Supramolecular polyurethane hot melt adhesive as well as preparation method and application thereof

Abstract

The invention discloses a supramolecular polyurethane hot melt adhesive as well as a preparation method and application thereof. The structural formula of the supramolecular polyurethane hot melt adhesive is # imgabs0 #, wherein R1 is derived from a cross-linking agent, R2 is derived from a first monomer, R3 is derived from a second monomer, R4 is derived from a third monomer, and M is an end-capping reagent; g is a linking group formed among the cross-linking agent, the first monomer, the second monomer, the third monomer and the end-capping reagent; the cross-linking agent is selected from a polyamino and / or polyhydroxy cross-linking agent, the first monomer is selected from a diisocyanate compound, the second monomer is selected from a diamine and / or diol oligomer, the third monomer is selected from a diketoxime compound, and the end-capping reagent has a pyrimidine ring. According to the invention, the processing temperature of the hot melt adhesive is obviously reduced, so that the hot melt adhesive has good processing fluidity and interface wettability at a lower temperature, has excellent room-temperature mechanical properties, ensures the mechanical strength of the adhesive, and can also show excellent interface bonding strength in a low-temperature environment.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer and supramolecular materials, and particularly relates to a supramolecular polyurethane hot melt adhesive, a preparation method thereof, and an application thereof. Background Art

[0002] Hot melt adhesives are a class of organic polymer materials that can strongly bond to the surface of adherends by heating. According to their chemical structures, they can be divided into two categories: thermoplastic hot melt adhesives and thermosetting hot melt adhesives. Among them, thermosetting hot melt adhesives have the characteristics of good processing fluidity and high bonding strength. Thermosetting hot melt adhesives represented by epoxy resins have been widely used in engineering, but their weakness is that they are brittle and cannot be recycled, which causes a certain degree of waste of resources and environmental pollution and does not conform to the development concepts of "carbon neutrality" and "carbon peak". On the other hand, although thermoplastic hot melt adhesives represented by linear polyolefins can be processed and used repeatedly, their non-polar molecular structure has poor adhesion to the surface of the adhered object, resulting in low bonding strength.

[0003] Thermoplastic polyurethane is a class of polymers copolymerized from soft segments and hard segments. The strong polarity of the hard segments can strongly bond to the surface of the adherend, thereby improving the bonding strength. It is a star material for current thermoplastic hot melt adhesives (Adv. Funct. Mater. 2022, 2204263). However, the prerequisite for its bonding is that the hard phase needs to undergo physical dissociation at a high temperature (for example, 200 °C) to endow it with fluidity and good interfacial wettability. Since the soft segments are prone to chemical degradation when they are at a high temperature for a long time, it will damage their mechanical properties. Therefore, how to achieve the flow of the adhesive and interfacial wetting at a lower temperature, and at the same time maintain excellent mechanical properties in a room temperature environment and a low temperature environment (≤25 °C) is one of the bottlenecks in the development of current thermoplastic polyurethane adhesives. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a supramolecular polyurethane hot melt adhesive, a preparation method thereof, and an application thereof.

[0005] To achieve the foregoing invention purpose, the technical solutions adopted by the present invention include:

[0006] In the first aspect, the present invention provides a supramolecular polyurethane hot melt adhesive, and the structural formula of the supramolecular polyurethane hot melt adhesive is represented as:

[0007]

[0008] Among them, R1 is derived from a cross-linking agent, R2 is derived from a first monomer, R3 is derived from a second monomer, R4 is derived from a third monomer, and M represents a capping agent; G is a linking group formed between the cross-linking agent, the first monomer, the second monomer, the third monomer, and the capping agent;

[0009] The crosslinking agent is selected from polyamino and / or polyhydroxy crosslinking agents, the first monomer is selected from diisocyanate compounds, the second monomer is selected from diamine and / or diol oligomers, the third monomer is selected from dioxime compounds, and the capping agent has a pyrimidine ring.

[0010] In a second aspect, the present invention also provides a method for preparing the above-mentioned supramolecular polyurethane hot melt adhesive, which includes:

[0011] Carrying out a first chemical reaction between the first monomer and the second monomer to obtain a first system, and there is a remaining amount of the first monomer in the first reaction system;

[0012] Adding the third monomer to the first reaction system to carry out a second chemical reaction to obtain a second system;

[0013] Adding a capping agent to the second system to carry out a capping reaction to obtain a third system, and the third system contains a plurality of branched chain units formed by polymerization of the first monomer, the second monomer, the third monomer and the capping agent;

[0014] Adding a crosslinking agent to the third system to cause the plurality of branched chain units to crosslink with the crosslinking agent to form the molecular structure of the supramolecular polyurethane hot melt adhesive.

[0015] In a third aspect, the present invention also provides the application of the above-mentioned supramolecular polyurethane hot melt adhesive in the field of hot melt bonding, and the temperature of the hot melt bonding is 60-140°C.

[0016] Based on the above technical solutions, compared with the prior art, the beneficial effects of the present invention at least include:

[0017] The hyperbranched polyurethane hot melt adhesive and its preparation method provided by the present invention construct a supramolecular hot melt adhesive with excellent strength and toughness through the synergy of multiple hydrogen bond interactions between the urethane or urea groups generated by monomer connection and the capped pyrimidine groups. On this basis, by introducing oxime groups at the corresponding positions of the branched chains, the processing temperature is significantly reduced through the reversible decomposition reaction of oxime-urethane, so it has good processing fluidity and interfacial wettability at a lower temperature, and has excellent room temperature mechanical properties, ensuring the mechanical strength of the adhesive, and can also exhibit excellent interfacial bonding strength at low temperature environments.

[0018] The above description is only an overview of the technical solutions of the present invention. In order to enable those skilled in the art to understand the technical means of the present application more clearly and implement it according to the content of the specification, the following is a detailed description with reference to the preferred embodiments of the present invention and the accompanying drawings. Description of the Drawings

[0019] Figure 1The infrared spectrum of the hyperbranched polyurethane hot melt adhesive prepared in a typical embodiment of the present invention;

[0020] Figure 2 The bonding strength test chart of the hyperbranched polyurethane hot melt adhesive prepared in a typical embodiment of the present invention at room temperature;

[0021] Figure 3 The stress-strain curve of the hyperbranched polyurethane hot melt adhesive prepared in another typical embodiment of the present invention;

[0022] Figure 4 The bonding strength test chart of the hyperbranched polyurethane hot melt adhesive prepared in yet another typical embodiment of the present invention when used for bonding aluminum and polycarbonate at a low temperature of -70°C. Detailed implementation manners

[0023] In view of the deficiencies in the prior art, the inventors of this case have, through long-term research and a large number of practices, been able to propose the technical solution of the present invention. The following will further explain and illustrate this technical solution, its implementation process, principles, etc.

[0024] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0025] Moreover, relative terms such as "first" and "second" are only used to distinguish one component or method step with the same name from another, and do not necessarily require or imply any such actual relationship or order between these components or method steps.

[0026] An embodiment of the present invention provides a supramolecular polyurethane hot melt adhesive, and the structural formula of the supramolecular polyurethane hot melt adhesive is represented as:

[0027]

[0028] Among them, R1 is derived from a crosslinking agent, R2 is derived from a first monomer, R3 is derived from a second monomer, R4 is derived from a third monomer, and M represents a capping agent; G is a linking group formed between the crosslinking agent, the first monomer, the second monomer, the third monomer, and the capping agent; the crosslinking agent is selected from polyamino and / or polyhydroxy crosslinking agents, the first monomer is selected from diisocyanate compounds, the second monomer is selected from diamine and / or diol oligomers, the third monomer is selected from dioxime compounds, and the capping agent has a pyrimidine ring.

[0029] As a typical example of the above technical solution, an embodiment of the present invention provides a supramolecular hot melt adhesive as shown in formula (I),

[0030]

[0031] Among them, R1 is the group of the polyfunctional crosslinking agent except hydrogen; G is a ureido group or a urethane group; R2 is the group of the diisocyanate except the isocyanate group; R3 is the group of the diamine oligomer or the diol oligomer except the amino / hydroxyl group; R4 is the group of the dioxime compound except the hydroxyl group; represents several other groups (other branches) connected to R1, and its structure is consistent with the group connected to the right side of R1 in formula (I) (it can be exactly the same, or it can have the same structural characteristics but the specific chain lengths of different branches may be different).

[0032] Based on the above technical solutions, in view of the problems such as most of the existing supramolecular hot melts being linear structures, the present application provides a hyperbranched supramolecular hot melt and its preparation method, which constructs a supramolecular hot melt with excellent strength and toughness through the synergistic effect of multiple hydrogen bond interactions between urethane or ureido groups and pyrimidine groups. On this basis, by introducing an appropriate amount of oxime groups at selected positions on the branches, the processing temperature is significantly reduced by using its reversible decomposition reaction, and bonding can be carried out when the temperature is raised to 60-140 °C.

[0033] Based on the above solutions and principles, on the one hand, the present invention reduces the processing temperature of the adhesive, realizes good processing fluidity and interfacial wettability at a lower temperature, and on the other hand, endows excellent room temperature mechanical properties by introducing a large number of polar groups, ensuring the mechanical strength of the adhesive; thirdly, due to the good movement ability of the soft segment molecules, it shows excellent interfacial bonding strength at low temperature environments.

[0034] Meanwhile, during the synthesis of the supramolecular hot melt, the specific properties of the adhesive material can be further adjusted by changing the chemical composition of the supramolecular arms, the content of the monofunctional capping agent, and the functionality of the crosslinking agent, thereby effectively controlling the material properties to meet different application requirements.

[0035] Regarding the specific structural numerical characteristics, in some embodiments, the value range of n is 1-4.

[0036] In some embodiments, only one of x and y is not 0, and the value range of x or y is 0-5.

[0037] In some embodiments, the number average molecular weight of the second monomer is 1000-2000.

[0038] In some embodiments, the functionality of the crosslinking agent is 3-4.

[0039] Regarding the specific molecular structures of the monomers, end-capping agents, and cross-linking agents, in some embodiments, the first monomer includes any one or a combination of two of isophorone diisocyanate and dicyclohexylmethane 4,4'-diisocyanate;

[0040] In some embodiments, the second monomer includes any one or a combination of two of polytetrahydrofuran diol and polyetheramine;

[0041] In some embodiments, the third monomer includes any one or a combination of two or more of dimethylglyoxime, 2,4-pentanedione dioxime, and 1,2-cyclohexanedione dioxime;

[0042] In some embodiments, the cross-linking agent includes any one or a combination of two or more of tris(2-aminoethyl)amine, melamine, glycerol, and 2-hydroxy-N,N-bis(2-hydroxyethyl)-N-methylethanaminium methyl sulfate;

[0043] In some embodiments, the end-capping agent includes any one or a combination of two or more of 2-amino-4-hydroxy-6-methylpyrimidine, 3-amino-4-hydroxypyrimidine, 2-amino-5,6-dimethyl-4-hydroxypyrimidine, and (9ci)-6-amino-2-hydroxy-4( 1 H)-pyrimidinone.

[0044] Correspondingly, the second aspect of the embodiments of the present invention further provides a preparation method of the supramolecular polyurethane hot melt adhesive provided in any of the above embodiments, which includes the following steps:

[0045] Carry out a first chemical reaction between the first monomer and the second monomer to obtain a first system, and there is a remaining amount of the first monomer in the first reaction system;

[0046] Add the third monomer to the first reaction system to carry out a second chemical reaction to obtain a second system;

[0047] Add an end-capping agent to the second system to carry out an end-capping reaction to obtain a third system, and the third system contains a plurality of branched chain units polymerized from the first monomer, the second monomer, the third monomer, and the end-capping agent;

[0048] Add a cross-linking agent to the third system to enable a cross-linking reaction between the plurality of branched chain units and the cross-linking agent to form the molecular structure of the supramolecular polyurethane hot melt adhesive.

[0049] In the above preparation method, in order to successfully obtain the supramolecular polyurethane hot melt adhesive desired by the present invention, the reaction sequence and the reaction feed ratio are crucial, and the reaction must be carried out according to the defined reaction sequence and excess ratio. This is because the second monomer R3 is a long-chain molecule with good solubility and will not aggregate even after reacting with the first monomer R2. On the contrary, if the third monomer R4 reacts with the first monomer R2 first, the resulting product is still a small molecule, and there is a strong hydrogen bond interaction between molecules, which is prone to aggregation and even precipitation from the solution. Once aggregation occurs, it will affect the subsequent reaction degree and even cause crosslinking, resulting in the failure of the reaction. Therefore, in order to achieve the purpose of the present invention, adopting an appropriate reaction sequence and excess relationship is a key factor.

[0050] Regarding the specific material ratio relationship, in some embodiments, when feeding materials, the molar ratio of the first monomer to the second monomer is (1.5 - 8):1;

[0051] In some embodiments, the molar ratio of the third monomer to the second monomer is (0.5 - 6):1;

[0052] In some embodiments, the molar ratio of the capping agent to the second monomer is (0.1 - 1):1.

[0053] Regarding other reagents other than the monomers and reagents directly related to the molecular structure, in some embodiments, the first system further includes a solvent for dissolving the first monomer and the second monomer and a catalyst for catalyzing the first chemical reaction, the second chemical reaction, the capping reaction, and the crosslinking reaction.

[0054] Specifically, in some embodiments, when feeding materials, the dosage of the catalyst is less than 1% of the total mass of the first monomer and the second monomer;

[0055] In some embodiments, the solvent is 2 - 10 times the total mass of the first monomer and the second monomer.

[0056] In some embodiments, the preparation method further includes: after the crosslinking reaction, removing the solvent in the system to obtain the supramolecular polyurethane hot melt adhesive.

[0057] Of course, even if those skilled in the art do not remove the above solvent by volatilization or heating, but provide a glue solution dissolved with the hyperbranched molecule having the above structural features as a commodity, and the user removes the solvent before bonding to obtain a colloid for hot melt bonding, or directly coats it on the surface of an object, waits for it to dry and volatilize to spontaneously form a colloid, and then heats and melts it to bond with other objects, all fall within the feasible implementation scope of the present invention and are also protected by the claims of the present invention. It can be understood that no matter which application method is adopted, any method involving the molecular structural features and bonding characteristics provided by the present invention utilizes the technical concept contributed by the present invention.

[0058] Regarding the specific reaction conditions, in some embodiments, the temperature of the first chemical reaction is 60 - 100 °C, and the time is 30 - 180 min;

[0059] In some embodiments, the temperature of the second chemical reaction is 60 - 100 °C, and the time is 30 - 120 min;

[0060] In some embodiments, the temperature of the end-capping reaction is 60 - 100 °C;

[0061] In some embodiments, the temperature of the cross-linking reaction is 60 - 100 °C.

[0062] As some typical application examples of the above technical solutions, the preparation method of the above supramolecular polyurethane hot melt adhesive includes the following specific steps:

[0063] A) Add diamine oligomer or diol oligomer, an appropriate amount of solvent, diisocyanate, and catalyst into a reaction vessel, then start stirring evenly, set the reaction temperature to 70 - 100 °C, and the reaction duration is 30 - 300 min;

[0064] B) Add an appropriate amount of dioxime compound into the system of step A), and continue the reaction for 10 - 120 min;

[0065] C) Add an appropriate amount of 2-amino-4-hydroxy-6-methylpyrimidine (UPy) as a single-end capping agent into the system of step B);

[0066] D) Slowly add an appropriate amount of polyfunctional cross-linking agent containing hydroxyl or amino groups into the system of step C), and the reaction duration is 15 - 180 min.

[0067] E) After the solvent is completely volatilized, the supramolecular polyurethane hot melt adhesive is obtained.

[0068] Specifically, the glycol oligomer is selected from polytetrahydrofuran glycol (PTMEG) with a number average molecular weight Mn of 1000 - 2000 g / mol, and the diamine oligomer is selected from polyetheramine with a number average molecular weight Mn of 2000 g / mol; the isocyanate is selected from one of isophorone diisocyanate (IPDI) and dicyclohexylmethane 4,4'-diisocyanate (HMDI); the dioxime compound is selected from dimethylglyoxime (DEO); the molar ratio of the glycol compound or diamine compound to the isocyanate is 1:(1.5 - 8). The solvent is selected from one or more of N,N'-dimethylformamide, N,N'-dimethylacetamide, and tetrahydrofuran. In step A), the temperature range of the reaction device is 60°C - 100°C, and the reaction time is 30 - 180 min.

[0069] In step A), the catalyst is selected from dibutyltin dilaurate, and the amount of the catalyst does not exceed 1 wt% of the reaction raw materials in step A). In step B), the molar ratio of the dimethylglyoxime to the glycol oligomer or diamine oligomer is (0.5 - 6):1, and the reaction time is 30 - 120 min. In step C), the molar ratio of 2-amino-4-hydroxy-6-methylpyrimidine to the glycol oligomer or diamine oligomer is (0.1 - 1):1. In step D), the multifunctional crosslinking agent is selected from one or more of tris(2-aminoethyl)amine, melamine, glycerol, and 2-hydroxy-N,N-bis(2-hydroxyethyl)-N-methylethanaminium methyl sulfate, and the molar ratio of the multifunctional crosslinking agent to the glycol oligomer and / or diamine oligomer is 1:(3 - 20).

[0070] The experimental results show that the tensile strength of the supramolecular hot melt adhesive material of the present invention can reach 21 MPa, the elongation at break can reach more than 450%, the bonding strength of bonding an aluminum plate and polycarbonate together can be greater than 3.5 MPa, and various set shapes can be obtained by hot processing at a temperature of 60 - 140°C, having good shape plasticity and mechanical properties.

[0071] Furthermore, the third aspect of the embodiments of the present invention also provides the application of the above supramolecular polyurethane hot melt adhesive in the field of hot melt bonding, and the temperature of the hot melt bonding is 60 - 140°C. In particular, the application of the above supramolecular hot melt adhesive in room temperature and low temperature bonding.

[0072] The technical solutions of the present invention are further described in detail below through several embodiments in combination with the drawings. However, the selected embodiments are only used to illustrate the present invention and do not limit the scope of the present invention.

[0073] Example 1

[0074] This example exemplifies a preparation method of a supramolecular hot melt adhesive, including the following steps:

[0075] S1. Add polytetrahydrofuran diol (structural formula 1-I) to the reaction vessel. After building an inert gas atmosphere, add an appropriate amount of the solvent N,N'-dimethylformamide, add dicyclohexylmethane 4,4'-diisocyanate (structural formula 1-II) and a small amount of the catalyst dibutyltin dilaurate, start stirring, heat up to 80 °C and turn on the condensation reflux device, and react for two hours.

[0076]

[0077] S2. Add an appropriate amount of dimethylglyoxime (structural formula 1-III) to the system described in S1, and continue to react for two hours.

[0078]

[0079] S3. Add an appropriate amount of 2-amino-4-hydroxy-6-methylpyrimidine (structural formula 1-IV). When the solution becomes colorless and transparent, the reaction is complete.

[0080]

[0081] S4. Slowly add an appropriate amount of tris(2-aminoethyl)amine (structural formula 1-V) to the system described in S3, continuously react and observe for 15 min. If there are no phenomena such as excessive viscosity and gelation, the reaction is successful.

[0082]

[0083] S5. After thoroughly removing the bubbles from the reacted solution, pour it into a mold, volatilize to form a film, and obtain the supramolecular hot melt adhesive after completely removing the solvent.

[0084] Among them, the molar ratio of dicyclohexylmethane 4,4'-diisocyanate to polytetrahydrofuran diol in S1 is 7:2.

[0085] Among them, the mass fraction of the catalyst dibutyltin dilaurate in the system in S1 is 0.5 wt%.

[0086] Among them, the molar ratio of dimethylglyoxime used in S2 to polytetrahydrofuran diol in S1 is 2:1.

[0087] Among them, the molar ratio of 2-amino-4-hydroxy-6-methylpyrimidine used in S3 to polytetrahydrofuran diol in S1 is 1:2.

[0088] Among them, the molar ratio of tris(2-aminoethyl)amine used in S4 to polytetrahydrofuran diol in S1 is 1:6.

[0089] The molecular formula of the supramolecular hot melt adhesive obtained in this example is shown as follows (for easy reading, the following formula is horizontally interrupted and arranged vertically. The complete molecular formula is the splicing of the upper left, lower left, upper right, and lower right of the following formula, the same below):

[0090]

[0091] Figure 1 is the infrared spectrum of the hot melt adhesive prepared in Example 1 of this embodiment; Figure 2 is the test chart of the bonding strength between aluminum and polycarbonate at room temperature using the hot melt adhesive in Example 1 of this embodiment. The melting temperature during bonding is 100 °C. It can be seen from the infrared spectrum that under the influence of extensive hydrogen bonds, the stretching vibration peak of the C=O group shows a red shift phenomenon. From the bonding strength of 4.5 MP at room temperature, it can be seen that the bonding performance of the hot melt adhesive material provided in this embodiment is excellent.

[0092] Example 2

[0093] This example demonstrates a preparation method of a supramolecular hot melt adhesive, including the following steps:

[0094] S1. Add polytetrahydrofuran diol (structural formula 2-I) to a reaction vessel. After building an inert gas atmosphere, add an appropriate amount of solvent N,N'-dimethylformamide, add dicyclohexylmethane 4,4'-diisocyanate (structural formula 2-II) and a small amount of catalyst dibutyltin dilaurate, start stirring, heat up to 80 °C and turn on the condenser reflux device, and react for two hours.

[0095]

[0096] S2. Add an appropriate amount of dimethylglyoxime (structural formula 2-III) to the system described in S1, and continue to react for two hours.

[0097]

[0098] S3. Add an appropriate amount of 2-amino-4-hydroxy-6-methylpyrimidine (structural formula 2-IV), and wait until the solution becomes colorless and transparent, indicating that the reaction is complete.

[0099]

[0100] S4. Slowly add an appropriate amount of tris(2-aminoethyl)amine (structural formula 2-V) to the system described in S3, continuously react and observe for 15 minutes. If there are no phenomena such as excessive viscosity or gelation, the reaction is successful.

[0101]

[0102] S5. After thoroughly removing the bubbles from the reacted solution, pour it into a mold, volatilize to form a film, and remove the solvent completely to obtain a supramolecular hot melt adhesive.

[0103] Among them, the molar ratio of dicyclohexylmethane 4,4'-diisocyanate to polytetrahydrofuran diol in S1 is 4:1.

[0104] Among them, the mass fraction of the catalyst dibutyltin dilaurate in the system in S1 is 0.5 wt%.

[0105] Among them, the molar ratio of dimethylglyoxime used in S2 to polytetrahydrofuran diol in S1 is 2:1.

[0106] Among them, the molar ratio of 2-amino-4-hydroxy-6-methylpyrimidine used in S3 to polytetrahydrofuran diol in S1 is 1:1.

[0107] Among them, the molar ratio of tris(2-aminoethyl)amine used in S4 to polytetrahydrofuran diol in S1 is 1:3.

[0108] The molecular formula of the supramolecular hot melt adhesive obtained in this example is shown as the following formula:

[0109]

[0110] The bonding melting temperature of this hot melt adhesive is 127 °C. Figure 3 This is the stress-strain curve graph of the hot melt adhesive prepared in Example 2; this curve graph shows that this hot melt adhesive has both strong cohesive strength and toughness.

[0111] Example 3

[0112] This example exemplifies a preparation method of a supramolecular hot melt adhesive, including the following steps:

[0113] S1. Add polytetrahydrofuran diol (structural formula 3-I) to a reaction vessel. After building an inert gas atmosphere, add an appropriate amount of solvent N,N'-dimethylformamide, add dicyclohexylmethane 4,4'-diisocyanate (structural formula 3-II) and a small amount of catalyst dibutyltin dilaurate, start stirring, heat up to 80 °C and turn on the condensing reflux device, and react for 120 min.

[0114]

[0115] S2. Add an appropriate amount of dimethylglyoxime (structural formula 3-III) to the system described in S1, and continue to react for 90 min.

[0116]

[0117] S3. Add an appropriate amount of 2-amino-4-hydroxy-6-methylpyrimidine (structural formula 3-IV), and wait until the solution becomes colorless and transparent, which means the reaction is complete.

[0118]

[0119] S4. Slowly add an appropriate amount of tris(2-aminoethyl)amine (structural formula 3-V) to the system described in S3, continuously react and observe for 15 min. If there are no phenomena such as excessive viscosity or gelation, the reaction is successful.

[0120]

[0121] S5. After thoroughly removing the bubbles from the reacted solution, pour it into a mold and volatilize to form a film. After completely removing the solvent, a supramolecular hot melt adhesive is obtained.

[0122] Among them, the molar ratio of dicyclohexylmethane 4,4'-diisocyanate to polytetrahydrofuran diol in S1 is 11:6.

[0123] Among them, the number-average molecular weight M of the polytetrahydrofuran diol used in S1 n = 2000.

[0124] Among them, the mass fraction of the catalyst dibutyltin dilaurate in the system in S1 is 0.5 wt%.

[0125] Among them, the molar ratio of dimethylglyoxime used in S2 to the polytetrahydrofuran diol in S1 is 2:3.

[0126] Among them, the molar ratio of 2-amino-4-hydroxy-6-methylpyrimidine used in S3 to the polytetrahydrofuran diol in S1 is 1:6.

[0127] Among them, the molar ratio of tris(2-aminoethyl)amine used in S4 to the polytetrahydrofuran diol in S1 is 1:18.

[0128] The molecular formula of the supramolecular hot melt adhesive obtained in this example is shown as follows:

[0129]

[0130] Figure 4 This is the test chart of the bonding strength of Example 3 for the bonding of aluminum to polycarbonate at a low temperature of -70°C. The melting temperature during bonding is 54°C, and then the test is carried out in an environment of -70°C; it can be seen from the figure that it has very excellent low-temperature bonding performance.

[0131] Example 4

[0132] This example exemplifies a preparation method of a supramolecular hot melt adhesive, including the following steps:

[0133] S1. Add polytetrahydrofuran diol (structural formula 4-I) into the reaction vessel. After building an inert gas atmosphere, add an appropriate amount of the solvent N,N'-dimethylformamide, then add dicyclohexylmethane 4,4'-diisocyanate (structural formula 4-II) and a small amount of catalyst dibutyltin dilaurate. Start stirring, heat up to 80 °C and turn on the condenser reflux device, and react for two hours.

[0134]

[0135] S2. Add an appropriate amount of dimethylglyoxime (structural formula 4-III) into the system described in S1, and continue to react for two hours.

[0136]

[0137] S3. Add an appropriate amount of 2-amino-4-hydroxy-6-methylpyrimidine (structural formula 4-IV). When the solution becomes colorless and transparent, the reaction is complete.

[0138]

[0139] S4. Slowly add an appropriate amount of tris(2-aminoethyl)amine (structural formula 4-V) into the system described in S3, continuously react and observe for 15 min. If there are no phenomena such as excessive viscosity and gelation, the reaction is successful.

[0140]

[0141] S5. After thoroughly removing the bubbles from the reacted solution, pour it into a mold and let it volatilize to form a film. After completely removing the solvent, a supramolecular hot melt adhesive is obtained.

[0142] Among them, the molar ratio of dicyclohexylmethane 4,4'-diisocyanate to polytetrahydrofuran diol in S1 is 2:1.

[0143] Among them, the number-average molecular weight M n = 1000.

[0144] Among them, the mass fraction of the catalyst dibutyltin dilaurate in the system in S1 is 1 wt%.

[0145] Among them, the molar ratio of dimethylglyoxime used in S2 to polytetrahydrofuran diol in S1 is 1:2.

[0146] Among them, the molar ratio of 2-amino-4-hydroxy-6-methylpyrimidine used in S3 to polytetrahydrofuran diol in S1 is 1:2.

[0147] Among them, the molar ratio of tris(2-aminoethyl)amine used in S4 to polytetrahydrofuran diol in S1 is 1:6.

[0148] The molecular formula of the supramolecular hot melt adhesive obtained in this example is shown as follows:

[0149]

[0150] The bonding melting temperature of this hot melt adhesive is 100 °C, and it also has very excellent bonding performance and low-temperature performance.

[0151] Example 5

[0152] This example demonstrates a preparation method of a supramolecular hot melt adhesive, including the following steps:

[0153] S1. Add polyetheramine D-2000 (structural formula 5-I) into the reaction vessel. After building an inert gas atmosphere, add an appropriate amount of solvent N,N'-dimethylformamide, add dicyclohexylmethane 4,4'-diisocyanate (structural formula 5-II) and a small amount of catalyst dibutyltin dilaurate, start stirring, heat up to 80 °C and turn on the condenser reflux device, and react for two hours.

[0154]

[0155] S2. Add an appropriate amount of dimethylglyoxime (structural formula 5-III) to the system described in S1, and continue to react for two hours.

[0156]

[0157] S3. Add an appropriate amount of 2-amino-4-hydroxy-6-methylpyrimidine (structural formula 5-IV), and wait until the solution becomes colorless and transparent, indicating that the reaction is complete.

[0158]

[0159] S4. Slowly add an appropriate amount of tris(2-aminoethyl)amine (structural formula 5-V) to the system described in S3, continuously react and observe for 15 min. If there are no phenomena such as excessive viscosity and gelation, the reaction is successful.

[0160]

[0161] S5. Pour the reacted solution into a mold after thoroughly removing the bubbles, volatilize to form a film, and obtain the supramolecular hot melt adhesive after removing the solvent completely.

[0162] Among them, the molar ratio of dicyclohexylmethane 4,4'-diisocyanate to polyetheramine D-2000 in S1 is 2:1.

[0163] Among them, the number-average molecular weight M of polyetheramine D-2000 used in S1 n = 2000.

[0164] Among them, the mass fraction of the catalyst dibutyltin dilaurate in S1 in the system is 0.5 wt%.

[0165] Among them, the molar ratio of dimethylglyoxime used in S2 to polyetheramine D-2000 in S1 is 1:2.

[0166] Among them, the molar ratio of 2-amino-4-hydroxy-6-methylpyrimidine used in S3 to polyetheramine D-2000 in S1 is 1:2.

[0167] Among them, the molar ratio of tris(2-aminoethyl)amine used in S4 to polyetheramine D-2000 in S1 is 1:6.

[0168] The molecular formula of the supramolecular hot melt adhesive obtained in this example is shown as follows:

[0169]

[0170] The bonding melting temperature of this hot melt adhesive is 120 °C, and it also has very excellent bonding performance and low-temperature performance.

[0171] Comparative Example 1

[0172] This comparative example exemplifies a preparation method of a supramolecular hot melt adhesive, which is substantially the same as that in Example 2, and the main difference lies in that the third monomer R4 is different and it does not contain a ketoxime group.

[0173] This comparative example specifically includes the following steps:

[0174] S1. Add polytetrahydrofuran diol (structural formula 6-I) to the reaction vessel. After building an inert gas atmosphere, add an appropriate amount of solvent N,N'-dimethylformamide, add dicyclohexylmethane 4,4'-diisocyanate (structural formula 6-II) and a small amount of catalyst dibutyltin dilaurate, start stirring, heat up to 80 °C and turn on the condensation reflux device, and react for 120 min.

[0175]

[0176] S2. Add an appropriate amount of 1,4-butanediol (structural formula 6-III) to the system described in S1, and continue to react for 90 min.

[0177]

[0178] S3. Add an appropriate amount of 2-amino-4-hydroxy-6-methylpyrimidine (structural formula 6-IV), and wait until the solution becomes colorless and transparent, which means the reaction is complete.

[0179]

[0180] S4. Slowly add an appropriate amount of tris(2-aminoethyl)amine (structural formula 6-V) to the system described in S3, continuously react and observe for 15 min. If there are no phenomena such as excessive viscosity or gelation, the reaction is successful.

[0181]

[0182] S5. After thoroughly removing the bubbles from the reacted solution, pour it into a mold and volatilize to form a film. After removing the solvent completely, a supramolecular hot melt adhesive is obtained.

[0183] Among them, the molar ratio of dicyclohexylmethane 4,4'-diisocyanate to polytetrahydrofuran diol in S1 is 4:1.

[0184] Among them, the number-average molecular weight M n = 2000.

[0185] Among them, the mass fraction of the catalyst dibutyltin dilaurate in the system in S1 is 0.5 wt%.

[0186] Among them, the molar ratio of 1,4-butanediol used in S2 to polytetrahydrofuran diol in S1 is 2:1.

[0187] Among them, the molar ratio of 2-amino-4-hydroxy-6-methylpyrimidine used in S3 to polytetrahydrofuran diol in S1 is 1:1.

[0188] Among them, the molar ratio of tris(2-aminoethyl)amine used in S4 to polytetrahydrofuran diol in S1 is 1:3.

[0189] Compared with Example 2, the bonding melting temperature of this hot melt adhesive is 160 °C, and the bonding strength at room temperature is 2.5 MPa, only 62% of the room temperature bonding strength of Comparative Example 2.

[0190] This shows that the dioxime group introduced at a certain position in the molecular chain can, on the basis of the synergistic effect of multiple hydrogen bond interactions between the urethane or urea group and the pyrimidine group, further significantly reduce the processing temperature through its own molecular structure characteristics.

[0191] In addition, according to the description of the present invention, the inventors of the present invention also adjusted the chemical reaction conditions, and hyperbranched molecules with the above structural characteristics can be synthesized within an appropriate temperature and time range, and they all have similar processing temperatures and bonding characteristics after separation, which will not be elaborated here.

[0192] Based on the above embodiments and comparative examples, it can be clearly seen that the hyperbranched polyurethane hot melt adhesive and its preparation method provided by the embodiments of the present invention construct a supramolecular hot melt adhesive with excellent strength and toughness through the synergy of the multiple hydrogen bond interactions between the urethane or urea groups generated by monomer connection and the capped pyrimidine groups. On this basis, by introducing oxime groups at the corresponding positions of the branched chains, the processing temperature is significantly reduced through the reversible decomposition reaction of the oxime groups. Therefore, it has good processing fluidity and interfacial wettability at a lower temperature, and has excellent room temperature mechanical properties, ensuring the mechanical strength of the adhesive, and can also exhibit excellent interfacial bonding strength in a low temperature environment.

[0193] It should be understood that the above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and its purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A supramolecular polyurethane hot melt adhesive, characterized in that, The structural formula of the supramolecular polyurethane hot melt adhesive is expressed as: Among them, R1 is derived from the crosslinking agent, R2 is derived from the first monomer, R3 is derived from the second monomer, R4 is derived from the third monomer, and M represents the end-capping agent; G is the linking group formed between the crosslinking agent, the first monomer, the second monomer, the third monomer, and the end-capping agent; The crosslinking agent is selected from polyamino and / or polyhydroxy crosslinking agents, the first monomer is selected from diisocyanate compounds, the second monomer is selected from diamine and / or diol oligomers, the third monomer is selected from dioxime compounds, and the end-capping agent has a pyrimidine ring.

2. The supramolecular polyurethane hot melt adhesive according to claim 1, wherein The value range of n is 1-4; And / or, only one of x and y is not 0, and the value range of x or y is 0-5; And / or, the number average molecular weight of the second monomer is 1000-2000; And / or, the functionality of the crosslinking agent is 3-4.

3. The supramolecular polyurethane hot melt adhesive according to claim 1, wherein The first monomer includes any one or a combination of two of isophorone diisocyanate and dicyclohexylmethane 4,4'-diisocyanate; And / or, the second monomer includes any one or a combination of two of polytetrahydrofuran diol and polyetheramine; And / or, the third monomer includes any one or a combination of two or more of butanedione dioxime, 2,4-pentanedione dioxime, and 1,2-cyclohexanedione dioxime; And / or, the crosslinking agent includes any one or a combination of two or more of tris(2-aminoethyl)amine, melamine, glycerol, and 2-hydroxy-N,N-bis(2-hydroxyethyl)-N-methylethanaminium methyl sulfate; And / or, the end-capping agent includes any one or a combination of two or more of 2-amino-4-hydroxy-6-methylpyrimidine, 3-amino-4-hydroxy pyrimidine, 2-amino-5,6-dimethyl-4-hydroxy pyrimidine, and (9ci)-6-amino-2-hydroxy-4(1H)-pyrimidinone.

4. The preparation method of the supramolecular polyurethane hot melt adhesive according to any one of claims 1-3, characterized in that, It includes: Carrying out a first chemical reaction between the first monomer and the second monomer to obtain a first system, and there is a remaining amount of the first monomer in the first reaction system; Adding the third monomer to the first reaction system to carry out a second chemical reaction to obtain a second system; Adding the end-capping agent to the second system to carry out an end-capping reaction to obtain a third system, and the third system contains a plurality of branched chain units polymerized from the first monomer, the second monomer, the third monomer, and the end-capping agent; Adding the crosslinking agent to the third system to enable the plurality of branched chain units to undergo a crosslinking reaction with the crosslinking agent to form the molecular structure of the supramolecular polyurethane hot melt adhesive.

5. The preparation method according to claim 4, characterized in that, During feeding, the molar ratio of the first monomer to the second monomer is (1.5-8):1; And / or, the molar ratio of the third monomer to the second monomer is (0.5-6):1; And / or, the molar ratio of the end-capping agent to the second monomer is (0.1-1):

1.

6. The preparation method according to claim 4, characterized in that, The first system further includes a solvent for dissolving the first monomer and the second monomer and a catalyst for catalyzing the first chemical reaction, the second chemical reaction, the end-capping reaction, and the crosslinking reaction.

7. The preparation method according to claim 6, characterized in that, During feeding, the dosage of the catalyst is less than 1% of the total mass of the first monomer and the second monomer; And / or, the solvent is 2-10 times the total mass of the first monomer and the second monomer.

8. The preparation method according to claim 6, wherein It further includes: After the cross-linking reaction, the solvent in the system is removed to obtain the supramolecular polyurethane hot melt adhesive.

9. The preparation method according to claim 4, characterized in that, The temperature of the first chemical reaction is 60-100 °C, and the time is 30-180 min; And / or, the temperature of the second chemical reaction is 60-100 °C, and the time is 30-120 min; And / or, the temperature of the capping reaction is 60-100 °C; And / or, the temperature of the cross-linking reaction is 60-100 °C.

10. Use of the supramolecular polyurethane hot melt adhesive according to any one of claims 1-3 in the field of hot melt bonding, characterized in that, The temperature of the hot melt bonding is 130-140 °C.

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