Eco-friendly degradable thermosetting adhesive based on dynamic crosslinking of poly(β-amino ester) and preparation method therefor

Abstract

The present invention relates to: an eco-friendly degradable thermosetting adhesive based on dynamic crosslinking of poly(β-amino ester), the adhesive being characterized by synthesis and curing through a transesterification reaction activated by β-amine under mild conditions due to an internal catalytic effect without using an external catalyst; and a preparation method for the eco-friendly degradable thermosetting adhesive. According to the present invention, when an adhesive comprising a dynamically crosslinked poly(β-amino ester) (PBAE CANs) is applied, reprocessing is possible while maintaining high adhesion between two heterogeneous interfaces, thereby enabling recycling.

Description

Poly(β-amino ester) dynamic crosslinking-based eco-friendly biodegradable thermosetting adhesive and method for manufacturing the same

[0001] The present invention relates to an eco-friendly biodegradable thermosetting adhesive based on a dynamic crosslinking of poly(β-amino ester) and a method for manufacturing the same. Specifically, the invention relates to an eco-friendly biodegradable thermosetting adhesive based on a dynamic crosslinking of poly(β-amino ester) and a method for manufacturing the same, characterized in that β-amine activates the ester exchange reaction and is synthesized and cured by an exchange reaction under mild conditions using an internal catalytic effect without using an external catalyst.

[0002]

[0003] Unlike traditional physical bonding methods such as screws and welding, adhesives are polymer mixtures capable of bonding various materials and surfaces without damage. Unlike physical bonding, which concentrates stress only at the connected areas, chemical bonding using adhesives disperses stress and reduces load, thereby minimizing the possibility of bonding failure.

[0004] Therefore, adhesives enable adhesion between various materials, so they can be widely used in various industrial fields such as automobiles and electronic devices. These advantages make adhesives an essential material in the overall industrial sector, and as a result, the size of the global adhesive market is continuously growing. Consequently, there is a need for technological development to meet this demand, and various technologies such as those described in Patent Documents 1 to 3 are being developed and patented.

[0005] Two-part adhesives, which are widely used recently, are adhesives made primarily using thermosetting polymers. They are cured through a chemical reaction between a base and a curing agent to form a strong bond. This curing process is irreversible and has the characteristic that once cured, it does not melt or reform.

[0006] In other words, two-component adhesives provide high adhesion by forming a chemical bond through the mixing of two components, a base and a curing agent. As a thermosetting adhesive, it has excellent heat resistance and chemical resistance. Since curing does not begin until the two parts are mixed, it can be applied with sufficient time, and it has the advantage of being able to control properties such as curing speed and adhesion by mixing in various ratios or adding additives.

[0007] However, two-component adhesives are thermosetting polymers that do not have flowability once a cross-linked structure is formed, making physical reprocessing impossible. Although they have high chemical resistance, they do not dissolve in various solvents, making it difficult to separate heterogeneous interfaces and difficult to remove adhesive residues. Consequently, there is a problem in that it is very difficult to recycle materials with such adhesive residues.

[0008] Recently, Covalent Adaptable Networks (CANs) have been attracting attention as a solution to overcome the disadvantages of thermosetting polymer-based adhesives, as they have a cross-linked molecular structure similar to thermosetting polymers but possess reprocessability through dynamic exchange reactions under specific conditions.

[0009] CANs are capable of dynamic exchange reactions through external stimuli such as heat, light, and pH, and thus possess the characteristic of being reprocessable. However, most CANs are capable of dynamic exchange reactions through heat, and have the characteristic of being processable as the exchange reaction proceeds actively at temperatures above the topology freezing transition temperature (Tv).

[0010] Among various dynamic exchange reactions, the most widely used ester exchange reaction has a high activation energy, so the exchange reaction does not occur at relatively low temperatures without an external catalyst, but to promote it, the use of an external catalyst such as a strong base, strong acid, or inorganic material is usually essential.

[0011] However, most of the aforementioned external catalysts have poor compatibility with polymers, so they do not mix well with each other. Furthermore, as they are environmentally hazardous and corrosive materials, once mixed with polymers, separation is not easy. In particular, metal catalysts can accelerate the oxidation of polymers, which can shorten their lifespan.

[0012] Accordingly, there is an urgent need for manufacturing technology for thermosetting polymers that can be synthesized without catalysts, are physically reprocessable, and are easily soluble in various solvents, as well as for adhesives based thereon.

[0013]

[0014] The present invention aims to provide an environmentally friendly, degradable thermosetting adhesive based on dynamic crosslinking of poly(β-amino ester) and a method for manufacturing the same, characterized by synthesizing and curing the adhesive through an exchange reaction under mild conditions using an internal catalytic effect without using an external catalyst, by β-amine activating the ester exchange reaction as a solution to the problems described above.

[0015]

[0016] A preferred embodiment of the present invention for achieving the above objective provides a dynamic crosslinking-based eco-friendly degradable thermosetting adhesive characterized by comprising: a first monomer having one or more amine groups at the terminals; and a second monomer having one or more acrylate groups at the terminals; wherein the ratio of the NH amine bond of the first monomer to the C=O acrylate bond of the second monomer is 1:0.8 to 1.2.

[0017] Another preferred embodiment of the present invention provides a method for manufacturing an environmentally friendly, degradable thermosetting adhesive based on dynamic crosslinking, characterized by comprising the step of mixing a first monomer having one or more amine groups at the ends and a second monomer having one or more acrylate groups at the ends, heating and pressing the mixture, wherein the first monomer and the second monomer are mixed in a molar ratio of 1:1.5 to 2.5 to synthesize a polymer.

[0018] The above first monomer is represented by the following chemical formula 1, and it is preferable that the molecular weight (Mn) is 1800 to 2200 g / mol.

[0019] <Chemical Formula 1>

[0020]

[0021] The above second monomer comprises one or more hydroxyl group side chains and is represented by the following chemical formula 2.

[0022] <Chemical Formula 2>

[0023]

[0024] The above polymer is represented by the following chemical formula 3.

[0025] <Chemical Formula 3>

[0026]

[0027] In addition, the above polymer can be recycled and reprocessed without a catalyst.

[0028] The step of mixing the first monomer and the second monomer, heating, and pressing can be performed by heating at 110 to 130°C for 1 to 6 hours without a catalyst.

[0029] The above polymer is synthesized by an Aza-Michael addition reaction, and the network topology can be rearranged by transesterification.

[0030]

[0031] The present invention has the effect of enabling recycling because it allows for reprocessing while maintaining high adhesion between two heterogeneous interfaces when an adhesive containing dynamically crosslinked poly(β-amino ester) (PBAE CANs) is applied.

[0032] In particular, when the adhesive in PBAE CANs is exposed to water, the adhesive residue can be easily detached from the adhesive interface, allowing the adhesive to be cleanly removed from the substrate, which has the effect of enabling the recycling of the substrate material.

[0033] In addition, when the adhesive material of PBAE CANs is buried in soil, it can be decomposed using only soil moisture due to its decomposition characteristics, which has an environmentally friendly effect. Therefore, it is expected that this can be usefully utilized in the adhesive part of biodegradable plastics to build a system that can decompose completely.

[0034]

[0035] Figure 1 is a graph showing ATR-FTIR spectra according to curing time at 120°C using PEA of three different molecular weights according to a preferred embodiment of the present invention.

[0036] Figure 2 is a graph showing the GC percentage measured as a function of curing time for PBAE CANs at 120°C.

[0037] Figure 3 is a graph of DSC measurements for fully cured PBAE CANs in the temperature range from +70℃ to +140℃.

[0038] Figure 4 is a graph of DSC measurements for fully cured PBAE CANs in the temperature range from -75℃ to +75℃.

[0039] Figure 5 is a TGA (thermogravimetric analysis) measurement graph of PBAE CANs.

[0040] Figure 6 is a graph of the rheometer measurement results of PBAE CANs (temperature 120℃, deformation amplitude 0.01%~10%, axial force 5N).

[0041] Figure 7 is a graph of rheometer thermal analysis measurements of PBAE CANs (heating at 3℃ / min, frequency at 1Hz, fixed vibration strain of PBAE230 0.01%, PBAE2000 and PBAE4000 0.1%).

[0042] Figure 8 is a graph showing the fitting results of the WLF equation and the Arrhenius equation for (a~c) PBAE CANs. (d) is a graph showing a comparison of the fitting results of the Arrhenius equation for PBAE CANs synthesized using three different PEA molecular weights.

[0043] Figure 9 is a photograph showing the reprocessability of PBAE CANs over two cycles.

[0044] Figure 10 is a graph showing ATR-FTIR for CANs before and after two cycles of reprocessing for 1, 4, and 6 hours, respectively, at 120℃ and 15MPa.

[0045] Figure 11 is a DSC thermal analysis of CANs before and after two cycles of reprocessing for 1, 4, and 6 hours, respectively, at 120℃ and 15MPa.

[0046] Figure 12 is a graph showing the lap shear strength of PBAE CANs.

[0047] Figure 13 is a photograph showing the results of measuring the water contact angle of PBAE CANs.

[0048] Figure 14 is a photograph showing the damaged surface of PBAE CANs before monomer curing (a) and after curing (b).

[0049] Figure 15 is a photograph showing a PBAE2000 CANs-based adhesive supporting a weight of 55.2 kg.

[0050] Figure 16 is a graph showing the results of measuring the shear strength of PBAE2000 CANs before and after recycling.

[0051] Figure 17 is a photograph showing the hydrolysis of PBAE CANs in water at 60°C.

[0052] Figure 18 is a graph showing the gel fraction of PBAE CAN according to the time immersed in water at room temperature and 60°C.

[0053] Figure 19 is a photograph showing the hydrolysis of PBAE2000 CANs adhesive that can be easily peeled off between two substrates.

[0054] Figure 20 is a photograph showing the general characteristics of the eco-friendly biodegradable PBAE2000 CANs film.

[0055]

[0056] The present invention will be described in detail below according to preferred embodiments with reference to the attached drawings, but specific descriptions of configurations and operations that are readily known to those skilled in the art will be omitted. Furthermore, it should be noted that the present invention is not necessarily limited by the following embodiments, and that those skilled in the art can make various modifications to the invention within the scope of the technical concept of the invention without departing from it.

[0057] And numerical ranges include the values ​​defined in the above ranges. All maximum numerical limits given throughout this specification include all lower numerical limits as clearly written. All minimum numerical limits given throughout this specification include all higher numerical limits as clearly written. All numerical limits given throughout this specification include all better numerical ranges within a wider numerical range, as clearly written.

[0058] A preferred embodiment according to the present invention provides an eco-friendly, degradable thermosetting adhesive based on poly(β-amino ester) dynamic crosslinking.

[0059] The above poly(β-amino esters), PBAE, is simply synthesized by transesterification based on a catalyst-free exchange reaction system under atmospheric pressure conditions via an Aza-Michael addition reaction between an amine monomer and an acrylate monomer.

[0060] In addition, in the specification of the present invention, poly(β-amino ester) (PBAE) is synthesized by dynamic crosslinking (Covalent Adaptable Networks, CANs) as described above, so it is named 'PBAE CANs'.

[0061] In addition, the adhesive containing the above PBAE CANs is named 'PBAE CANs-based adhesive'.

[0062] The PBAE CANs-based adhesive according to the present invention may comprise a polymer synthesized such that the ratio of the NH amine bond of the first monomer to the C=O acrylate bond of the second monomer is 1:0.8 to 1.2, wherein the first monomer comprises one or more amine groups at the terminal; and the second monomer comprises one or more acrylate groups at the terminal.

[0063] The first monomer above may be a polyetheramine compound as an amine monomer compound, preferably represented by the following chemical formula 1, and the first monomer is preferably poly(propylene glycol)bis(2-aminopropyl ether (PEA), which is a polymer compound available in various molecular weights (Mn).

[0064] The molecular weight (Mn) of the first monomer PEA is preferably 1800 to 2200 g / mol, but is not necessarily limited thereto, and other compounds may be appropriately selected as needed.

[0065] <Chemical Formula 1>

[0066]

[0067] The second monomer above is a monomer comprising one or more acrylate groups at the terminals. Since the acrylate monomer applied in the present invention promotes the ester exchange reaction as the number of hydroxyl groups increases, a monomer comprising one or more hydroxyl group side chains is more preferable, and specifically, it can be represented by the following chemical formula 2.

[0068] The second monomer above is preferably glycerol 1,3-diglycerolate diacrylate (TGDA), but is not necessarily limited thereto, and other compounds may be appropriately selected as needed.

[0069] <Chemical Formula 2>

[0070]

[0071] The above polymer may be represented by the following chemical formula 3, but is not necessarily limited thereto, and other compounds may be appropriately selected as needed.

[0072] <Chemical Formula 3>

[0073]

[0074] And another preferred embodiment according to the present invention provides a method for manufacturing a PBAE CANs-based adhesive.

[0075] The method for manufacturing the above PBAE CANs-based adhesive comprises the step of mixing a first monomer having one or more amine groups at the ends; and a second monomer having one or more acrylate groups at the ends; and heating and pressing the mixture; wherein the polymer may be synthesized by mixing the first monomer and the second monomer in a molar ratio of 1:1.5 to 2.5.

[0076] The first monomer may be a polyetheramine-based compound, preferably represented by the following chemical formula 1, and the molecular weight (Mn) of the first monomer is preferably 1800 to 2200 g / mol, but is not necessarily limited thereto, and other compounds may be appropriately selected as needed.

[0077] <Chemical Formula 1>

[0078]

[0079] The above second monomer comprises one or more acrylate groups at the terminals, and is more preferably composed of one or more hydroxyl group side chains, and can be represented by the following chemical formula 2.

[0080] <Chemical Formula 2>

[0081]

[0082] The above polymer may be represented by the following chemical formula 3, but is not necessarily limited thereto, and other compounds may be appropriately selected as needed.

[0083] <Chemical Formula 3>

[0084]

[0085] Preferably, the above PBAE CANs are a polymer synthesized by mixing the first monomer and the second monomer in a molar ratio of 1:1.5 to 2.5, and the synthesized polymer is preferably synthesized such that the ratio of the NH amine bond of the first monomer to the C=O acrylate bond of the second monomer is 1:0.8 to 1.2.

[0086] If the molar ratio of the first monomer and the second monomer exceeds the range specified above, there is a risk that the unreacted material remaining after the reaction or the ratio of the bond between NH amine and C=O acrylate exceeds the range specified above, thereby degrading the desired physical properties of the PBAE CANs.

[0087] The step of mixing the first monomer and the second monomer and heating and pressing is preferably performed by heating the monomer mixture at 110 to 130°C for 1 to 6 hours without using an additional catalyst for synthesis.

[0088] If the heating process conditions are below the range specified above, the first monomer and the second monomer are not properly synthesized and cured, which may lead to a decrease in the physical properties of the synthesized PBAE CANs; if they exceed the range specified above, the physical properties of the PBAE CANs do not increase further in proportion to the increase in the heating process, which may lead to an inefficient process.

[0089] In addition, the above polymer can have its network topology rearranged by transesterification.

[0090] The present invention is characterized by the fact that PBAE CANs can be simply synthesized under atmospheric pressure conditions by an aza-Michael addition reaction between acrylate and amine, and since various types of commercial acrylate / amine monomers exist on the market, it is easy to synthesize PBAE with various physical properties.

[0091] To aid in understanding the present invention, it will be described in detail with reference to examples. However, the following examples are merely illustrative of the content of the present invention and the scope of the present invention is not limited to the following examples. The examples of the present invention are provided to more completely explain the present invention to those with average knowledge in the art.

[0092]

[0093] 1. Synthesis of Poly(β-Amino Esters (PBAE CANs)

[0094] As shown in Reaction Scheme 1 below, PBAE CANs were synthesized by mixing PEA and TGDA in a 1:2 molar ratio via an Aza-Michael addition reaction using poly(propylene glycol)bis(2-aminopropyl ether) (PEA) and glycerol 1,3-diglycerolate diacrylate (TGDA), and the specimens were specifically prepared by the method below.

[0095] PEA and TGDA were added to a THINKY mixer in a 1:2 molar ratio and mixed by stirring at 2000 rpm for 3 minutes. The mixture was then placed into a disk-shaped stainless-steel mold, and specimens were prepared by curing them at a pressure of 15 MPa using a heating press at 120°C for 1, 4, and 6 hours, respectively, for each PEA molecular weight (230, 2000, 4000 g / mol).

[0096] The PBAE CANs produced above were named PBAE230, PBAE2000, and PBAE4000, respectively, according to the molecular weight of PEA (230, 2000, 4000 g / mol).

[0097] <Reaction Equation 1>

[0098]

[0099]

[0100] 2. Characterization of Poly(β-Amino Ester (PBAE CANs))

[0101] <Experimental Example 1> Confirmation of Synthesis of Poly(β-Amino Ester (PBAE CANs)

[0102] To determine the curing time at 120°C according to molecular weight, the extent of the Aza-Michael addition reaction was confirmed by comparing ATR-FTIR spectra according to curing time using attenuated total reflection-Fourier transform infrared (ATR-FTIR).

[0103] As the Aza-Michael addition reaction proceeds while heating at 120°C, the monomer peak reaches 1630 cm⁻¹ as shown in Fig. 1. -1 C=C peak of TGDA, 1550 cm⁻¹ -1 It was confirmed that the NH bending bond peak of PEA decreased. This means that the functional groups of the monomers bond with each other to synthesize CANs.

[0104] For reference, Fig. 1 shows the ATR-FTIR spectra of PBAE CANs of different molecular weights cured at 120°C for different times, where (a) is PBAE230, (b) is PBAE2000, and (c) is PBAE4000. All ATR-FTIR spectra are at 1750 cm⁻¹. -1 It was normalized by the area of ​​the carbonyl peak appearing nearby.

[0105]

[0106] <Experimental Example 2> Analysis of Curing State

[0107] The curing state was analyzed through gel content (GC) and differential scanning calorimetry (DSC).

[0108] 1. Gel content (GC)

[0109] In the experiment measuring gel content (GC) according to curing time, the optimal curing time conditions were determined by the mass change of samples cured at different times at 120°C. Tetrahydrofuran (THF), a solvent that dissolves the monomers PEA and TGDA but does not dissolve the PBAE polymer, was used.

[0110] For PBAE CANs, CAN specimens heated to 120°C for 1, 4, and 6 hours, respectively, according to PEA molecular weight, were immersed in THF solvent for 24 hours, removed, dried in a convection oven at 60°C for 24 hours, and then calculated to measure the gel content. It was confirmed that the gel fraction converged to a constant value, and this was set as the curing completion time. The results are shown in Figure 2.

[0111] The reason the reactants do not dissolve in THF is that the cross-linking network is clearly visible after curing. The amount of unreacted monomer can be confirmed through GC, and as shown in Figure 2, a higher GC value indicates that curing occurred more effectively.

[0112] For reference, Figure 2 is a graph showing the GC percentage measured as a function of curing time for PBAE CANs at 120°C, where the green shading highlights the flatness of the fraction.

[0113] 2. Differential Scanning Calorimetry (DSC)

[0114] Using a differential scanning calorimeter (DSC), approximately 10 mg portions were placed on an aluminum pan, heated from 40°C to 150°C, cooled to -80°C, and then heated again to 150°C at a ramping rate of 5°C / min. The reported glass transition temperature (T g ) was set as the value obtained through secondary heating.

[0115] After determining whether an exothermic peak due to curing occurred in the first heating cycle with PBAE CANs fabricated after setting the curing time to 1, 4, and 6 hours respectively, and then measuring DSC after the second heating to further confirm the completion of curing of specimens that were fully cured under the curing conditions confirmed by the ATR-FTIR and GC experiments, the results showed that no exothermic peak due to curing was detected at 80 to 140°C as shown in Figure 3, and the absence of an exothermic peak due to curing is because the specimens for which DSC was measured had already completed curing.

[0116]

[0117] <Experimental Example 3> Thermal Characterization

[0118] Glass transition temperature (T g Thermal properties were analyzed through the verification of ) and thermal stability analysis.

[0119] 1. Glass transition temperature (T g Confirmation of )

[0120] Glass transition temperature (T) through DSC analysis of PBAE CANs g As a result of confirming ), as shown in Fig. 4, the intermediate glass transition temperature (T) of PBAE CANs according to molecular weight g The glass transition temperatures (T) were determined to be 3.7℃, -56.8℃, and -65.3℃, respectively; specifically, PBAE230 had a glass transition temperature (T) of 3.67℃, PBAE2000 had -56.79℃, and PBAE4000 had -65.27℃. g It was confirmed that it possesses ). This is because as the molecular weight of PEA increases, the distance between crosslinks increases and fluidity develops, resulting in a glass transition temperature (T g It was possible to confirm that ) decreased.

[0121] For reference, Fig. 4 is a graph showing the DSC thermal analysis of fully cured PBAE CANs after a second heating cycle, where the arrow indicates the intermediate glass transition temperature (T g It represents ).

[0122] 2. Thermal Stability Analysis

[0123] As a result of heating 10 mg samples of PBAE CANs from 40°C to 800°C at a heating rate of 5°C / min in a nitrogen atmosphere using a thermogravimetric analyzer (TGA), as shown in Fig. 5, T d5 (The temperature at which mass loss reaches 5% in TGA) appeared and thermal decomposition began, with PBAE230 at 248.2℃, PBAE2000 at 281.4℃, and PBAE4000 at 301.1℃ T d5 It was confirmed that the decomposition temperature gradually increases as the molecular weight of PEA increases. The stronger the intermolecular forces, the more strongly the molecules are bonded to each other, increasing resistance to heat.

[0124]

[0125] <Experimental Example 4> Thermomechanical and Mechanical Properties

[0126] The thermomechanical and mechanical properties of PBAE CANs were verified using a rheometer.

[0127] 1. Thermomechanical properties

[0128] To analyze the thermomechanical properties of PBAE CANs, the Linear Viscoelastic Region (LVR) was measured using a rheometer (MCR 702e) to determine the LVR.

[0129] The linear viscoelastic region (LVR) refers to the range where strain and stress are proportional, and in rheological measurements, experiments within the LVR range allow for the accurate evaluation of physical properties.

[0130] When all three types of samples were measured with an axial force of 5 N, as shown in Fig. 6, it was confirmed that for all three samples, the strain of 1% was within the LVR range.

[0131] For reference, Figure 6 shows the rheometer thermal analysis measurement graph of PBAE CANs. The experiment was conducted at a temperature of 120°C, a deformation amplitude of 0.01% to 10%, and an axial force of 5N. (a) is PBAE230, (b) is PBAE2000, and (c) is PBAE4000.

[0132] 2. Mechanical properties

[0133] To analyze the mechanical properties of PBAE CANs and to determine whether they were cured and the degree of crosslink density, a rheometer-temperature sweep was performed. As a result of measuring all three types of samples with an axial force of 5 N, it was confirmed through the graph, as shown in Figure 7, that the crosslink density decreased as the molecular weight of PEA increased. In other words, the appearance of a rubbery plateau confirmed that the crosslink structure was being maintained. As shown in Figure 7, PBAE CANs have a crosslink network formed by an Aza-Michael addition reaction, and it was confirmed through the temperature sweep experiment that this crosslink network was well maintained.

[0134] Furthermore, the required curing time increased as the molecular weight of the PEA used as a counterpart increased. It was confirmed that as the intermolecular distance increased, the crosslinking density decreased and the modulus of the rubbery plateau was low, resulting in relatively lower mechanical properties.

[0135] Additionally, the decrease in G' at temperatures above 120°C in all CAN specimens indicates that the crosslinks dissociate due to the aza-retro-michael addition reaction.

[0136] For reference, Figure 7 shows the rheometer thermal analysis of a PBAE CAN.

[0137]

[0138] <Experimental Example 5> Stress Relaxation Test

[0139] Relaxation time according to each temperature range of the sample, and the activation energy and topology freezing transition temperature (T) for the corresponding exchange reaction v To determine ), a stress relaxation experiment was conducted on the sample using a rheometer (HR 20 instrument) under conditions of an axial force of 5N and a strain of 1% to measure the relaxation time according to each temperature range, and this was fitted to the Williams-Landel-Ferry (WLF) equation in (1) below and the Arrhenius equation in (2) below to determine the activation energy for the exchange reaction and the topological freezing transition temperature (T v ) was obtained.

[0140] (1)

[0141] In the above, τ is the stress relaxation time, τ ref is T ref Stress relaxation time at, T is the measurement temperature, Tref is the reference temperature, and constants C1 and C2 are fitting variables.

[0142] (2)

[0143] In the above, τ is the stress relaxation time, A is a variable related to the frequency coefficient (s), and Ea ε is the activation energy (J / mol), T is the measured temperature (K), and R is the gas constant (8.314×10⁻⁶). -3 kJ / K-mol)

[0144] In PBAE CANs, the molecular topology can be rearranged through two dynamic exchange reactions, the dynamic Aza-Michael reaction and the ester exchange reaction, as shown in Reaction Scheme 2 below.

[0145] <Reaction Equation 2>

[0146]

[0147] In addition, β-amine esters in PBAE can undergo an ester exchange reaction at relatively mild low temperatures without a catalyst through internal catalysis and neighboring group participation effects, as shown in Reaction Scheme 3 below.

[0148] <Reaction Equation 3>

[0149]

[0150] As shown in reaction schemes 2 and 3 above, the rheological properties of the exchange reaction were observed at temperatures above the temperature at which the dynamic exchange reaction occurs.

[0151] The ester exchange reaction occurs at temperatures above approximately 80°C, and at temperatures above that, the activation energy for the exchange reaction and the topological freezing transition temperature (T v ) can be obtained.

[0152] For reference, (ac) of FIG. 8 is a graph showing the fitting results of the WLF equation of (1) and the Arrhenius equation of (2) for PBAE CANs, and the relaxation time was extracted by fitting the Maxwell equation of (3) below, where stress relaxation is stretched at various temperatures. (d) shows the activation energy of PBAE CANs.

[0153] (3)

[0154] In the above, σ is stress, σ0 is initial stress, t is time, τ is stress relaxation time, and β is the amplification index.

[0155] In the low-temperature region, the WLF equation of (1) above is followed, in which segmental motion strongly controls the relaxation time. In the high-temperature region, the Arrhenius equation is followed, in which the exchange reaction controls the relaxation time more strongly than segmental motion. When these equations are fitted, the temperature of the intersection point is the topological freezing transition temperature (T v It was defined as ), and T by molecular weight v It is as summarized in [Table 1] below.

[0156] It was confirmed that relaxation time and activation energy appeared similar without any trend, regardless of molecular weight control.

[0157] Classification E a [kJ / mol]T g [℃]T v [℃]PBAE230104.93.6794PBAE200095.5-56.7998PBAE4000119.9-56.79101.55

[0158] As shown above, relaxation time and glass transition temperature (T) according to PEA molecular weight g ), activation energy (E a The reason ) comes out similarly is that all three types of polymers have glass transition temperatures (T g A relatively high temperature (minimum T) where ) is lower than room temperature and exchange reactions occur actively gSince the diffusion times scale is already very low at +90℃, it is presumed that the results are all controlled solely by kinetics without the influence of diffusion. As they all possess similar chemical structures and functional groups, it is estimated that the three types of PBAE CANs have similar kinetic parameters when diffusion parameters are not considered. Based on the above results, the topological freezing transition temperature (T v It is estimated that processing by exchange reaction is possible or similar at 100℃ or higher.

[0159]

[0160] <Experiment Example 6> Recycling & Reprocessing properties

[0161] PBAE CANs are the topology freezing transition temperature (T v Material recycling is possible through heat and pressure without a catalyst at temperatures above ) This is because, although it has a cross-linked network, unlike thermosetting polymers, ester exchange reactions and dynamic Aza-Michael exchange reactions occur between functional groups, giving it malleability.

[0162] Topology freezing transition temperature (T v As shown in Fig. 9, a result of perfect reprocessing was obtained using molds of various shapes at a temperature of 120°C and a pressure of 5 MPa.

[0163] As a result of analyzing the specimens before and after reprocessing using ATR-FTIR and DSC during a total of two reprocessing cycles, the ATR-FTIR results and the glass transition temperature (T gIt was confirmed that there was almost no difference. It was found that even through repeated heat treatment at 120°C, it was not chemically or thermally deformed, as shown in FIGS. 10 and FIGS. 11. This is presumed to be the result of increased stability against oxidation, etc., due to the absence of an external catalyst.

[0164] For reference, Figure 9 is a photograph showing the reprocessability of PBAE CANs over two cycles, and the heat pressing between each cycle was performed for PBAE230, PBAE2000, and PBAE4000 at 120°C and 15 MPa for 1, 4, and 6 hours, respectively.

[0165] Figure 10 is a graph showing ATR-FTIR for CANs before and after two cycles of reprocessing treatment for 1, 4, and 6 hours at 120℃ and 15MPa, respectively, where (a) is PBAE230, (b) is PBAE2000, and (c) is PBAE4000.

[0166] Figure 11 is a DSC thermal analysis of CANs before and after two reprocessing treatments at 120℃ and 15MPa for 1, 4, and 6 hours, respectively, where (a) is PBAE230, (b) is PBAE2000, and (c) is PBAE4000.

[0167]

[0168] <Experimental Example 7> Adhesive properties

[0169] As a result of conducting a lap shear test to analyze the adhesive strength of PBAE CANs according to molecular weight, as shown in Figure 12, it was confirmed that PBAE2000 exhibited the highest tensile strength, followed by PBAE230 and PBAE4000 in decreasing order of tensile strength.

[0170] In order to identify the reasons for the coating properties and the causes of adhesion / cohesion failure in the adhesion results, photographs of the results of the deionized water (DI. water) contact angle and fracture tests of PBAE CANs according to molecular weight are shown in Figures 13 and 14.

[0171] For reference, the fracture test was performed using a universal testing machine (QM100TM) with a tensile test (speed of 1.27 mm / min), a SUS304 substrate of 25.4 mm × 101.6 mm, a bonding area of ​​25.4 mm × 12.7 mm, a thickness of 0.1 mm, and a loading cell of 100 kgf, measured until the point of fracture.

[0172] In addition, for the contact angle test, the PBAE film was cured flat on a glass substrate using a heating plate, and the contact angle was measured using a contact angle tester (PHEONIX-300) with a 20 µl drop of deionized water (DIwater). After droplet formation, a stabilization time of approximately 10 seconds was given, and the contact angle measurement was performed.

[0173] It was confirmed that the cured PBAE230 had a contact angle of 17.93°, PBAE2000 had 45.17°, and PBAE4000 had 81.61°. This indicates that when using PEA with a low molecular weight, the aliphatic chain length becomes relatively shorter and the hydroxyl group density is high. This increases surface tension and raises the cohesive force between monomers, resulting in poor coating performance on substrates such as SUS. On the other hand, as PEA with a higher molecular weight is used, the surface tension of the monomer mixture decreases, and consequently, the cohesive force of the monomer mixture decreases, leading to improved coating performance.

[0174] In the case of a mixture of PBAE230 monomers, which is relatively the most hydrophilic, it is expected that coating will be difficult due to the strong cohesion between the monomers, as shown in the pre-coating photo above. This is because the surface tension is relatively high. It was observed that the sample clumped together in the pre-curing photo. Due to the poor coating performance and the high cohesion between the PBAE CANs as described above, adhesion failure occurs, and it appears to have relatively low adhesion strength.

[0175] PBAE4000, which has the longest aliphatic chain, exhibited excellent coating properties due to its low surface tension and experienced cohesion failure. However, it possessed low mechanical properties due to its low crosslinking density, and it is presumed that this resulted in reduced lap shear strength.

[0176] PBAE2000 not only prevents cohesion failure but also has relatively high adhesion due to appropriate hydrophilicity and cohesion, and can be used as a material with high adhesion and CAN performance.

[0177] An experiment was conducted to lift 55.2 kg using an adhesive applied to an actual substrate as shown in Fig. 15, and through this, it was confirmed that the adhesive can be applied not only on an experimental scale but also in actual field conditions, and that a heavy weight can be lifted with a small amount of adhesive.

[0178] Samples from adhesive wrap shear strength tests using PBAE2000 CANs were recovered and subjected to reuse experiments by applying heat. Due to the characteristics of the CANs, reprocessing is possible. As shown in Fig. 16, the recycled specimens were reattached to the damaged surfaces at 120°C and 0.5 MPa for 1 hour for measurement, and through this experiment, it was confirmed that material properties can be realized through re-adhesion.

[0179] When using PEA with an average molecular weight of 2000 g / mol, the best lap shear strength is observed, which is presumed to be due to the excellent coating properties resulting from the relatively low surface energy and the relatively high degree of crosslinking.

[0180]

[0181] <Experimental Example 8> Chemical Recyclability in Heated Water

[0182] Chemical decomposition of PBAE CANs was possible simply by placing them in heated water instead of using toxic organic solvents, and the interfaces could also be cleanly removed.

[0183] The following reaction scheme 4 is intended to explain the mechanism of hydrolysis of PBAE CANs in heated water by an ester exchange reaction, and the hydrolysis of PBAE is a substitution reaction in which the hydroxyl group of water attacks the carbonyl group of the ester, and as shown in reaction scheme 4 below, β-amine promotes ester activation in the substitution reaction.

[0184] As such, the Aza-Michael addition reaction has the advantage of being a click reaction that can yield a high yield under mild conditions, and the PBAE CANs synthesized in this way can undergo an exchange reaction under mild conditions without an additional catalyst due to the effects of internal catalyst and neighbor group participating.

[0185] <Reaction Equation 4>

[0186]

[0187] For reference, Figure 17 is a photograph showing the hydrolysis of PBAE CANs. When PBAE230, PBAE2000, and PBAE4000 were immersed in water at 60°C in samples of the same size (1 cm × 1 cm), after 24 hours, PBAE230 and PBAE2000 were both dissolved, but PBAE4000 was not dissolved.

[0188] As shown in the contact angle experiment results of Fig. 13 above, as the molecular weight of PEA increases, water resistance increases along with hydrophobicity, and the decomposition rate gradually slows down. As shown in Fig. 18, it can be confirmed that the decomposition rate can be further accelerated by increasing the temperature even for CANs of the same molecular weight, which is the result of the ester exchange reaction with the solvent being accelerated as the temperature increases. For reference, Fig. 18 is a graph showing the gel fraction of PBAE CANs as a function of the time immersed in water at 60°C (dotted line) (the solid line represents the result obtained with water at room temperature).

[0189] For reference, Figure 19 is a photograph showing the hydrolysis of PBAE2000 CANs adhesive, which can be easily peeled between two substrates. By utilizing this hydrolyzable property, an experiment was conducted to separate the two substrates by bonding them with PBAE2000 CANs adhesive and then dissolving the adhesive in water. As a result, chemical decomposition through hydrolysis was achieved as shown in Figure 19.

[0190] PBAE CANs exhibit hydrolytic properties in eco-friendly solvents such as water. It is confirmed that as the molecular weight of PEA increases, hydrophobicity increases, leading to a significant decrease in the hydrolysis rate. This suggests the possibility of effectively controlling the polymer degradation rate.

[0191] In an experiment utilizing these properties in which PBAE CANs were applied as an adhesive between two heterogeneous interfaces, it was shown that the adhesive could be easily detached from the interface without leaving adhesive residue when exposed to water, while maintaining high adhesion. This is expected to enable clean removal of the adhesive in the future and facilitate the recycling of the substrate.

[0192]

[0193] <Experimental Example 9> Bio-degradable property

[0194] It was confirmed through Experiment 8 above that environmentally friendly chemical decomposition via water is possible. To apply this, a decomposition experiment was conducted using a culture medium in which the entire specimen was not in contact with water but was appropriately distributed. As shown in Fig. 20, a PBAE2000 CANs film with a thickness of 100 μm and dimensions of 10 cm × 10 cm was decomposed within 72 hours through the culture medium. This indicates that the film was decomposed through esterification using water in the culture medium that possessed sufficient hydrosyl groups.

[0195] For reference, Figure 20 is a photograph showing the general characteristics of an eco-friendly biodegradable PBAE2000 CANs film, which can be applied to the adhesive part of biodegradable plastic to create a system in which the entire adhesive can be degraded.

[0196] As confirmed through the above examples, as the molecular weight of PEA increases, the crosslinking density decreases and fluidity increases, and the glass transition temperature (T g It was confirmed that as the molecular weight increases, the molecular force becomes stronger, increasing resistance to heat and resulting in a higher decomposition temperature.

[0197] And, possessing β-amine functional groups, it enables transesterification reaction activity without the use of a catalyst, and when rheological properties were measured, the topological freezing transition temperature (T v ) and E aThere was no trend of increase or decrease. The reason is that at high temperatures, where the Arrhenius equation significantly controls relaxation time, the diffusion-controlled mechanism is not dominant and the kinetic-controlled mechanism is dominant; therefore, the exchange reaction is highly active, and the temperature-dependent stress relaxation time and E a PBAE CANs 230, 2000, and 4000 all showed similar values.

[0198] Topology freezing transition temperature (T) in 3 types of PBAE CANs v ) appears at 90–100℃, and it was confirmed that CANs exchange reaction behavior occurs actively above this temperature. In addition, the topological freezing transition temperature (T) identified above v It was confirmed that reprocessing, which is a characteristic of CANs, is possible under pressure. Even after reprocessing, it was observed through ATR-FTIR or DSC that the reprocessing was completed without any change in physical properties.

[0199] In addition, when a lap shear test was conducted to measure adhesive performance, PBAE2000 exhibited the highest adhesive strength and was the most suitable for use as it possessed excellent tensile strength with surface tension and cohesiveness of the CANs material suitable for application.

[0200] However, PBAE230 had the highest surface tension and cohesiveness among them, making it difficult to apply, and strong intermolecular forces resulted in adhesion failure. Additionally, PBAE4000 had the lowest surface tension and good applicability, but its low crosslinking density led to poor mechanical properties, making it unsuitable for use as an adhesive.

[0201] After using the adhesive, the substrate was placed in heated water to recover it without damage or adhesive residue, thereby confirming the eco-friendly chemical decomposition of the adhesive. As a result, it was confirmed that β-amine promotes the activation of the ester in the above reaction through a substitution reaction in which the hydroxyl group of water attacks the carbonyl group of PBAE CANs.

[0202] In addition, contact angle experiments confirmed that PBAE230 is hydrophilic and PBAE4000 is hydrophobic, and through this, it was determined that resistance to water can be controlled by controlling the crosslinking density. Due to these characteristics, PBAE2000, which is recommended as an adhesive for its intermediate molecular weight, made it easy to recover the substrate after use.

[0203] The thermosetting adhesive according to the present invention can be decomposed using water from the contact area and can be decomposed by being embedded in culture soil; therefore, this characteristic is expected to be useful in constructing a system capable of overall decomposition by utilizing it in the adhesive part of biodegradable plastics.

[0204] Although an environmentally friendly, degradable thermosetting adhesive based on dynamic crosslinking of Poly(β-amino esters) and a method for manufacturing the same have been described according to a preferred embodiment of the present invention as described above, this is merely an example and those skilled in the art will understand that various changes and modifications are possible within the scope of the technical spirit of the present invention.

Claims

1. A first monomer comprising one or more amine groups at the terminal; and A second monomer comprising one or more acrylate groups at the terminal; wherein A dynamic crosslinking-based eco-friendly degradable thermosetting adhesive characterized by comprising a polymer synthesized such that the ratio of the NH amine bond of the first monomer to the C=O acrylate bond of the second monomer is 1:0.8 to 1.

2.

2. In Paragraph 1, The above first monomer is, An eco-friendly, biodegradable thermosetting adhesive based on dynamic crosslinking, characterized by being represented by the following chemical formula 1. <Chemical Formula 1> 3. In Paragraph 2, The above first monomer is, An eco-friendly, biodegradable thermosetting adhesive based on dynamic crosslinking, characterized by a molecular weight (Mn) of 1800 to 2200 g / mol.

4. In Paragraph 1, The above second monomer is, A dynamic crosslinking-based eco-friendly biodegradable thermosetting adhesive characterized by containing one or more hydroxyl group side chains.

5. In Paragraph 4, The above second monomer is, An eco-friendly, biodegradable thermosetting adhesive based on dynamic crosslinking, characterized by being represented by the following chemical formula 2. <Chemical Formula 2> 6. In Paragraph 1, The above polymer is, A dynamic crosslinking-based eco-friendly degradable thermosetting adhesive characterized by being represented by the following chemical formula 3. <Chemical Formula 3> 7. In Paragraph 6, The above polymer is, An eco-friendly, biodegradable thermosetting adhesive based on dynamic crosslinking, characterized by being recyclable and reprocessable without a catalyst.

8. In Paragraph 6, The above polymer is, A dynamic crosslinking-based eco-friendly degradable thermosetting adhesive characterized by rearranging the network topology through transesterification.

9. A first monomer comprising one or more amine groups at the terminal; and A second monomer comprising one or more acrylate groups at the terminal end; mixed, heated, and pressed; comprising the step of A method for manufacturing an environmentally friendly, degradable thermosetting adhesive based on dynamic crosslinking, characterized by including a polymer synthesized by mixing the first monomer and the second monomer in a molar ratio of 1:1.5 to 2.

5.

10. In Paragraph 9, The above first monomer is, A method for manufacturing an environmentally friendly, biodegradable thermosetting adhesive based on dynamic crosslinking, characterized by being represented by the following chemical formula 1. <Chemical Formula 1> 11. In Paragraph 9, The above first monomer is, A method for manufacturing an eco-friendly, degradable thermosetting adhesive based on dynamic crosslinking, characterized by a molecular weight (Mn) of 1800 to 2200 g / mol.

12. In Paragraph 9, The above second monomer is, A method for manufacturing an eco-friendly, degradable thermosetting adhesive based on dynamic crosslinking, characterized by including one or more hydroxyl group side chains.

13. In Paragraph 12, The above second monomer is, A method for manufacturing an environmentally friendly, biodegradable thermosetting adhesive based on dynamic crosslinking, characterized by being represented by the following chemical formula 2. <Chemical Formula 2> 14. In Paragraph 9, The above polymer is, A method for manufacturing an environmentally friendly, degradable thermosetting adhesive based on dynamic crosslinking, characterized by being represented by the following chemical formula 3. <Chemical Formula 3> 15. In Paragraph 14, The above polymer is, A method for manufacturing an environmentally friendly, degradable thermosetting adhesive based on dynamic crosslinking, characterized in that the ratio of the NH amine bond of the first monomer to the C=O acrylate bond of the second monomer is 1:0.8 to 1.

2.

16. In Paragraph 9, The step of mixing the first monomer and the second monomer, heating, and pressing is A method for manufacturing an environmentally friendly, degradable thermosetting adhesive based on dynamic crosslinking, characterized by heating at 110 to 130°C for 1 to 6 hours without a catalyst.

17. In Paragraph 9, The above polymer is, A method for manufacturing an eco-friendly, degradable thermosetting adhesive based on dynamic crosslinking, characterized by being synthesized by an Aza-Michael addition reaction.

18. In Paragraph 9, The above polymer is, A method for manufacturing an eco-friendly, degradable thermosetting adhesive based on dynamic crosslinking, characterized by rearranging the network topology through transesterification.

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