin sold under the trade name Epolam 5015 resin) one-component adhesive (composed of 80% microcapsules and 20% curing agent) according to certain embodiments described herein at different standing times at 40°C according to ISO 9117-5: Drying test.

[0051] Figure 8 The depicted photograph shows a surface drying test of a screw glued with 75TEPA25T403 amine microcapsule-epoxy (epoxy resin sold under the trade name Epolam 5015 resin) one-component adhesive (composed of 80% microcapsules and 20% curing agent) according to certain embodiments described herein at 40°C for 15 hours.

[0052] Fig. 9 The bar graph depicted shows the breakloose torque results for M10 screws treated with 75TEPA25T403 amine microcapsule-epoxy (epoxy resin sold under the trade name Epolam 5015 resin) one-component adhesive (composed of 80% microcapsules and 20% curing agent) of certain embodiments described herein at different microcapsule sizes and curing temperatures.

[0053] Fig.10The bar graph depicted shows the breakaway torque results for screws treated with 75TEPA25T403 amine microcapsule-epoxy (epoxy resin sold under the trade name Epolam 5015 resin) one-component adhesive (consisting of 80% microcapsules and 20% curing agent) of certain embodiments described herein at different curing durations and curing temperatures. DETAILED DESCRIPTION

[0054] definition

[0055] The following terms are used to describe the present invention. Unless otherwise specifically defined herein, the terms used to describe the present invention shall have the common meanings understood by those of ordinary skill in the art.

[0056] Throughout the application, when compositions are described as having, including, or comprising specific components, or when methods are described as having, including, or comprising specific process steps, it should be considered that the compositions of the present teachings may also consist essentially of or consist of the components, and the methods of the present teachings may also consist essentially of or consist of the process steps.

[0057] In the present application, when an element or component is described as being included in and / or selected from a list of elements or components, it should be understood that the element or component can be any one of the elements or components, or the element or component can be selected from a group consisting of two or more of the elements or components. In addition, it should be understood that the elements and / or features of the compositions or methods described herein can be combined in a variety of ways without departing from the subject and scope of the teachings of the present application, whether or not expressly or implicitly stated herein.

[0058] It should be understood that, as long as the teaching of the present application is feasible, the order of steps or the order in which certain actions are performed is not important. In addition, two or more steps or actions can be performed simultaneously.

[0059] Unless otherwise expressly stated, the singular as used herein includes the plural (and vice versa). In addition, if the term "about" is used before a quantitative value, the present teachings also include the specific quantitative value itself unless otherwise expressly stated. Unless otherwise stated or inferred, the term "about" as used herein refers to a difference of ±10%, ±7%, ±5%, ±3%, ±1% or ±0% from the nominal value.

[0060] The present disclosure provides a one-component adhesive composition comprising a plurality of microcapsules and a dispersion matrix, wherein each of the plurality of microcapsules comprises a core and a shell at least partially surrounding the core, wherein the core comprises a polyamine, the shell comprises a cross-linked polyurea, and the dispersion matrix comprises an epoxy resin.

[0061] In certain embodiments, the one-part adhesive composition does not include a solvent.

[0062] The polyamines include polyalkylamines, polycycloalkylamines, polyetheramines, polyarylamines or mixtures thereof. Each polyamine may contain at least two, at least three, at least four or more amines reactive to epoxy groups (eg, primary and / or secondary amine groups).

[0063] Exemplary polyamines include, but are not limited to, 1,2-ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,2-butylenediamine, 1,3-butylenediamine, 1,4-butylenediamine, 2,3-butylenediamine, 2-methyl-1,3-propylenediamine, 2,2-dimethyl-1,3-propylenediamine, 1,3-pentanediamine (DAMP), 1,5-pentanediamine, 1,5-diamino-2-methylpentane (MPMD), 1,6-hexanediamine, 2,5-dimethyl-1,6-hexanediamine, 2,2,4- or 2,4,4-trimethylhexanediamine ( TMD), 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane (isophoronediamine or IPDA), 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 2- or 4-methyl-1,3-diaminocyclohexane or mixtures thereof, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 2,5 or 2,6-bis(aminomethyl)bicyclo[2.2 .1] heptane (NBDA), 1,4-diamino-2,2,6-trimethylcyclohexane (TMCDA), 1,8-menthandiamine, 1,3-bis(aminomethyl)benzene (MXDA), 1,4-bis(aminomethyl)benzene, bis(2-aminoethyl)ether, 3,6-dioxaoctane-1,8-diamine, 4,7-dioxadecane-1,10-diamine, 4,7-dioxadecane-2,9-diamine, 3-(2-aminoethyl)aminopropylamine, bis(hexamethylene) ) triamine (BHMT), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), dipropylenetriamine (DPTA), N-(2-aminoethyl)-1,3-propylenediamine (N3-amine), N,N'-bis(3-aminopropyl)ethylenediamine, N,N'-bis(3-aminopropyl)-1,4-diaminobutane, (3-aminopropyl)-2-methyl-1,5-pentanediamine or N-(3-aminopentyl)-1,3-pentanediamine, D-230, D-400, D-2000, T-403, T-3000, T-5000 or a mixture thereof. In certain embodiments, the polyamines include TETA, TEPA, T-403 or a mixture thereof.

[0064] T-403, T-3000 and T-5000 can be expressed as follows:

[0065]

[0066] Among them, m+n+p are 5.3, 50.3 and 84.8 respectively.

[0067] D-230, D-400 and D-2000 can be expressed as follows:

[0068]

[0069] where p is 2.5, 5.6 and 33.1 respectively.

[0070] In certain embodiments, the polyalkylamine comprises TETA or TEPA and T-403, of which TETA or TEPA and The molar ratios of amines in T-403 are 1:3 to 3:1, 1:3 to 1:1, and 1:1 to 3:1, respectively. In certain embodiments, the polyalkylamines include TEPA and T-403, of which TEPA and The molar ratio of amines in T-403 is about 3: about 1 respectively.

[0071] The cross-linked polyurea may include a polyamine cross-linked with a polyisocyanate. Polyisocyanates suitable for use in the compositions described herein include, but are not limited to, diisocyanates, polyisocyanate biuret of isocyanates and polyisocyanates, isocyanurates of isocyanates and polyisocyanates, and combinations thereof. The polyisocyanate may include a polyisocyanate selected from aromatic polyisocyanates, aliphatic polyisocyanates, and combinations thereof. Exemplary polyisocyanates include, but are not limited to, 2,4-toluene diisocyanate (TDI), 2,6-toluene diisocyanate, trimethylhexamethylene diisocyanate (TMDI), 4,4′-diphenylmethane diisocyanate (MDI), 4,4′-dicyclohexylmethane diisocyanate (HDI), and 4,4′-dicyclohexylmethane diisocyanate (HDI). 12 MDI), 3,3′-dimethyl-4,4′-biphenyl diisocyanate (TODI), dodecane diisocyanate (C 12DI), tetramethyl meta-xylylene diisocyanate (TMXDI), 1,4-phenylene diisocyanate, trans-cyclohexane-1,4-diisocyanate, 1,5-naphthalene diisocyanate (NDI), 1,6-hexamethylene diisocyanate (HDI), 4,6-xylylene diisocyanate, isophorone diisocyanate (IPDI) and combinations thereof. In certain embodiments, the crosslinked polyurea includes HDI and isophorone diisocyanate. 12 MDI cross-linked TETA, TEPA or containing TETA or TEPA and A mixture of T-403.

[0072] Relative to the total weight of the polyamine and the cross-linked polyurea, each microcapsule in the plurality of microcapsules may contain 70-95wt%, 75-95wt%, 80-95wt%, 85-95wt%, 90-95wt%, 70-90wt%, 70-85wt%, 70-80wt%, 70-75wt% or 75-85wt% of the polyamine. In certain embodiments, each microcapsule in the plurality of microcapsules contains about 80wt% of the polyamine relative to the total weight of the polyamine and the cross-linked polyurea.

[0073] The plurality of microcapsules may have an average diameter of 10-500 μm, 50-500 μm, 100-500 μm, 150-500 μm, 200-500 μm, 250-500 μm, 300-500 μm, 350-500 μm, 400-500 μm, 450-500 μm, 50-450 μm, 50-400 μm, 50-350 μm, 50-300 μm, 50-250 μm, 50-200 μm, 50-150 μm, 50-100 μm, 50-300 μm, 100-300 μm, 150-300 μm, 200-300 μm, 250-300 μm, 50-150 μm, or 75-125 μm. In certain embodiments, the average diameter of the plurality of microcapsules is about 100 μm.

[0074] The epoxy resin can be any conventional epoxy resin. Exemplary epoxy resins include, but are not limited to, cresol-type novolac epoxy resins, phenol-type novolac epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol A-novolac epoxy resins, naphthalene epoxy resins, biphenyl epoxy resins, biphenyl aralkyl epoxy resins, polyacrylate epoxy resins, and combinations thereof. In certain embodiments, the epoxy resin includes bisphenol A epoxy resins and bisphenol F epoxy resins.

[0075] In certain embodiments, the dispersed matrix also comprises the partially cured epoxy resin formed by the reaction of epoxy resin and polyamines.In certain embodiments, the epoxy resin of 5-40mol%, 10-40mol%, 15-40mol%, 20-40mol%, 25-40mol%, 30-40mol%, 35-40mol%, 10-35mol%, 10-30mol%, 10-25mol%, 10-20mol%, 10-15mol%, 10-30mol% or 15-25mol% is cured by reacting with polyamines.In certain embodiments, the epoxy resin of about 20mol% is cured by reacting with polyamines.

[0076] In certain embodiments, the dispersed matrix further comprises one or more of a silica filler (eg, fumed silica), a polyamine curing agent, and a polythiol curing agent.

[0077] Exemplary polyamine curing agents include, but are not limited to, tetraethylenepentamine (TEPA), polyoxypropylenediamine, diethylenetriamine (DETA), isophoronediamine (IPDA), and 4,4'-methylenedianiline (MDA).

[0078] Exemplary polythiol curing agents include, but are not limited to, pentaerythritol tetrakis(3-mercaptopropionate) (PETMP), trimethylolpropane tris(3-mercaptopropionate) (TMPMP), ethylene glycol dimercaptoacetate (GDMA), and 1,2-ethanedithiol (EDT).

[0079] The present disclosure also provides a method of depositing the one-part adhesive composition described herein onto a substrate surface and curing the one-part adhesive composition to form a cured one-part adhesive composition.

[0080] The substrate is not particularly limited, and the present disclosure contemplates all substrates. In certain embodiments, the substrate comprises a metal, a metal alloy, a ceramic, a plastic, a wood, a concrete, an asphalt, a dry wall, a glass, and the like. Other exemplary substrates include, but are not limited to, low carbon steel, alloy steel, aluminum, and brass. In certain embodiments, the substrate is a threaded screw, a threaded nut, a threaded shaft, or a threaded bolt. In certain embodiments, the threaded component is a symmetrical trapezoidal thread, an asymmetrical trapezoidal thread, a circular thread, a rectangular thread, a triangular thread, a tapered thread, a cylindrical thread, a fine thread, a coarse thread, or a regular thread, or a combination thereof.

[0081] Curing the one-part adhesive composition may include subjecting the one-part adhesive composition to a temperature of 40-100° C., 50-100° C., 60-100° C., 70-100° C., 80-100° C., 90-100° C., 22-80° C., 22-95° C., 40-80° C., 40-95° C., or 80-95° C. The adhesive composition may be subjected to the curing temperature for 1-24 hours, 1-18 hours, 1-12 hours, 1-6 hours, 2-6 hours, 6-24 hours, 12-24 hours, or 18-24 hours.

[0082] In certain embodiments, curing the one-component adhesive composition comprises placing the one-component adhesive composition at 20-50°C, 30-50°C, or 35-45°C for 1-24 hours, 12-24 hours, or 12-18 hours; subsequently placing at 20-25°C for 1-24 hours, 6-24 hours, or 6-18 hours; and placing at 22-95°C, 40-95°C, or 80-95°C for 1-24 hours, 6-24 hours, 12-24 hours, or 18-24 hours. In certain embodiments, curing comprises placing the one-component adhesive composition at about 40°C for about 15 hours; subsequently placing at about 22°C for about 12 hours; and placing at about 80°C or about 95°C for about 24 hours.

[0083] The present disclosure also provides a cured one-component adhesive composition prepared according to the method described herein. The present disclosure also provides a threaded component, which also includes a cured one-component adhesive composition prepared according to the method described herein, wherein the cured one-component adhesive composition is disposed on at least one surface of the threaded component.

[0084] Select triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and The polyetheramine sold as T403 was demonstrated. It is critical to determine the stoichiometric ratio between the amine and the epoxy resin before conducting mechanical strength tests. This step ensures that a fully cured epoxy adhesive is produced. A study was conducted to determine the stoichiometric ratio of amine / epoxy resin in formulations based on TETA, TEPA, and various TEPA / T403 blends. By using differential scanning calorimetry (DSC), the glass transition temperature (T g ) as a function of amine concentration. At the stoichiometric epoxy / amine ratio, where crosslinking and chain interactions are at their peaks and segmental motion is at its lowest, the expected cure degree T g The value will reach the maximum value.

[0085] Figure 3A -E shows the T of different preparations gIt is noteworthy that small multifunctional amines such as TEPA and TETA, which have extremely high amine contents and lead to high cross-link density polymer networks, are characterized by their high T g However, when adding the long-chain amine T403 with a lower amine content, T g This decrease can be attributed to the lower crosslink density, which may contribute to the improved toughness to some extent.

[0086] Before moving on to formulating a one-component adhesive based on amine microcapsules, the threadlocking properties of a two-component amine / epoxy adhesive were first explored and initially validated. In this experimental setup, the liquid amine curing agent and epoxy adhesive were uniformly mixed according to standard operating procedures and then immediately applied to the bolt for adhesion testing. After the liquid mixture was applied, the bolt and nut were assembled to promote wetting and bonding of the two parts while the adhesive cured.

[0087] A range of amine / epoxy combinations were tested, all of which showed good adhesion properties (e.g. Figure 4 ). To cure epoxy resins, TEPA, TETA, and various TEPA / T403 combinations have been used. These amines themselves contain different numbers of reactive groups, resulting in network structures of various densities. In general, T403 is characterized by a lower amine content and longer molecular chains compared to TEPA and TETA, which have higher amine contents, which, when added in large quantities, can result in a significant reduction in crosslink density, thereby compromising threadlocking properties. In addition, due to its lower polarity, the reactivity of T403 is reduced, which can result in a less time-efficient curing process, which can adversely affect the mechanical properties and overall performance of the adhesive.

[0088] Temperature is an important factor affecting the strength of the cured product. Therefore, after assembling the bolts and nuts and preliminarily curing at room temperature for 12 hours, the samples were heated at room temperature, 40°C, 80°C and the T g (As shown in Figure 3), the epoxy adhesive was further cured at room temperature. The observations show that an increase in curing temperature can increase torque, indicating that there may be a correlation between curing temperature and the mechanical efficiency of the adhesive system. The above results preliminarily demonstrate the thread locking application of epoxy adhesives and pave the way for further detailed studies.

[0089] Based on the above observations, the efficacy of using epoxy adhesives for threadlocking applications has been demonstrated. Based on these findings, the amine composition 75TEPA25T403 was selected as a model for further formulation of amine microcapsule-based one-component adhesives for threadlocking applications. This means that the -NH molar ratios contributed by TEPA and T403 are 75% and 25%, respectively.

[0090] like Figure 5A-5D As shown, amine microcapsules were synthesized via interfacial polymerization to produce amine microcapsules with polyurea (PU) shells. These microcapsules are characterized by a tightly sealed core-shell structure that effectively encapsulates the core material and provides a barrier against external environmental factors. The excellent compactness and stability of the shell in the epoxy resin matrix help prevent leakage. Figure 6 The TGA results shown help determine the core polyamine content of the complete microcapsules, which is about 85 wt%. A thin, flexible shell is designed that cleverly surrounds the core material, achieving a balance between protection efficiency and performance. A thin, durable shell is designed that cleverly surrounds the core material, achieving a balance between protection and performance.

[0091] In the absence of solvents, it is not feasible to add film-forming polymers, which are essential for pre-applied threadlocking adhesives. Therefore, a solvent-free one-component adhesive for threadlocking applications has been proposed by incorporating amine-containing microcapsules into a partially cured epoxy resin. Partially curing the epoxy resin ensures that the adhesive film can be pre-applied to the screw surface, thereby achieving excellent surface dryness for long-term storage and creating a more user-friendly product for end users and manufacturers. In the case of such a pre-applied film, when tightening the screw, the resulting shear forces rupture these microcapsules, releasing the encapsulated amine curing agents. These curing agents then react with the epoxy matrix, triggering the polymerization process and bonding the surfaces of the screw and nut together.

[0092] In one example, 20% of the epoxy groups (according to amine blend 75TEPA25T403, the same chemistry as the microcapsule core) are pre-cured to achieve moderate surface dryness, with the remaining 80% being cured by the amine (75TEPA25T403) microcapsules during the adhesion process. These amine microcapsules serve a dual purpose: they function as both an encapsulant and a dry powder that increases the viscosity of the epoxy formulation. The resulting increased viscosity restricts the flow and spread of the mixture, allowing for thicker, more controlled handling. The inherently rough texture of the amine microcapsules provides the added benefit of making the cured surface less tacky and improving the tactile experience for the user.

[0093] The process involves applying an uncured liquid epoxy mixture to the surface of the M10 hexagonal bolt screw and controlling the film thickness, followed by a surface drying process. Temperature and duration are key variables that affect the curing and drying process. Figure 7The adhesive mixture is shown with different drying times at 40°C according to ISO 9117-5. The drying test requires the adhesive to be applied to a glass sheet on which a piece of paper is placed. A 20g weight is then added to the paper. The test piece is then tapped to determine if the paper can fall off. The results show that after 9 hours of curing, the sample is still sticky and the test paper cannot fall off. After 12 hours of curing, the sample begins to harden but still feels "sticky". After 36 hours of curing, it is completely dry and hard to the touch. Figure 8 The surface of a bolt screw is shown after the adhesive mixture has cured for 15 hours. At this stage, the surface is not sticky, with only some flakes falling off, making it ready for further storage or testing.

[0094] After achieving moderate surface dryness, the product is ready for long-term storage or immediate application. During application, the threaded bolt screws are inserted into the nuts at ambient temperature and allowed to rest for 12 hours. It is assumed that during this stage, the microcapsules rupture, thereby releasing their contents to interact with the epoxy mixture and stimulate other chains to interact. After the rest period, the screws are further subjected to a curing procedure at different temperatures (room temperature, 40°C, 80°C, 95°C) for a longer period of 24 hours. This procedure is designed to enhance the mechanical properties, dimensional stability and bonding characteristics of the epoxy resin, thereby optimizing its performance and versatility.

[0095] The size of the microcapsules has an important influence on the effectiveness of the adhesive. The loosening torque test was carried out on microcapsules of different sizes and epoxy resin. The results are as follows Fig. 9As shown. The microcapsules used in this study ranged in size from 50μm to 300μm, and all microcapsules showed the possibility of rupture during the tightening of the nut. The loosening torque results at different temperatures are as follows: at room temperature, 50μm produced 6.78Nm, 100μm produced 6.80Nm, 200μm produced 3.28Nm, and 300μm produced 12.42Nm. At 40°C, the respective results were 10.43Nm, 9.80Nm, 4.74Nm, and 19.80Nm. At 80°C, the respective results were 27.06Nm, 28.86Nm, 21.83Nm, and 23.64Nm. At 95°C, the values ​​were 23.76Nm, 24.37Nm, 24.26Nm, and 24.54Nm, respectively. It is worth noting that the 100μm microcapsules showed excellent performance on average. Larger microcapsules, despite their higher core content, tend to break during screw bonding and fail to distribute evenly in the epoxy matrix. Conversely, smaller microcapsules promote more even distribution of the amine in the epoxy mixture, but are limited by lower core content and thicker walls, which may leave more residual polyurea shell. Importantly, curing temperatures exceeding 80°C lead to substantial improvements. The added thermal energy at these higher temperatures speeds up the curing process and enhances crosslinking in the epoxy, improving its mechanical properties and adhesion.

[0096] This research focuses on improving the rest and cure durations in a specific manufacturing method. The goal is to increase productivity and speed up the entire process while maintaining the quality, integrity and performance of the final product.

[0097] Fig.10 The experimental method is shown to maintain a temperature of 40°C for 15 hours. At the same time, the resting time was significantly reduced from 12 hours to 2 hours, and the curing time was reduced from 24 hours to 6 hours or 2 hours. The experimental results show that different torques were measured at different temperature conditions for a 2-hour resting period followed by a 2-hour curing period. The torque values ​​recorded were: 4.78Nm at room temperature (RT), 5.30Nm at 40°C, 21.54Nm at 80°C, and 20.24Nm at 95°C. Keeping the resting time at 2 hours and extending the curing time to 6 hours, the torque values ​​increased: 6.06Nm at RT, 11.96Nm at 40°C, 30.02Nm at 80°C, and 24.25Nm at 95°C. These results highlight that the performance can be improved by strategically reducing the resting period and curing period to 2 hours and 6 hours, respectively. This enhancement is particularly evident during the 80°C cure process, where the torque achieved by the one-component adhesive with 80MC20 curing agent (30.02 Nm) is very close to the torque value of the pure curing agent two-component adhesive (37.1 Nm).

[0098] This evidence suggests that process efficiency and product quality can be not only maintained but even improved with significantly reduced stand and cure times. Furthermore, the one-component adhesives performed comparable to two-component systems, especially when cured at elevated temperatures, highlighting the significant benefits of using one-component adhesives. These benefits include at least one of the following: streamlined production processes, reduced risk of mixing errors, and increased production efficiency, especially in high-throughput manufacturing scenarios. Therefore, the results of this study provide a promising avenue for the future use of one-component adhesives in a variety of industry applications.

[0099] Example

[0100] To prepare amine-containing microcapsules, TEPA (75 wt%) and The T403 (25 wt%) liquid mixture was directly injected into the continuous phase through the microfluidic device. The outlet of the microtube was located below the surface of the solution, close to the periphery of the impeller. While injecting, the continuous phase was stirred with an impeller at a speed of 500 rpm. The continuous phase (50.0 g) was prepared by mixing with H 12 The system was made up of paraffin oil dissolved in MDI. After 20 minutes of injection, the system was allowed to react at 40°C for 6 hours. Then the reaction was stopped. The amine microcapsules with PU shells were washed 5 times with n-hexane, dried in a fume hood for 20 minutes, and then collected.

[0101] To prepare the solvent-free one-component adhesive, 3 g of PU-75TEPA25T403, 0.15 g of fumed silica, 0.6 g of 75TEPA25T403 liquid mixture and 10 g of EPOLAM 5015 epoxy resin were uniformly mixed. The screws were first cleaned with acetone to eliminate any dirt or potential contaminants that could interfere with the bonding process. The surface of the screws was then coated by dipping the screws into the mixture. The samples were then left at room temperature for 12 hours to allow the mixture to cure and reach a medium surface dry state. Subsequently, the threaded bolts were screwed into the nuts at room temperature. The samples were then left at room temperature for another 12 hours. The curing process lasted for 24 hours at 40°C, which allowed the threaded components to be fully tightened.

Claims

1. A one-component adhesive composition comprising a plurality of microcapsules and a dispersion matrix, wherein each of the plurality of microcapsules comprises a core and a shell at least partially surrounding the core, wherein the core comprises a polyamine, the shell comprises a cross-linked polyurea, and the dispersion matrix comprises an epoxy resin. 2 . The one-component adhesive composition according to claim 1 , wherein the average diameter of the plurality of microcapsules is 10-300 μm.

3. The one-component adhesive composition of claim 1, wherein the polyamine comprises a polyalkylamine, a polyetheramine, a polyarylamine or a mixture thereof.

4. The one-component adhesive composition according to claim 1, wherein the polyamine comprises triethylenetetramine (TETA), tetraethylenepentamine (TEPA), polyoxypropylenetriamine or a mixture thereof, wherein the polyoxypropylenetriamine is represented by the following formula: Wherein m+n+p is 5 to 6.

5. The one-component adhesive composition of claim 1, wherein the crosslinked polyurea comprises a polyamine crosslinked with a diisocyanate, a polyisocyanate, or a mixture thereof.

6. The one-component adhesive composition of claim 1, wherein the crosslinked polyurea comprises a polyamine crosslinked with 4,4'-dicyclohexylmethane diisocyanate.

7. The one-component adhesive composition of claim 4, wherein the polyamine comprises TETA, TEPA, or TEPA and polyoxypropylene triamine.

8. The one-component adhesive composition of claim 4, wherein the polyamine comprises TEPA and polyoxypropylene triamine, wherein the molar ratio of the TEPA to the amine in the polyoxypropylene triamine is 1:3 to 3:1, respectively.

9. The one-component adhesive composition of claim 1, wherein the epoxy resin comprises bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, novolac epoxy resin, alicyclic epoxy resin, glycidyl ester epoxy resin, glycidyl ether resin, glycidyl amine epoxy resin, halogenated epoxy resin or a mixture thereof.

10. The one-component adhesive composition according to claim 1, wherein the epoxy resin comprises a bisphenol A type epoxy resin and a bisphenol F type epoxy resin.

11. The one-component adhesive composition according to claim 1, wherein the polyamine comprises triethylenetetramine (TETA), tetraethylenepentamine (TEPA), polyoxypropylenetriamine or a mixture thereof, wherein the polyoxypropylenetriamine is represented by the following formula: Where m+n+p is 5 to 6; The crosslinked polyurea comprises a polyamine crosslinked with 4,4′-dicyclohexylmethane diisocyanate; The epoxy resin includes bisphenol A epoxy resin and bisphenol F epoxy resin. 12 . The one-component adhesive composition according to claim 11 , wherein the plurality of microcapsules and the dispersion matrix are present in a mass ratio of 3:17 to 1:3, respectively.

13. The one-component adhesive composition of claim 11, wherein the dispersed matrix further comprises a partially cured epoxy resin formed by a reaction of the epoxy resin and the polyamine.

14. The one-component adhesive composition of claim 13, wherein 10-30 mol% of the epoxy resin in the dispersed matrix reacts with the polyamine.

15. The one-component adhesive composition according to claim 1, wherein the epoxy resin further comprises a polyamine curing agent, a polythiol curing agent or a mixture thereof.

16. The one-component adhesive composition of claim 11, wherein the plurality of microcapsules and the dispersed matrix are present in a mass ratio of about 1:4, respectively; and the dispersed matrix further comprises a partially cured epoxy resin formed by a reaction of the epoxy resin and the polyamine, wherein 10-30 mol % of the epoxy resin in the dispersed matrix reacts with the polyamine.

17. The one-component adhesive composition of claim 16, wherein the polyamine comprises TEPA and polyoxypropylene triamine, wherein the molar ratio of TEPA to the amine in the polyoxypropylene triamine is about 3: about 1, respectively.

18. A method comprising depositing the one-part adhesive composition of claim 1 onto a surface of a substrate and curing the one-part adhesive composition to form a cured one-part adhesive composition.

19. The method of claim 18, wherein the substrate comprises a threaded component.

20. The method of claim 18, wherein curing comprises subjecting the one-component adhesive composition to 25-100°C for 1-24 hours.

21. The method of claim 18, wherein curing comprises subjecting the one-component adhesive composition to 35-55°C for 1-24 hours, 20-25°C for 1-24 hours, 40-100°C for 1-24 hours.

22. A cured one-component adhesive composition prepared according to the method of claim 18.

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