A fast wet-state bonding formaldehyde-free adhesive, a preparation method and application thereof
By constructing a cross-linking network through the pre-cross-linking and fast solvent exchange mechanism of the solvent-resin system, the problems of slow reaction and poor water resistance of underwater adhesives are solved, achieving a fast and high-strength bonding effect suitable for various environments and materials.
Patent Information
- Application Number
- CN202610550897.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-24
- Publication Date
- 2026-06-12
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer adhesive preparation technology, and in particular to a formaldehyde-free adhesive based on a solvent exchange curing mechanism, suitable for rapid bonding in humid or underwater environments, and its preparation method. Background Technology
[0002] Adhesives are crucial materials in furniture manufacturing, composite material production, and component repair, and their consumption is enormous. To reduce the health hazards of traditional aldehyde-based adhesives, the development of high-performance formaldehyde-free wood adhesives has become an urgent industry need.
[0003] The wood industry consumes more than three-quarters of all adhesives, making it an indispensable part of modern industry. In actual production, to reduce the impact of wood shrinkage and swelling on product quality and to prevent "dry board" failure caused by dry wood absorbing adhesive, it is often necessary to glue wood with high moisture content. However, compared with dry environments, wet bonding faces two major challenges: first, the barrier effect of the water interface layer hinders effective contact between the adhesive and the substrate; second, water molecules easily penetrate the adhesive itself, causing swelling and structural damage, resulting in poor water resistance of ordinary adhesives and difficulty in achieving reliable bonding in humid or underwater environments, which greatly limits the performance improvement and application expansion of wood and its composite materials.
[0004] Current underwater adhesives mainly suffer from the following limitations: Traditional epoxy resin or polyurethane systems rely on underwater chemical cross-linking for curing, resulting in slow reactions and insufficient initial strength after curing; another type of adhesive based on dynamic non-covalent interactions such as hydrogen bonding and coordination can achieve rapid interfacial adhesion, but suffers from low bulk strength and poor water resistance and durability; while introducing hydrophobic structural domains or constructing oleogel systems can improve water resistance, they often weaken the bulk strength of the adhesive layer. Furthermore, rapid underwater adhesives designed based on polyphenol chemistry, eutectic solvents, or nano-drainage structures generally face problems such as high raw material costs, complex formulations, and cumbersome preparation processes, limiting their applicability.
[0005] Therefore, developing a formaldehyde-free wood adhesive suitable for high-humidity environments and capable of achieving high-strength bonding quickly is of significant scientific research value and engineering application importance. Summary of the Invention
[0006] To address the technical problems existing in the prior art, this invention provides a rapid wet bonding formaldehyde-free adhesive, its preparation method, and its application. The adhesive of this invention utilizes a specific solvent-resin system, through a mechanism combining pre-crosslinking in a good solvent and rapid solvent exchange in a poor solvent, to achieve rapid and strong bonding in humid, underwater, and even various liquid environments.
[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0008] On the one hand, this invention provides a rapid wet-state bonding formaldehyde-free adhesive, the core of which lies in the construction of a cross-linking network under good solvent conditions and solvent exchange-dominated adhesive layer curing. This adhesive is prepared from the following components by weight: 15–30 parts resin matrix, 70–85 parts polar aprotic solvent, and 5–15 parts multifunctional epoxy cross-linking agent;
[0009] Furthermore, the resin matrix is an olefin-maleic anhydride alternating copolymer with a molecular weight of 200 kDa or higher. The backbone of this type of copolymer is composed of alternating hydrophobic olefin units and highly reactive anhydride units, providing the necessary hydrophobicity and reactive sites. Preferably, the olefin-maleic anhydride alternating copolymer is an isobutylene-maleic anhydride copolymer, an ethylene-maleic anhydride copolymer, or a methyl vinyl ether-maleic anhydride copolymer.
[0010] The polar aprotic solvent is selected from dimethyl sulfoxide or sulfolane; its key functions are: first, to fully dissolve the copolymer as a good solvent; second, to act as a Lewis base and reversibly interact with the anhydride groups in the copolymer, thus playing a dual role of protecting and activating the anhydride, which not only avoids premature hydrolysis of the anhydride in an aqueous environment, but also enhances its reactivity with epoxy groups.
[0011] The multifunctional epoxy crosslinking agent is used to react with the anhydride-activated copolymer to construct a moderately crosslinked prepolymer network in the solvent system. This pre-crosslinked network ensures that the adhesive has a suitable initial viscosity and forms a strong bulk structure during subsequent phase transitions. Preferably, it is a high-functionality epoxy compound such as 4,4'-diaminodiphenylmethane tetraglycidylamine (TGDDM), triglycidyl isocyanate (TGIC), triglycidylamine (TGA), epoxy resin E44, epoxy resin E51, epoxidized soybean oil, or epoxidized castor oil.
[0012] The mass ratio of the resin matrix to the multifunctional epoxy crosslinking agent is 1:(0.25–0.75).
[0013] On the other hand, the present invention also provides a method for preparing the above-mentioned rapid wet bonding formaldehyde-free adhesive, comprising the following steps:
[0014] (1) Under the condition of isolating water vapor, the resin matrix is dissolved in the polar aprotic solvent and mechanically stirred. After complete dissolution, a colorless to pale yellow clear solution is obtained and sealed and stored under the condition of isolating water vapor.
[0015] (2) Under the condition of isolating water vapor, the copolymer solution obtained in step (1) is mixed with the multifunctional epoxy crosslinking agent and mechanically stirred to disperse it evenly. Let it stand for more than 30 minutes to allow the crosslinking reaction to proceed completely, and a fast wet bonding formaldehyde-free adhesive is obtained.
[0016] Furthermore, this invention also provides an application of the above-mentioned rapid wet bonding formaldehyde-free adhesive for bonding substrates under conditions of air, water, oil, ethanol, and salt solvents. The substrate is wood, metal, or plastic. Preferably, the metal is iron, aluminum, or copper; the plastic is polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), or polytetrafluoroethylene (PTFE).
[0017] This invention relates to a rapid wet-state bonding formaldehyde-free adhesive. When in air, the polar aprotic solvent evaporates, and the resin prepolymer network formed by the resin matrix and the multifunctional epoxy crosslinking agent precipitates from the solution. It shrinks in volume and tightly wraps around the microscopic protrusions on the substrate surface. The unreacted acid anhydrides, epoxy groups, and polar units on the polymer chains in the precipitated adhesive layer can form hydrogen bonds, ionic-π interactions, and other multi-level interactions with the substrate surface, and continue to undergo a curing reaction with its own network to achieve bonding to the substrate.
[0018] This invention provides a rapid wet-state bonding formaldehyde-free adhesive that achieves underwater adhesion in unfavorable solvents such as water, oil, ethanol, and salt solutions through rapid solvent exchange. When the adhesive is coated or injected into the interface of an unfavorable solvent, the polar aprotic solvent, acting as a favorable solvent, rapidly diffuses from the interior of the adhesive into the unfavorable solvent environment, inducing rapid phase separation. During curing, the polar aprotic solvent rapidly diffuses from the interior of the adhesive to the interface layer, displacing the interface layer while the resin prepolymer network precipitates from the solution, shrinks in volume, and tightly wraps around the microscopic protrusions on the substrate surface. This allows for the formation of a tough adhesive layer with excellent cohesive strength and interfacial adhesion in water, oil, ethanol, and salt solutions.
[0019] Compared with the prior art, the present invention has the following beneficial effects:
[0020] (1) This invention provides a fast wet bonding formaldehyde-free adhesive that avoids the damage to the hydrophobic and tough structures of isobutylene-maleic anhydride caused by conventional alkaline hydrolysis. The adhesive is cured underwater through rapid solvent exchange. Based on the rapid solvent exchange physical process, it can achieve the removal of interfacial water and the establishment of initial adhesion within seconds to minutes, solving the problem of slow underwater curing of traditional chemical reaction adhesives.
[0021] (2) The pre-crosslinking network and subsequent curing of the present invention endow the adhesive layer with high cohesive strength; the hydrophobic structure of the resin itself and the dense crosslinking network ensure the excellent water resistance of the adhesive layer after curing.
[0022] (3) The curing mechanism of the present invention does not depend on a specific chemical reaction, has excellent environmental / substrate adaptability, and can be used for bonding in underwater, oily, high humidity and even various organic solvent environments. It also has good bonding effect on dry or wet surfaces of various materials such as wood, metal, ceramics and plastics.
[0023] (4) The solvent exchange mechanism of the present invention is highly compatible with the porous structure of wood; DMSO can partially penetrate into the wood ducts, accelerate local exchange, and make the adhesive better anchored inside the wood to achieve "conformal bonding", which is very suitable for rapid cold pressing or hot pressing of wood or artificial board with high moisture content. Detailed Implementation
[0024] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with specific embodiments.
[0025] Unless otherwise specified, all reagents and materials used in this invention are commercially available. Specifically, isobutylene-maleic anhydride copolymer was purchased from Kuraray International Trading (Shanghai) Co., Ltd., with molecular weights of 6 kDa, 20 kDa, 100 kDa, 150 kDa, 200 kDa, and 300 kDa; ethylene-maleic anhydride copolymer (polyethylene-grafted maleic anhydride) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with molecular weights of 100–500 kDa and 500 kDa; and methyl vinyl ether-maleic anhydride copolymer (polymethyl vinyl ether maleic anhydride) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with molecular weights of 130–200 kDa and 300 kDa.
[0026] This invention provides a rapid wet bonding formaldehyde-free adhesive, its preparation method, and its application. Specific embodiments are as follows.
[0027] Example 1
[0028] A method for preparing a rapid wet-bonding formaldehyde-free adhesive includes the following steps:
[0029] Step 1: Under sealed conditions, dissolve 20g of isobutylene-maleic anhydride copolymer (molecular weight 300kDa) in 80g of dimethyl sulfoxide and mechanically stir (stirring speed 500 rpm, stirring time 30 min, stirring temperature 30℃) until the adhesive is completely dissolved to obtain a colorless to pale yellow clear solution.
[0030] Step 2: Under conditions of complete moisture isolation, mix the copolymer solution obtained in Step 1 with 5 g of 4,4-diaminodiphenylmethane tetraglycidylamine and mechanically stir (stirring speed 500 rpm, stirring time 30 min, stirring temperature 30℃) to ensure uniform dispersion. Allow the mixture to stand for at least 30 min under conditions of complete moisture isolation to allow the crosslinking reaction to proceed completely. This yields a rapid wet-bonding formaldehyde-free adhesive.
[0031] The inventors tested the shear strength of the prepared rapid wet bonding formaldehyde-free adhesive after curing in different solvents. The specific process is as follows.
[0032] The wood substrates were placed in tap water (25℃), tap water (80℃), saturated sodium chloride solution, silicone oil, and anhydrous ethanol, respectively. The prepared adhesive was then applied to the wood substrates at a rate of 240 g / m². Another substrate was then overlapped onto the adhesive and secured with dovetail clips. After curing for 5 minutes, the substrates were removed and their shear strength was tested.
[0033] The shear strength of the adhesive prepared in Example 1 in different solvents was tested, and the results are shown in Table 1.
[0034] Table 1
[0035]
[0036] As shown in Table 1, the adhesive prepared by the present invention can be cured rapidly in a variety of solvents, and has high shear strength after curing in a short time (5 min), thus realizing the rapid bonding of the adhesive in a variety of solvents.
[0037] Artificial boards were prepared using the adhesive from Example 1 at different hot-pressing temperatures. The hot-pressing pressure was 1 MPa, the time was 6 min, and the adhesive application rate was 200 g / m². 2 According to GB / T 17657–2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels", the strength and boiling water strength of the prepared wood-based panels were tested, and the results are shown in Table 2.
[0038] Table 2
[0039]
[0040] As shown in Table 2, the engineered wood panels prepared using the adhesive of the present invention can be cured in a short time (6 min) at different hot pressing temperatures, and the strength and boiling water strength after curing are both high.
[0041] Example 2
[0042] In this embodiment, the amount of 4,4-diaminodiphenylmethane tetraglycidylamine used was 10 g, and the other conditions were the same as in Example 1.
[0043] The shear strength of the adhesive prepared in Example 1 in different solvents was tested using the same method as in Example 1, and the results are shown in Table 3. Compared with Example 1, under the same conditions, reducing the amount of 4,4-diaminodiphenylmethane tetraglycidylamine resulted in a decrease in the shear strength of the prepared adhesive in all liquids.
[0044] Table 3
[0045]
[0046] Artificial boards were prepared using the adhesive from Example 2 at different hot-pressing temperatures. The hot-pressing pressure was 1 MPa, the time was 6 min, and the adhesive application rate was 200 g / m². 2 The wet strength and boiling water strength of the prepared artificial board were tested, and the results are shown in Table 4. At different hot-pressing temperatures, both the wet strength and boiling water strength decreased compared to Example 1.
[0047] Table 4
[0048]
[0049] Example 3
[0050] In this embodiment, the amount of 4,4-diaminodiphenylmethane tetraglycidylamine used was 15 g, and the other conditions were the same as in Example 1.
[0051] The shear strength of the adhesive prepared in Example 3 in different solvents was tested using the same method as in Example 1, and the results are shown in Table 5.
[0052] Table 5
[0053]
[0054] Artificial boards were prepared using the adhesive from Example 3 at different hot-pressing temperatures. The hot-pressing pressure was 1 MPa, the time was 6 min, and the adhesive application rate was 200 g / m². 2 The strength and boiling water strength of the prepared artificial boards were tested, and the results are shown in Table 6.
[0055] Table 6
[0056]
[0057] As shown in Tables 5–6, the increasing concentration of 4,4-diaminodiphenylmethane tetraglycidylamine leads to poorer adhesive properties in the prepared adhesive grade. This is because the higher concentration of 4,4-diaminodiphenylmethane tetraglycidylamine results in incomplete reaction and poorer adhesive properties.
[0058] Example 4
[0059] In this embodiment, 4,4-diaminodiphenylmethane tetraglycidylamine was replaced with an equal mass of epoxy resin E44, and the other conditions were the same as in Example 1.
[0060] Example 5
[0061] In this embodiment, 4,4-diaminodiphenylmethane tetraglycidylamine was replaced with an equal mass of epoxy resin E51, and the other conditions were the same as in Example 1.
[0062] Example 6
[0063] In this embodiment, 4,4-diaminodiphenylmethane tetraglycidylamine was replaced with an equal mass of triglycidylamine (TGA), and the other conditions were the same as in Example 1.
[0064] Example 7
[0065] In this embodiment, 4,4-diaminodiphenylmethane tetraglycidylamine was replaced with an equal mass of epoxidized soybean oil, and the other conditions were the same as in Example 1.
[0066] Example 8
[0067] In this embodiment, 4,4-diaminodiphenylmethane tetraglycidylamine was replaced with an equal mass of triglycidyl isocyanurate (TGIC), and the other conditions were the same as in Example 1.
[0068] Example 9
[0069] In this embodiment, 4,4-diaminodiphenylmethane tetraglycidylamine was replaced with an equal mass of epoxidized castor oil, and the other conditions were the same as in Example 1.
[0070] Example 10
[0071] In this embodiment, the isobutylene-maleic anhydride copolymer was replaced with an equal mass of ethylene-maleic anhydride copolymer (molecular weight 500 kDa), and the other conditions were the same as in Example 1.
[0072] Example 11
[0073] In this embodiment, the isobutylene-maleic anhydride copolymer was replaced with an equal mass of methyl vinyl ether-maleic anhydride copolymer (molecular weight 300kDa), and the other conditions were the same as in Example 1.
[0074] Example 12
[0075] In this embodiment, the molecular weight of the isobutylene-maleic anhydride copolymer is 200 kDa, and the other conditions are the same as in Example 1.
[0076] The shear strength of the adhesives prepared in Examples 4–12 above in different solvents was tested using the same method as in Example 1, and the results are shown in Table 7.
[0077] Table 7
[0078]
[0079] As shown in Table 7, the adhesives prepared in the embodiments of the present invention have high shear strength in different solvents.
[0080] Artificial boards were prepared using the adhesives from Examples 4–12 at different hot-pressing temperatures. The hot-pressing pressure was 1 MPa, the time was 6 min, and the adhesive application rate was 200 g / m². 2 The strength and boiling water strength of the prepared artificial boards were tested, and the results are shown in Table 8.
[0081] Table 8
[0082]
[0083] As shown in Tables 7–8, different resin matrices and multifunctional epoxy crosslinking agents specified in this invention can all produce adhesives with strong bonding ability.
[0084] The present invention also applies the adhesive prepared in the examples to different substrates, with a coating amount of 200 g / m². 2 Then, the same substrate was overlapped onto the adhesive and fixed with dovetail clips. After curing in an oven at 120°C for 1 hour, the shear strength was tested. The shear strength of the rapid wet-bonding formaldehyde-free adhesive prepared using the above method against different substrates is shown in Table 9.
[0085] Table 9
[0086]
[0087] As shown in Table 9, the adhesive prepared by this invention can bond various substrates (wood, iron, aluminum, copper) and has high short-time shear strength.
[0088] Different substrates were placed in tap water (temperature 25℃), and then the prepared adhesive was applied to the substrates at a coating amount of 240 g / m². 2 Then, using the same substrate, the adhesive was overlapped and fixed with dovetail clips. After curing for 5 minutes, it was removed and the shear strength of the adhesive on different substrates after underwater curing was tested. The results are shown in Table 10.
[0089] Table 10
[0090]
[0091] As shown in Table 10, the adhesive of this application has good bonding effect on different substrates after short-term underwater curing.
[0092] To further illustrate the beneficial effects of the present invention, the following comparative examples were constructed.
[0093] Comparative Example 1
[0094] In this comparative example, step 2 is omitted, and the remaining conditions are the same as in Example 1.
[0095] Comparative Example 2
[0096] In this comparative example, the molecular weight of the isobutylene-maleic anhydride copolymer is 6 kDa, and the other conditions are the same as in Example 1.
[0097] Comparative Example 3
[0098] In this comparative example, the molecular weight of the isobutylene-maleic anhydride copolymer is 20 kDa, and the other conditions are the same as in Example 1.
[0099] Comparative Example 4
[0100] In this comparative example, the molecular weight of the isobutylene-maleic anhydride copolymer is 100 kDa, and the other conditions are the same as in Example 1.
[0101] Comparative Example 5
[0102] In this comparative example, the molecular weight of the isobutylene-maleic anhydride copolymer is 150 kDa, and the other conditions are the same as in Example 1.
[0103] Comparative Example 6
[0104] In this comparative example, 4,4-diaminodiphenylmethane tetraglycidylamine was replaced with an equal mass of soybean oil, and the other conditions were the same as in Example 1.
[0105] Comparative Example 7
[0106] In this comparative example, the molecular weight of the methyl vinyl ether-maleic anhydride copolymer is 130–200 kDa, and the other conditions are the same as in Example 11.
[0107] The shear strength of the adhesives prepared in Comparative Examples 1–7 in different solvents was tested using the same method as in Example 1, and the results are shown in Table 11.
[0108] Table 11
[0109]
[0110] As shown in Table 11, compared with the examples, the shear strength of the adhesives prepared in the comparative examples after curing in tap water (temperature 25°C), tap water (80°C), saturated sodium chloride solution, silicone oil, and anhydrous ethanol was significantly reduced. Furthermore, in Comparative Examples 2–4, the isobutylene-maleic anhydride copolymer had a low molecular weight and could not achieve wood bonding in 80°C hot water.
[0111] Artificial boards were prepared using adhesives from Comparative Examples 1–7 at different hot-pressing temperatures. The hot-pressing pressure was 1 MPa, the time was 6 min, and the adhesive application rate was 200 g / m². 2 The strength and boiling water strength of the prepared artificial boards were tested according to GB / T 17657–2022, and the results are shown in Table 12.
[0112] Table 12
[0113]
[0114] As shown in Table 12, the wet strength and boiling water strength of the adhesives prepared in the comparative examples were significantly lower than those in the examples at different hot-pressing temperatures. Furthermore, the adhesives of comparative examples 2–3 could not achieve bonding of the engineered wood panels at different hot-pressing temperatures, regardless of whether wet strength or boiling water strength was tested, and they would directly delaminate.
[0115] The present invention also applies the adhesives prepared in Comparative Examples 1–7 to different substrates, with a coating amount of 200 g / m². 2 Then, the same substrate was overlapped onto the adhesive and fixed with dovetail clips. After curing in a 120°C oven for 1 hour, the shear strength was tested. The shear strength of the rapid wet-bonding formaldehyde-free adhesive prepared using the above method against different substrates is shown in Table 13.
[0116] Table 13
[0117]
[0118] As shown in Table 13, after curing at 120°C, the adhesive prepared in the comparative examples showed a significant decrease in bonding strength to different substrates compared to the examples. Comparative examples 2–3 only showed a certain bonding effect on wood.
[0119] The shear strength of the adhesives prepared in Comparative Examples 1–7 after underwater curing on different substrates was tested, and the results are shown in Table 14.
[0120] Table 14
[0121]
[0122] As shown in Table 14, the shear strength of the adhesives prepared in Comparative Examples 1–7 after underwater curing on different substrates was significantly lower than that in the Examples.
[0123] In summary, the adhesive of this invention utilizes a specific solvent-resin system, through a mechanism combining pre-crosslinking in a good solvent and rapid solvent exchange in a poor solvent, to achieve rapid and strong bonding of different substrates in humid, underwater, and even various liquid environments.
[0124] The above description is a preferred embodiment of the present invention. For those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.
Claims
1. A fast-wet bonding formaldehyde-free adhesive, characterized in that, It is prepared from the following components in parts by weight: 15–30 parts resin matrix, 70–85 parts polar aprotic solvent, and 0.75–6 parts multifunctional epoxy crosslinking agent. The resin matrix is an olefin-maleic anhydride alternating copolymer with a molecular weight of 200 kDa or higher; the polar aprotic solvent is dimethyl sulfoxide or sulfolane; the multifunctional epoxy crosslinking agent is 4,4'-diaminodiphenylmethane tetraglycidylamine, triglycidyl isocyanurate, triglycidylamine, epoxidized soybean oil, or epoxidized castor oil; wherein the mass ratio of the resin matrix to the multifunctional epoxy crosslinking agent is 1:0.25–0.
75.
2. The rapid wet-bonding formaldehyde-free adhesive according to claim 1, characterized in that, The olefin-maleic anhydride alternating copolymer is isobutylene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, or methyl vinyl ether-maleic anhydride copolymer.
3. The method for preparing the rapid wet-state bonding formaldehyde-free adhesive according to claim 1 or 2, characterized in that, Includes the following steps: S1: Under conditions that prevent moisture from entering the body, dissolve the resin matrix in a polar aprotic solvent, stir mechanically until completely dissolved, and obtain a colorless to pale yellow clear solution. Store it in a sealed container under conditions that prevent moisture from entering the body. S2: Under the condition of isolating water vapor, mix the solution of S1 with the multifunctional epoxy crosslinking agent, mechanically stir to make it evenly dispersed, and let it stand for more than 30 minutes to allow the crosslinking reaction to be completed, and obtain a fast wet bonding formaldehyde-free adhesive.
4. The preparation method according to claim 3, characterized in that, In S1 and S2, the mechanical stirring speed is 300–600 rpm, the stirring time is 15–30 min, and the stirring temperature is 20–40℃.
5. The preparation method according to claim 4, characterized in that, In S2, the settling temperature is 20–30°C.
6. The application of the rapid wet bonding formaldehyde-free adhesive according to claim 1 or 2, characterized in that, Used for bonding substrates in air, water, oil, ethanol or salt solvents.
7. The application according to claim 6, characterized in that, The substrate is wood, metal, or plastic.
8. The application according to claim 7, characterized in that, The metal is iron, aluminum, or copper.
9. The application according to claim 7, characterized in that, The plastic is PE, PMMA, PP or PTFE.