Formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid and preparation method thereof

Abstract

The present disclosure provides a formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazolium heterocyclic ionic liquids and a preparation method thereof. The formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazolium heterocyclic ionic liquids comprises a polyurethane structure containing a hindered urea bond, substituted imidazole cations and fluorinated sulfonyl imide anions. The formaldehyde-free polyurethane adhesive, through the use of a polyurethane structure containing a hindered urea bond, substituted imidazole cations and fluorinated sulfonyl imide anions, not only reduces the number of free isocyanate groups, but also improves the bonding strength of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazolium heterocyclic ionic liquids, and also improves the fluidity of the polyurethane molecular chain in the polyurethane structure containing a hindered urea bond to reduce the difficulty of processing, and also realizes rapid self-repair of leather goods materials, and also reduces the amount of organic solvents used to avoid excessive residual amounts that affect human health.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and in particular to a formaldehyde-free polyurethane adhesive for highly conductive leather goods containing an imidazole heterocyclic ionic liquid and a preparation method thereof. Background Art

[0002] Formaldehyde-free polyurethane adhesive is a common adhesive for leather goods. Since formaldehyde-free polyurethane adhesive is rich in highly chemically active isocyanate groups, it can achieve a firm bond with leather goods. However, the poor conductivity of formaldehyde-free polyurethane adhesive makes it impossible to apply it to some highly conductive leather goods, which is not conducive to the development of multifunctional leather goods, such as smart device leather goods, electronic equipment and accessories leather goods, etc.

[0003] To this end, Chinese patent document No. CN 114478491A discloses a high-adhesion ionic liquid adhesive, which uses the unique conductivity, electrochemical stability, and non-flammability of halogen ion ionic liquids to give the adhesive special functions to meet the application of multifunctional leather products.

[0004] However, since the halogen ions in the ionic liquid of halogen ions have relatively weak electrical conductivity and the ionic radius of halogen ions is large, the halogen ions have limited effect on improving the conductivity of the above-mentioned high-adhesion ionic liquid adhesive and cannot be applied to high-conductivity multifunctional leather products.

[0005] In addition, since the formaldehyde-free polyurethane adhesive is rich in highly chemically active isocyanate groups, the number of free isocyanate groups is high, resulting in incomplete reaction of the isocyanate groups. The unreacted isocyanate groups will cause the relative molecular mass of the prepolymer to decrease, resulting in a significant decrease in the viscosity of the adhesive. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids, which reduces the number of free isocyanate groups, improves the bonding strength of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids, improves the fluidity of the polyurethane molecular chain in the polyurethane structure containing hindered urea bonds, thereby reducing the difficulty of processing, and realizes rapid self-repair of leather goods materials, and reduces the amount of organic solvent used to avoid excessive residual amounts that affect human health. A formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids and a preparation method thereof.

[0007] The purpose of this disclosure is achieved through the following technical solutions: The invention discloses a formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazolium heterocyclic ionic liquid. The formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazolium heterocyclic ionic liquid comprises a polyurethane structure containing a hindered urea bond, substituted imidazole cations and fluorine-containing sulfonyl imide anions.

[0008] In one embodiment, the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid has the following structural formula: A method for preparing a formaldehyde-free polyurethane adhesive for highly conductive leather goods containing an imidazole heterocyclic ionic liquid comprises the following steps: obtaining a polyurethane prepolymer having terminal isocyanate groups; The isocyanate-terminated polyurethane prepolymer is subjected to a chain extension reaction using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid to obtain a highly conductive formaldehyde-free polyurethane adhesive for leather goods containing imidazole heterocyclic ionic liquid; wherein the chain extension reaction conditions are as follows: the reaction temperature is 70°C to 85°C, the reaction time is 2h to 4h, and the stirring speed is 200 r / min to 400r / min.

[0009] In one of the embodiments, the step of obtaining a polyurethane prepolymer having terminal isocyanate groups includes the following specific steps: reacting a polymer polyol, isophorone diisocyanate and a catalyst to synthesize a polyurethane prepolymer having terminal isocyanate groups; wherein the reaction conditions are: initially reacting at 55°C to 60°C for 20min to 30min, then heating to 65°C to 70°C, continuing the reaction for 20min to 30min, then heating to 75°C to 80°C, and ending the reaction after 0.5h to 1.5h.

[0010] In one embodiment, the polymeric polyol comprises at least one of polytetrahydrofuran, polybutylene adipate, polycarbonate diol and polypropylene glycol; and / or, The catalyst comprises at least one of dibutyltin dilaurate, bismuth acetate, bismuth acetylacetonate, dimethylcyclohexylamine and N,N-dimethylbenzylamine; and / or, The polymeric polyol and the isophorone diisocyanate are used in a molar ratio of 1:3; and / or, The molecular weight of the polymeric polyol is 1000-1200.

[0011] In one embodiment, the piperazine heterocyclic dispersion includes at least one of (±)piperazine-2-carboxylic acid dispersion, 1-carboxymethylpiperazine dispersion, N-carboxyethylpiperazine dispersion, N,N'-dicarboxyethylpiperazine dispersion and piperazine-1,4-dicarboxylic acid dispersion.

[0012] In one embodiment, the (±)piperazine-2-carboxylic acid dispersion is a mixture of (±)piperazine-2-carboxylic acid and an amide organic solvent.

[0013] In one embodiment, the molar ratio of (±)piperazine-2-carboxylic acid in the (±)piperazine-2-carboxylic acid dispersion to -NCO in the isocyanate-terminated polyurethane prepolymer is (1-5):10.

[0014] In one embodiment, the imidazolium heterocycle-containing ionic liquid includes at least one of 1-butyl-3-methylimidazolium di(trifluoromethylsulfonyl)imide ionic liquid, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid, 1-propyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid and 1-pentyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid.

[0015] In one of the embodiments, the mass ratio of the 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide ionic liquid to the isocyanate-terminated polyurethane prepolymer is (13-120):100.

[0016] Compared with the prior art, the present invention has at least the following advantages: 1) Since the hindered urea bond in the polyurethane structure containing hindered urea bonds can be decomposed into amines and isocyanates under specific conditions (neutral conditions and the presence of simple nucleophiles), the self-healing effect on the leather material can be achieved; and the dynamic properties of the hindered urea bonds in the polyurethane structure containing hindered urea bonds can form an interpenetrating network structure similar to "hand in hand" inside the leather material, thereby enhancing the internal structure of the leather material, bringing more hydrogen bonds, and thus improving the bonding strength of the formaldehyde-free polyurethane adhesive for highly conductive leather containing imidazolium heterocyclic ionic liquids; and since the nitrogen atom on the imidazole ring in the substituted imidazole cation carries a positive charge, while the fluorinated sulfonyl imide anion carries a negative charge, it is beneficial to the migration of charges in the polyurethane structure; thereby improving the conductivity of the formaldehyde-free polyurethane adhesive for highly conductive leather containing imidazolium heterocyclic ionic liquids; compared with traditional For ionic liquids of halogen ions, the substituents introduced into the substituted imidazole cations can effectively adjust their charge distribution and ionic radius. In addition, the fluorinated sulfonyl imide anions have strong electronegativity and small size, which further optimizes the ion conductivity. In addition, the interaction between the substituted imidazole cations and the fluorinated sulfonyl imide anions is weak, which makes the ion conduction efficiency in the polyurethane structure higher, thereby ensuring that the prepared formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids has high conductivity, that is, the ion exchange channels are constructed by imitating the cell membrane material exchange to improve the ion migration performance, thereby achieving the combination of excellent bonding performance and excellent electrical properties of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids, and improving its antibacterial properties to better adapt to the application of highly conductive multifunctional leather products.

[0017] 2) Since substituted imidazole cations and fluorinated sulfonyl imide anions can form ion pairs, and these ion pairs can affect the distribution and activity of isocyanate groups through electrostatic interactions or steric hindrance effects, the number of free isocyanate groups is reduced to ensure that the isocyanate groups can react completely, thereby improving the bonding strength of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids, effectively avoiding the problem of low adhesion caused by the high number of free isocyanate groups in traditional formaldehyde polyurethane adhesives due to the high chemical activity of isocyanate groups.

[0018] 3) Since the ionic liquid formed by the substituted imidazole cation and the fluorinated sulfonyl imide anion has a low viscosity, when it is introduced into the polyurethane structure containing hindered urea bonds, the fluidity of the polyurethane molecular chain in the polyurethane structure containing hindered urea bonds can be changed, effectively avoiding processing problems such as sticking to the board that are prone to occur during the processing.

[0019] 4) Since the fluorinated sulfonyl imide anions have a certain nucleophilicity, mainly because the fluorinated group has a strong electron-withdrawing effect, thereby reducing the negative charge density of the fluorinated sulfonyl imide anions, and the fluorinated alkyl group also has a certain degree of steric hindrance effect, so that the fluorinated sulfonyl imide anions exhibit weak coordination characteristics, and are easy to approach and attack the electrophilic part of the hindered urea bond, thereby accelerating the self-repair rate of the leather material, so as to achieve rapid self-repair of the leather material.

[0020] 5) Due to the introduction of substituted imidazole cations and fluorinated sulfonyl imide anions, the use of organic solvents is reduced, effectively avoiding the excessive residual amount of organic solvents in traditional leather goods that affects human health. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 This is a flow chart of a formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid according to one embodiment of the present invention; Figure 2 This is a schematic diagram of the reaction of 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide ionic liquid, isocyanate-terminated polyurethane prepolymer and piperazine-containing heterocyclic dispersion according to one embodiment of the present invention; Figure 3 This is a self-repairing effect diagram of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid according to Example 10 of the present invention; Figure 4 This is a physical picture of the conductivity test of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid in Example 10 of the present invention. DETAILED DESCRIPTION

[0023] In order to facilitate the understanding of the present disclosure, the present disclosure will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present disclosure are given in the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present disclosure more thoroughly and comprehensively understood.

[0024] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present disclosure belongs. The terms used herein in the specification of the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0026] The present invention discloses a formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazolium heterocyclic ionic liquids. The formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazolium heterocyclic ionic liquids comprises a polyurethane structure containing a hindered urea bond, a substituted imidazole cation, and a fluorine-containing sulfonyl imide anion.

[0027] The above-mentioned formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid, due to the combined use of hindered urea bond polyurethane structure, substituted imidazole cations and fluorinated sulfonyl imide anions, not only reduces the number of free isocyanate groups, but also improves the bonding strength of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid, and also improves the fluidity of the polyurethane molecular chain in the hindered urea bond polyurethane structure to reduce the processing difficulty, and also realizes rapid self-repair of leather materials, and also reduces the use of organic solvents to avoid excessive residual amounts that affect human health.

[0028] See also Figure 1 In order to better understand the technical solutions and beneficial effects of the present invention, the present invention is further described in detail below in conjunction with specific embodiments. An embodiment of the present invention provides a formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazolium heterocyclic ionic liquids. The formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazolium heterocyclic ionic liquids comprises a polyurethane structure containing a hindered urea bond, a substituted imidazole cation, and a fluorine-containing sulfonyl imide anion.

[0029] It can be understood that the hindered urea bond in the polyurethane structure containing hindered urea bonds can be decomposed into amines and isocyanates under specific conditions (neutral conditions and the presence of simple nucleophiles), thereby achieving a self-healing effect on leather materials; and the dynamic properties of the hindered urea bonds in the polyurethane structure containing hindered urea bonds can form an interpenetrating network structure similar to "hand in hand" inside the leather material, thereby enhancing the internal structure of the leather material, bringing more hydrogen bonds, and thereby improving the bonding strength of the formaldehyde-free polyurethane adhesive for highly conductive leather containing imidazolium heterocyclic ionic liquids; and because the nitrogen atom on the imidazole ring in the substituted imidazole cation carries a positive charge, while the fluorinated sulfonyl imide anion carries a negative charge, it is beneficial to the migration of charges in the polyurethane structure; thereby improving the conductivity of the formaldehyde-free polyurethane adhesive for highly conductive leather containing imidazolium heterocyclic ionic liquids; relative to traditional For ionic liquids containing halogen ions, the substituents introduced into the substituted imidazole cations can effectively adjust their charge distribution and ionic radius. In addition, the fluorinated sulfonyl imide anions have strong electronegativity and small size, which further optimizes the ion conductivity. In addition, the interaction between the substituted imidazole cations and the fluorinated sulfonyl imide anions is weak, which makes the ion conduction efficiency in the polyurethane structure higher, thereby ensuring that the prepared formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids has high conductivity, that is, the ion exchange channels are constructed by imitating the cell membrane material exchange to improve the ion migration performance, thereby achieving the combination of excellent bonding performance and excellent electrical properties of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids, and improving its antibacterial properties, so as to better adapt to the application of highly conductive multifunctional leather products.

[0030] It can also be understood that, since substituted imidazole cations and fluorinated sulfonyl imide anions can form ion pairs, and these ion pairs can affect the distribution and activity of isocyanate groups through electrostatic interactions or steric hindrance effects, the number of free isocyanate groups is reduced to ensure that the isocyanate groups can react completely, thereby improving the bonding strength of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids, effectively avoiding the problem of low adhesion caused by the high number of free isocyanate groups in traditional formaldehyde polyurethane adhesives due to the high chemical activity of isocyanate groups.

[0031] It can also be understood that since the ionic liquid formed by the substituted imidazole cation and the fluorinated sulfonyl imide anion has a lower viscosity, when it is introduced into a polyurethane structure containing a hindered urea bond, the fluidity of the polyurethane molecular chain in the polyurethane structure containing a hindered urea bond can be changed, effectively avoiding processing problems such as sticking to the board that are easy to occur during the processing process.

[0032] It can also be understood that since the fluorinated sulfonyl imide anions have a certain nucleophilicity, it is mainly because the fluorinated group has a strong electron-withdrawing effect, thereby reducing the negative charge density of the fluorinated sulfonyl imide anions, and the fluorinated alkyl group also has a certain degree of steric hindrance effect, so that the fluorinated sulfonyl imide anions exhibit weak coordination characteristics, which are easy to approach and attack the electrophilic part of the hindered urea bond, thereby accelerating the self-repair rate of the leather material, so as to achieve rapid self-repair of the leather material.

[0033] It can also be understood that the introduction of substituted imidazole cations and fluorinated sulfonyl imide anions reduces the amount of organic solvents used, effectively avoiding the excessive amount of organic solvents used in traditional leather goods, which can lead to excessive residual amounts and affect human health.

[0034] In one embodiment, the imidazolium heterocycle-containing ionic liquid includes at least one of 1-butyl-3-methylimidazolium di(trifluoromethylsulfonyl)imide ionic liquid, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid, 1-propyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid and 1-pentyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid, so as to ensure that the added imidazolium heterocycle-containing ionic liquid includes both substituted imidazole cations and fluorinated sulfonyl imide anions.

[0035] In a preferred embodiment, the imidazolium heterocyclic ionic liquid is the 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid.

[0036] It can be understood that since the 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid has better conductivity, solubility, stability and antibacterial properties than the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid, the 1-propyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid and the 1-pentyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid, it is beneficial to prepare a highly conductive formaldehyde-free polyurethane adhesive for leather goods containing imidazole heterocyclic ionic liquids with excellent bonding properties, excellent electrical properties and antibacterial properties, which is particularly suitable for the application of highly conductive multifunctional leather products.

[0037] In a preferred embodiment, the aldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid is mainly prepared by chain extension reaction of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid, polyurethane prepolymer with terminal isocyanate group and piperazine heterocyclic dispersion liquid. Specifically, the aldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid has the following structural formula: For details, please refer to Figure 2Schematic diagram of the reaction between 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide ionic liquid, isocyanate-terminated polyurethane prepolymer and piperazine-containing heterocyclic dispersion.

[0038] The present disclosure also provides a method for preparing a formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid, comprising the following steps: obtaining a polyurethane prepolymer having terminal isocyanate groups; carrying out a chain extension reaction on the polyurethane prepolymer having terminal isocyanate groups using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid to obtain the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid; wherein the chain extension reaction conditions are as follows: a reaction temperature of 70° C. to 85° C., a reaction time of 2 h to 4 h, and a stirring speed of 200 r / min to 400 r / min.

[0039] The method for preparing a formaldehyde-free polyurethane adhesive for highly conductive leather goods containing an imidazole heterocyclic ionic liquid in one embodiment comprises some or all of the following steps: S101, obtaining a polyurethane prepolymer having an isocyanate group terminal for later use.

[0040] In one embodiment, the step of obtaining a polyurethane prepolymer having terminal isocyanate groups includes the following specific steps: reacting a polymerized polyol, isophorone diisocyanate and a catalyst to synthesize a polyurethane prepolymer having terminal isocyanate groups; wherein the reaction conditions are: initially reacting at 55°C to 60°C for 20min to 30min, then heating to 65°C to 70°C, continuing to react for 20min to 30min, then heating to 75°C to 80°C, and ending the reaction after 0.5h to 1.5h, so that the polymerized polyol and isophorone diisocyanate complete the polymerization reaction more quickly under the action of the catalyst to obtain a polyurethane prepolymer having terminal isocyanate groups.

[0041] S102. Use a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid to carry out a chain extension reaction on the terminal isocyanate group-containing polyurethane prepolymer to obtain a highly conductive formaldehyde-free polyurethane adhesive for leather goods containing imidazole heterocyclic ionic liquid; wherein the chain extension reaction conditions are: reaction temperature of 70°C~85°C, reaction time of 2h~4h, and stirring speed of 200 r / min~400 r / min.

[0042] It can be understood that since the piperazine in the piperazine heterocyclic dispersion is a large sterically hindered diamine, the added large sterically hindered diamine can construct a hindered urea bond with the polyurethane prepolymer with an isocyanate terminal, so that the hindered urea bond can be decomposed into amine and isocyanate under specific conditions (neutral conditions and the presence of a simple nucleophilic reagent), thereby achieving a self-healing effect on the leather material, and the dynamic properties of the hindered urea bond can form an interpenetrating network structure similar to "hand in hand" inside the leather material, thereby enhancing the internal structure of the leather material, bringing more hydrogen bonds, and thereby improving the bonding strength of the formaldehyde-free polyurethane adhesive for highly conductive leather containing imidazole heterocyclic ionic liquids.

[0043] It can also be understood that since the imidazolium heterocyclic ionic liquid contains both substituted imidazole cations and fluorinated sulfonyl imide anions, on the one hand, the added imidazolium heterocyclic ionic liquid can form an ion exchange channel that mimics the cell membrane material exchange to improve the ion migration performance, thereby achieving the combination of excellent bonding performance and excellent electrical properties of the formaldehyde-free polyurethane adhesive for high-conductivity leather goods containing imidazolium heterocyclic ionic liquids, and improving its antibacterial properties to better adapt to the application of high-conductivity multifunctional leather products; on the other hand, the ion pairs in the imidazolium heterocyclic ionic liquid can reduce the number of free isocyanate groups to ensure that the isocyanate groups can react completely, thereby improving the imidazolium heterocyclic ionic liquid. The bonding strength of the liquid high-conductivity formaldehyde-free polyurethane adhesive for leather goods; on the other hand, the imidazole heterocyclic ionic liquid has a lower viscosity, which can change the fluidity of the polyurethane molecular chain in the polyurethane structure containing hindered urea bonds, making the processing difficulty lower, and effectively avoiding processing problems such as sticking to the board during processing; on the other hand, the addition of the imidazole heterocyclic ionic liquid can reduce the amount of organic solvent used, effectively avoiding the excessive amount of organic solvent used in traditional leather goods, resulting in excessive residual amount and affecting human health; on the other hand, the fluorinated sulfonyl imide anion containing the imidazole heterocyclic ionic liquid has a certain nucleophilicity, which accelerates the self-repair rate of the leather material to achieve rapid self-repair of the leather material.

[0044] It can also be understood that if the temperature of the chain extension reaction is less than 70°C or the reaction time is less than 2h, the piperazine heterocyclic dispersion, the imidazole heterocyclic ionic liquid and the isocyanate-terminated polyurethane prepolymer will not react completely. If the temperature of the chain extension reaction is greater than 85°C or the reaction time is greater than 4h, the viscosity of the entire reaction system will be too high, resulting in a more serious problem of sticking. Therefore, in the present disclosure, by controlling the reaction temperature to 70°C to 85°C and the reaction time to 2h to 4h, the piperazine heterocyclic dispersion, the imidazole heterocyclic ionic liquid and the isocyanate-terminated polyurethane prepolymer are ensured to react completely, and at the same time, the viscosity of the entire reaction system is not too high, that is, the fluidity is good, thereby effectively avoiding the problem of sticking.

[0045] It can also be understood that if the stirring speed is lower than 200 r / min, the sufficiency of the reaction of the piperazine heterocyclic dispersion, the imidazole heterocyclic ionic liquid and the terminal isocyanate polyurethane prepolymer cannot be guaranteed. If the stirring speed is higher than 400 r / min, the excessive stirring shear force will destroy the molecular chain of the polyurethane structure containing the hindered urea bond, resulting in the bonding strength of the formaldehyde-free polyurethane adhesive for high-conductivity leather goods containing the imidazole heterocyclic ionic liquid. Therefore, in the present disclosure, by controlling the stirring speed to 200 r / min~400 r / min, especially with the reaction temperature of 70℃~85℃ and the reaction time of 2h~4h, it is ensured that the formaldehyde-free polyurethane adhesive for high-conductivity leather goods containing the imidazole heterocyclic ionic liquid with excellent bonding strength, antibacterial properties, self-repairing, non-sticky board, and low organic solvent residue is prepared.

[0046] The preparation method of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids, because piperazine heterocyclic dispersion and imidazole heterocyclic ionic liquids are cited, the added piperazine heterocyclic dispersion helps to construct hindered urea bonds to achieve a self-repairing effect on leather materials, and the formed hindered urea bonds can improve the bonding strength of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids, and the added imidazole heterocyclic ionic liquids are beneficial to improving the conductivity, bonding performance, and antibacterial properties of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids, and reducing the residual amount of organic solvents, and the addition of imidazole heterocyclic ionic liquids changes the fluidity of the polyurethane molecular chain in the polyurethane structure containing hindered urea bonds, avoiding processing problems such as sticking to the board during processing, thereby reducing the processing difficulty.

[0047] It can be understood that if the imidazole heterocyclic ionic liquid is added first and then the piperazine heterocyclic dispersion liquid is added, the imidazole heterocyclic ionic liquid added first will react with the terminal isocyanate polyurethane prepolymer first, which is not conducive to the construction of the main chain of the polyurethane structure containing hindered urea bonds. Therefore, in one embodiment, the step of using the piperazine heterocyclic dispersion liquid and the imidazole heterocyclic ionic liquid to perform a chain extension reaction on the terminal isocyanate polyurethane prepolymer includes the following specific steps: when the terminal isocyanate polyurethane prepolymer is heated to 70°C~85°C, the piperazine heterocyclic dispersion liquid is slowly added to the terminal isocyanate polyurethane prepolymer within 1h~2h, and then the temperature is kept at 70°C~85°C, and the imidazole heterocyclic ionic liquid is slowly added to the terminal isocyanate polyurethane prepolymer. The reaction is continued for 1h~2h to ensure that the large sterically hindered dibasic secondary amine in the added piperazine heterocyclic dispersion constructs a hindered urea bond, which is conducive to the formation of the dynamic properties of the hindered urea bond, that is, an interpenetrating network structure similar to "hand in hand" is formed inside the leather material, thereby enhancing the internal structure of the leather material, and then the low-viscosity imidazole heterocyclic ionic liquid added can change the fluidity of the polyurethane molecular chain in the polyurethane structure containing hindered urea bonds, making the processing difficulty lower, and effectively avoiding processing problems such as sticking to the board during the processing. At the same time, with an appropriate stirring speed, it is ensured that a formaldehyde-free polyurethane adhesive for leather with high conductivity containing imidazole heterocyclic ionic liquid with excellent bonding strength, antibacterial properties, self-repairing, non-stickiness, and low organic solvent residue is prepared.

[0048] In one embodiment, the polymeric polyol includes at least one of polytetramethylene glycol, polybutylene adipate, polycarbonate diol and polypropylene glycol.

[0049] In one embodiment, the catalyst includes at least one of dibutyltin dilaurate, bismuth acetate, bismuth acetylacetonate, dimethylcyclohexylamine and N,N-dimethylbenzylamine.

[0050] In one embodiment, the polymeric polyol and the isophorone diisocyanate are used in a molar ratio of 1:3, especially when the molecular weight of the polymeric polyol is 1000-1200, so as to ensure the preparation of a polyurethane prepolymer with terminal isocyanate groups of suitable molecular weight.

[0051] It can be understood that if polytetrahydrofuran and polybutylene adipate are used alone, they cannot form a sufficient number and strength of hindered urea bonds, resulting in the low bonding strength and poor self-healing effect of the aldehyde-free polyurethane adhesive for leather goods containing imidazole heterocyclic ionic liquids. Therefore, in a preferred embodiment, the polymeric polyol is a mixture of polytetrahydrofuran and polybutylene adipate, and the molar ratio of polytetrahydrofuran and polybutylene adipate is 4:1, the reaction temperature is 80°C, and the reaction time is 2h, so as to ensure that the added polytetrahydrofuran and polybutylene adipate can form their own cross-linked networks with the terminal isocyanate polyurethane prepolymer, and these cross-linked networks will interweave and entangle with each other in space to form an interpenetrating network structure, so that an interpenetrating network structure similar to "hand in hand" can be formed inside the leather material, thereby enhancing the internal structure of the leather material.

[0052] It can also be understood that since polytetrahydrofuran has good softness, that is, the soft segment, and polybutylene adipate has good rigidity, that is, the hard segment, therefore, by controlling the molar ratio of polytetrahydrofuran and polybutylene adipate to 4:1, it is helpful to prepare a formaldehyde-free polyurethane adhesive for leather goods containing imidazole heterocyclic ionic liquids with suitable hardness and softness, excellent weather resistance, ideal process performance, antibacterial ability, high bonding life, high conductivity, and self-healing.

[0053] In one embodiment, the piperazine-containing heterocyclic dispersion includes at least one of (±)piperazine-2-carboxylic acid dispersion, 1-carboxymethylpiperazine dispersion, N-carboxyethylpiperazine dispersion, N,N'-dicarboxyethylpiperazine dispersion and piperazine-1,4-dicarboxylic acid dispersion, to ensure that the piperazine of the added piperazine-containing heterocyclic dispersion is a large sterically hindered divalent secondary amine, which helps to construct a hindered urea bond.

[0054] In one embodiment, the (±)piperazine-2-carboxylic acid dispersion is a mixture of (±)piperazine-2-carboxylic acid and an amide organic solvent.

[0055] It can be understood that, compared with the increased steric hindrance effect of the piperazine ring in 1-carboxymethylpiperazine dispersion, N-carboxyethylpiperazine dispersion, N,N'-dicarboxyethylpiperazine dispersion and piperazine-1,4-dicarboxylic acid dispersion, since the piperazine ring in the (±)piperazine-2-carboxylic acid dispersion has a certain spatial configuration, this configuration enables the (±)piperazine-2-carboxylic acid dispersion to effectively reduce the steric hindrance effect in the chain extension reaction, that is, the piperazine ring in the (±)piperazine-2-carboxylic acid dispersion has a reduced steric hindrance effect; thereby facilitating the formation of hindered urea bonds, and further facilitating the construction of hindered urea bonds with dynamic properties.

[0056] It can also be understood that, due to the poor dispersibility of (±)piperazine-2-carboxylic acid in the polyurethane prepolymer with terminal isocyanate groups, it is not conducive to the sufficient reaction of (±)piperazine-2-carboxylic acid with the polyurethane prepolymer with terminal isocyanate groups. Therefore, in the present disclosure, by mixing (±)piperazine-2-carboxylic acid with an amide organic solvent, the (±)piperazine-2-carboxylic acid can be well dispersed in a small amount of amide organic solvent, which is conducive to the preparation of a uniform and stable (±)piperazine-2-carboxylic acid dispersion, so as to ensure that the (±)piperazine-2-carboxylic acid fully reacts with the polyurethane prepolymer with terminal isocyanate groups, which is conducive to the construction of a hindered urea bond with dynamic properties.

[0057] It is understandable that if the amount of amide organic solvent added is too much, the residual amount of amide organic solvent will be too high and affect human health. Therefore, in one embodiment, the mass ratio of (±)piperazine-2-carboxylic acid and amide organic solvent is in the range of 0.02:0.26, so as to ensure that a uniform and stable (±)piperazine-2-carboxylic acid dispersion can be prepared by adding a small amount of amide organic solvent, and the residual amount of amide organic solvent is reduced.

[0058] In one embodiment, the amide organic solvent includes at least one of N,N-dimethylformamide, N,N-dimethylformamide and dimethyl sulfoxide.

[0059] In a preferred embodiment, the amide organic solvent is N,N-dimethylformamide.

[0060] It can be understood that if the amount of (±) piperazine-2-carboxylic acid added is too much, it will cause the problem of waste of (±) piperazine-2-carboxylic acid. If the amount of (±) piperazine-2-carboxylic acid added is too little, the -NCO group will not react completely, which will affect the construction of the hindered urea bond. Therefore, in one embodiment, by controlling the molar ratio of (±) piperazine-2-carboxylic acid in the (±) piperazine-2-carboxylic acid dispersion to -NCO in the isocyanate-terminated polyurethane prepolymer to be (1~5):10, it is ensured that the added (±) piperazine-2-carboxylic acid can react completely and efficiently with -NCO, thereby constructing a stable and efficient hindered urea bond, which is helpful to prepare a "hand-in-hand" interpenetrating network structure containing a hindered urea bond polyurethane structure.

[0061] In one embodiment, the -NCO content in the isocyanate-terminated polyurethane prepolymer is measured by a toluene di-n-butylamine method.

[0062] It can be understood that if the amount of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid added is too much, the interaction between ions is enhanced to affect the mobility and conductivity of the ions, resulting in the problem of poor conductivity of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazolium heterocyclic ionic liquids. If the amount of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid added is too little, the interaction between ions is weakened, resulting in a decrease in the mobility of the ions and affecting the conductivity of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazolium heterocyclic ionic liquids. Therefore, in one embodiment, the mass ratio of the 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid to the isocyanate-terminated polyurethane prepolymer is (13-120):100, so as to ensure that the ion concentration of the added 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid is more appropriate, thereby ensuring the preparation of a highly conductive formaldehyde-free polyurethane adhesive for leather goods containing highly conductive imidazole heterocyclic ionic liquid.

[0063] Compared with the prior art, the present invention has at least the following advantages: 1) Since the hindered urea bond in the polyurethane structure containing hindered urea bonds can be decomposed into amines and isocyanates under specific conditions (neutral conditions and the presence of simple nucleophiles), the self-healing effect on the leather material can be achieved; and the dynamic properties of the hindered urea bonds in the polyurethane structure containing hindered urea bonds can form an interpenetrating network structure similar to "hand in hand" inside the leather material, thereby enhancing the internal structure of the leather material, bringing more hydrogen bonds, and thus improving the bonding strength of the formaldehyde-free polyurethane adhesive for highly conductive leather containing imidazolium heterocyclic ionic liquids; and since the nitrogen atom on the imidazole ring in the substituted imidazole cation carries a positive charge, while the fluorinated sulfonyl imide anion carries a negative charge, it is beneficial to the migration of charges in the polyurethane structure; thereby improving the conductivity of the formaldehyde-free polyurethane adhesive for highly conductive leather containing imidazolium heterocyclic ionic liquids; compared with traditional For ionic liquids of halogen ions, the substituents introduced into the substituted imidazole cations can effectively adjust their charge distribution and ionic radius. In addition, the fluorinated sulfonyl imide anions have strong electronegativity and small size, which further optimizes the ion conductivity. In addition, the interaction between the substituted imidazole cations and the fluorinated sulfonyl imide anions is weak, which makes the ion conduction efficiency in the polyurethane structure higher, thereby ensuring that the prepared formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids has high conductivity, that is, the ion exchange channels are constructed by imitating the cell membrane material exchange to improve the ion migration performance, thereby achieving the combination of excellent bonding performance and excellent electrical properties of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids, and improving its antibacterial properties to better adapt to the application of highly conductive multifunctional leather products.

[0064] 2) Since substituted imidazole cations and fluorinated sulfonyl imide anions can form ion pairs, and these ion pairs can affect the distribution and activity of isocyanate groups through electrostatic interactions or steric hindrance effects, the number of free isocyanate groups is reduced to ensure that the isocyanate groups can react completely, thereby improving the bonding strength of the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquids, effectively avoiding the problem of low adhesion caused by the high number of free isocyanate groups in traditional formaldehyde polyurethane adhesives due to the high chemical activity of isocyanate groups.

[0065] 3) Since the ionic liquid formed by the substituted imidazole cation and the fluorinated sulfonyl imide anion has a low viscosity, when it is introduced into the polyurethane structure containing hindered urea bonds, the fluidity of the polyurethane molecular chain in the polyurethane structure containing hindered urea bonds can be changed, effectively avoiding processing problems such as sticking to the board that are prone to occur during the processing.

[0066] 4) Since the fluorinated sulfonyl imide anions have a certain nucleophilicity, mainly because the fluorinated group has a strong electron-withdrawing effect, thereby reducing the negative charge density of the fluorinated sulfonyl imide anions, and the fluorinated alkyl group also has a certain degree of steric hindrance effect, so that the fluorinated sulfonyl imide anions exhibit weak coordination characteristics, and are easy to approach and attack the electrophilic part of the hindered urea bond, thereby accelerating the self-repair rate of the leather material, so as to achieve rapid self-repair of the leather material.

[0067] 5) Due to the introduction of substituted imidazole cations and fluorinated sulfonyl imide anions, the use of organic solvents is reduced, effectively avoiding the excessive residual amount of organic solvents in traditional leather goods that affects human health.

[0068] Some specific examples are given below, and if % is mentioned, it means percentage by weight. It should be noted that the following examples do not exhaust all possible situations, and the materials used in the following examples can be obtained from commercial sources unless otherwise specified.

[0069] Among them, isophorone diisocyanate was provided by Shanghai McLean Chemical Reagent Co., Ltd. with the model number I811865, polytetrahydrofuran was provided by Shanghai McLean Chemical Reagent Co., Ltd. with the model number P816810, dibutyltin dilaurate was provided by Shanghai McLean Chemical Reagent Co., Ltd. with the model number D806313, (±)piperazine-2-carboxylic acid was provided by Shanghai Titan Technology Co., Ltd. with the model number 44144C, N,N-dimethylformamide was provided by Shanghai McLean Chemical Reagent Co., Ltd. with the model number N807505, and 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide ionic liquid was provided by Shanghai McLean Chemical Reagent Co., Ltd. with the model number E837161.

[0070] Example 1 Step 1: Prepare isocyanate-terminated polyurethane prepolymer 15 mmol of isophorone diisocyanate, 5 mmol of polytetrahydrofuran (Mn~1000), and 0.1 g of dibutyltin dilaurate (DBTDL) catalyst were added into a three-necked flask equipped with a stirrer and a glass stopper and mixed evenly at a stirring speed of 300 r / min. The mixture was heated with a heat-collecting constant temperature heating magnetic stirrer (oil bath) under a nitrogen atmosphere. The reaction was initially carried out at 55°C for 30 minutes, then the temperature was raised to 65°C. The reaction was continued for 30 minutes, then the temperature was raised to 75°C. After the reaction was completed for 1 hour, the prepolymerization was completed to obtain a polyurethane prepolymer with terminal isocyanate groups.

[0071] Step 2: Preparation of a high-conductivity formaldehyde-free polyurethane adhesive for leather goods containing an imidazole heterocyclic ionic liquid by using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid The -NCO content in the terminal isocyanate polyurethane prepolymer was measured by the toluene di-n-butylamine method. When the reaction was close to the theoretical value and the -NCO content was 20 mmol, 10 mmol (±) piperazine-2-carboxylic acid was calculated and weighed and dispersed in 15 g N,N-dimethylformamide to obtain a (±) piperazine-2-carboxylic acid dispersion. The 75°C polyurethane prepolymer was heated to 80°C, and the (±) piperazine-2-carboxylic acid dispersion was slowly added dropwise at a stirring speed of 300 r / min. The addition was completed within 2 hours. 3 g 1-butyl-3-methylimidazole di(trifluoromethylsulfonyl)imide ionic liquid was added dropwise at a stirring speed of 300 r / min and 80°C, and the reaction was continued for 1 hour before the reaction was completed.

[0072] Example 2 Step 1: Prepare isocyanate-terminated polyurethane prepolymer 15mmol of isophorone diisocyanate, 5mmol of polybutylene adipate (Mn~1000), and 0.1g of dibutyltin dilaurate (DBTDL) catalyst were added into a three-necked flask equipped with a stirrer and a glass stopper and mixed evenly at a stirring speed of 300r / min. The mixture was heated with a heat-collecting constant temperature heating magnetic stirrer (oil bath) under a nitrogen atmosphere. The reaction was initially carried out at 55°C for 30min and then the temperature was raised to 65°C. The reaction was continued for 30min and then the temperature was raised to 75°C. After the reaction was completed for 1h, the prepolymerization was completed to obtain a polyurethane prepolymer with terminal isocyanate groups.

[0073] Step 2: Preparation of a high-conductivity formaldehyde-free polyurethane adhesive for leather goods containing an imidazole heterocyclic ionic liquid by using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid The -NCO content in the terminal isocyanate polyurethane prepolymer was measured by the toluene di-n-butylamine method. When the reaction was close to the theoretical value and the -NCO content was 20 mmol, 10 mmol (±) piperazine-2-carboxylic acid was calculated and weighed and dispersed in 14 g N,N-dimethylformamide to obtain a (±) piperazine-2-carboxylic acid dispersion. The 75°C polyurethane prepolymer was heated to 80°C, and the (±) piperazine-2-carboxylic acid dispersion was slowly added dropwise at a stirring speed of 300 r / min. The addition was completed within 2 hours. 3 g 1-butyl-3-methylimidazole di(trifluoromethylsulfonyl)imide ionic liquid was added dropwise at a stirring speed of 300 r / min and 80°C, and the reaction was continued for 1 hour before the reaction was completed.

[0074] Example 3 Step 1: Prepare isocyanate-terminated polyurethane prepolymer 15mmol of isophorone diisocyanate, 4mmol of polytetrahydrofuran (Mn~1000), 1mmol of polybutylene adipate (Mn~1000), and 0.1g of dibutyltin dilaurate (DBTDL) catalyst were added into a three-necked flask equipped with a stirrer and a glass stopper and mixed evenly at a stirring speed of 300r / min. The mixture was heated with a heat-collecting constant temperature heating magnetic stirrer (oil bath) under a nitrogen atmosphere. The mixture was initially reacted at 55°C for 30min and then heated to 65°C. The reaction was continued for 30min and then heated to 75°C. After the reaction was completed for 1h, the prepolymerization was completed to obtain a polyurethane prepolymer with terminal isocyanate groups.

[0075] Step 2: Preparation of a high-conductivity formaldehyde-free polyurethane adhesive for leather goods containing an imidazole heterocyclic ionic liquid by using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid The -NCO content in the terminal isocyanate polyurethane prepolymer was measured by the toluene di-n-butylamine method. When the reaction was close to the theoretical value and the -NCO content was 20 mmol, 10 mmol (±) piperazine-2-carboxylic acid was calculated and weighed and dispersed in 13 g N,N-dimethylformamide to obtain a (±) piperazine-2-carboxylic acid dispersion. The 75°C polyurethane prepolymer was heated to 80°C, and the (±) piperazine-2-carboxylic acid dispersion was slowly added dropwise at a stirring speed of 300 r / min. The addition was completed within 2 hours. 3 g 1-butyl-3-methylimidazole di(trifluoromethylsulfonyl)imide ionic liquid was added dropwise at a stirring speed of 300 r / min and 80°C, and the reaction was continued for 1 hour before the reaction was completed.

[0076] Example 4 Step 1: Prepare isocyanate-terminated polyurethane prepolymer 15mmol of isophorone diisocyanate, 4mmol of polytetrahydrofuran (Mn~1000), 1mmol of polybutylene adipate (Mn~1000), and 0.1g of dibutyltin dilaurate (DBTDL) catalyst were added into a three-necked flask equipped with a stirrer and a glass stopper and mixed evenly at a stirring speed of 300r / min. The mixture was heated with a heat-collecting constant temperature heating magnetic stirrer (oil bath) under a nitrogen atmosphere. The mixture was initially reacted at 55°C for 30min and then heated to 65°C. The reaction was continued for 30min and then heated to 75°C. After the reaction was completed for 1h, the prepolymerization was completed to obtain a polyurethane prepolymer with terminal isocyanate groups.

[0077] Step 2: Preparation of a high-conductivity formaldehyde-free polyurethane adhesive for leather goods containing an imidazole heterocyclic ionic liquid by using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid The -NCO content in the terminal isocyanate polyurethane prepolymer was measured by the toluene di-n-butylamine method. When the reaction was close to the theoretical value and the -NCO content was 20 mmol, 2 mmol (±) piperazine-2-carboxylic acid was calculated and weighed and dispersed in 12 g N,N-dimethylformamide to obtain a (±) piperazine-2-carboxylic acid dispersion. The 75°C polyurethane prepolymer was heated to 80°C. Under the condition of stirring at a speed of 300 r / min, the (±) piperazine-2-carboxylic acid dispersion was slowly added dropwise. The addition was completed within 1 hour. Then 8 mmol of a small molecule chain extender 1,4-butanediol was weighed and added to a three-necked flask for chain extension for 1 hour. Under the condition of maintaining a stirring speed of 300 r / min and 80°C, 3 g of 1-butyl-3-methylimidazole di(trifluoromethylsulfonyl)imide ionic liquid was added dropwise and the reaction was continued for 1 hour before the reaction was completed.

[0078] Example 5 Step 1: Prepare isocyanate-terminated polyurethane prepolymer 15mmol of isophorone diisocyanate, 4mmol of polytetrahydrofuran (Mn~1000), 1mmol of polybutylene adipate (Mn~1000), and 0.1g of dibutyltin dilaurate (DBTDL) catalyst were added into a three-necked flask equipped with a stirrer and a glass stopper and mixed evenly at a stirring speed of 300r / min. The mixture was heated with a heat-collecting constant temperature heating magnetic stirrer (oil bath) under a nitrogen atmosphere. The mixture was initially reacted at 55°C for 30min and then heated to 65°C. The reaction was continued for 30min and then heated to 75°C. After the reaction was completed for 1h, the prepolymerization was completed to obtain a polyurethane prepolymer with terminal isocyanate groups.

[0079] Step 2: Preparation of a high-conductivity formaldehyde-free polyurethane adhesive for leather goods containing an imidazole heterocyclic ionic liquid by using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid The -NCO content in the terminal isocyanate polyurethane prepolymer was measured by the toluene di-n-butylamine method. When the reaction was close to the theoretical value and the -NCO content was 20 mmol, 4 mmol (±) piperazine-2-carboxylic acid was calculated and weighed and dispersed in 11 g N,N-dimethylformamide to obtain a (±) piperazine-2-carboxylic acid dispersion. The 75°C polyurethane prepolymer was heated to 80°C. Under the condition of stirring at a speed of 300 r / min, the (±) piperazine-2-carboxylic acid dispersion was slowly added dropwise. The addition was completed within 1 hour. Then 6 mmol of a small molecule chain extender 1,4-butanediol was weighed and added to a three-necked flask for chain extension for 1 hour. Under the condition of maintaining a stirring speed of 300 r / min and 80°C, 3 g of 1-butyl-3-methylimidazole di(trifluoromethylsulfonyl)imide ionic liquid was added dropwise and the reaction was continued for 1 hour before the reaction was completed.

[0080] Example 6 Step 1: Prepare isocyanate-terminated polyurethane prepolymer 15mmol of isophorone diisocyanate, 4mmol of polytetrahydrofuran (Mn~1000), 1mmol of polybutylene adipate (Mn~1000), and 0.1g of dibutyltin dilaurate (DBTDL) catalyst were added into a three-necked flask equipped with a stirrer and a glass stopper and mixed evenly at a stirring speed of 300r / min. The mixture was heated with a heat-collecting constant temperature heating magnetic stirrer (oil bath) under a nitrogen atmosphere. The mixture was initially reacted at 55°C for 30min and then heated to 65°C. The reaction was continued for 30min and then heated to 75°C. After the reaction was completed for 1h, the prepolymerization was completed to obtain a polyurethane prepolymer with terminal isocyanate groups.

[0081] Step 2: Preparation of a high-conductivity formaldehyde-free polyurethane adhesive for leather goods containing an imidazole heterocyclic ionic liquid by using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid The -NCO content in the terminal isocyanate polyurethane prepolymer was measured by the toluene di-n-butylamine method. When the reaction was close to the theoretical value and the -NCO content was 20 mmol, 6 mmol (±) piperazine-2-carboxylic acid was calculated and weighed and dispersed in 10 g N,N-dimethylformamide to obtain a (±) piperazine-2-carboxylic acid dispersion. The 75°C polyurethane prepolymer was heated to 80°C. Under the condition of stirring at a speed of 300 r / min, the (±) piperazine-2-carboxylic acid dispersion was slowly added dropwise. The addition was completed within 1 hour. Then 4 mmol of a small molecule chain extender 1,4-butanediol was weighed and added to a three-necked flask for chain extension for 1 hour. Under the condition of maintaining a stirring speed of 300 r / min and 80°C, 3 g of 1-butyl-3-methylimidazole di(trifluoromethylsulfonyl)imide ionic liquid was added dropwise and the reaction was continued for 1 hour before the reaction was completed.

[0082] Example 7 Step 1: Prepare isocyanate-terminated polyurethane prepolymer 15mmol of isophorone diisocyanate, 4mmol of polytetrahydrofuran (Mn~1000), 1mmol of polybutylene adipate (Mn~1000), and 0.1g of dibutyltin dilaurate (DBTDL) catalyst were added into a three-necked flask equipped with a stirrer and a glass stopper and mixed evenly at a stirring speed of 300r / min. The mixture was heated with a heat-collecting constant temperature heating magnetic stirrer (oil bath) under a nitrogen atmosphere. The mixture was initially reacted at 55°C for 30min and then heated to 65°C. The reaction was continued for 30min and then heated to 75°C. After the reaction was completed for 1h, the prepolymerization was completed to obtain a polyurethane prepolymer with terminal isocyanate groups.

[0083] Step 2: Preparation of a high-conductivity formaldehyde-free polyurethane adhesive for leather goods containing an imidazole heterocyclic ionic liquid by using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid The -NCO content in the terminal isocyanate polyurethane prepolymer was measured by the toluene di-n-butylamine method. When the reaction was close to the theoretical value and the -NCO content was 20 mmol, 8 mmol (±) piperazine-2-carboxylic acid was calculated and weighed and dispersed in 9 g N,N-dimethylformamide to obtain a (±) piperazine-2-carboxylic acid dispersion. The 75°C polyurethane prepolymer was heated to 80°C and the (±) piperazine-2-carboxylic acid dispersion was slowly added dropwise at a stirring speed of 300 r / min. The addition was completed within 1 hour. Then 2 mmol of a small molecule chain extender 1,4-butanediol was weighed and added to a three-necked flask for chain extension for 1 hour. 3 g of 1-butyl-3-methylimidazole di(trifluoromethylsulfonyl)imide ionic liquid was added dropwise at a stirring speed of 300 r / min and 80°C to continue the reaction for 1 hour before the reaction was completed.

[0084] Example 8 Step 1: Prepare isocyanate-terminated polyurethane prepolymer 15mmol of isophorone diisocyanate, 4mmol of polytetrahydrofuran (Mn~1000), 1mmol of polybutylene adipate (Mn~1000), and 0.1g of dibutyltin dilaurate (DBTDL) catalyst were added into a three-necked flask equipped with a stirrer and a glass stopper and mixed evenly at a stirring speed of 300r / min. The mixture was heated with a heat-collecting constant temperature heating magnetic stirrer (oil bath) under a nitrogen atmosphere. The mixture was initially reacted at 55°C for 30min and then heated to 65°C. The reaction was continued for 30min and then heated to 75°C. After the reaction was completed for 1h, the prepolymerization was completed to obtain a polyurethane prepolymer with terminal isocyanate groups.

[0085] Step 2: Preparation of a high-conductivity formaldehyde-free polyurethane adhesive for leather goods containing an imidazole heterocyclic ionic liquid by using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid The -NCO content in the terminal isocyanate polyurethane prepolymer was measured by the toluene di-n-butylamine method. When the reaction was close to the theoretical value and the -NCO content was 20 mmol, 10 mmol (±) piperazine-2-carboxylic acid was calculated and weighed and dispersed in 13 g N,N-dimethylformamide to obtain a (±) piperazine-2-carboxylic acid dispersion. The 75°C polyurethane prepolymer was heated to 80°C, and the (±) piperazine-2-carboxylic acid dispersion was slowly added dropwise at a stirring speed of 300 r / min. The addition was completed within 2 hours. 1.1 g 1-butyl-3-methylimidazole di(trifluoromethylsulfonyl)imide ionic liquid was added dropwise at a stirring speed of 300 r / min and 80°C, and the reaction was terminated after continuing to react for 1 hour.

[0086] Example 9 Step 1: Prepare isocyanate-terminated polyurethane prepolymer 15mmol of isophorone diisocyanate, 4mmol of polytetrahydrofuran (Mn~1000), 1mmol of polybutylene adipate (Mn~1000), and 0.1g of dibutyltin dilaurate (DBTDL) catalyst were added into a three-necked flask equipped with a stirrer and a glass stopper and mixed evenly at a stirring speed of 300r / min. The mixture was heated with a heat-collecting constant temperature heating magnetic stirrer (oil bath) under a nitrogen atmosphere. The mixture was initially reacted at 55°C for 30min and then heated to 65°C. The reaction was continued for 30min and then heated to 75°C. After the reaction was completed for 1h, the prepolymerization was completed to obtain a polyurethane prepolymer with terminal isocyanate groups.

[0087] Step 2: Preparation of a high-conductivity formaldehyde-free polyurethane adhesive for leather goods containing an imidazole heterocyclic ionic liquid by using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid The -NCO content in the terminal isocyanate polyurethane prepolymer was measured by the toluene di-n-butylamine method. When the reaction was close to the theoretical value and the -NCO content was 20 mmol, 10 mmol (±) piperazine-2-carboxylic acid was calculated and weighed and dispersed in 12 g N,N-dimethylformamide to obtain a (±) piperazine-2-carboxylic acid dispersion. The 75°C polyurethane prepolymer was heated to 80°C, and the (±) piperazine-2-carboxylic acid dispersion was slowly added dropwise at a stirring speed of 300 r / min. The addition was completed within 2 hours. 2.5 g 1-butyl-3-methylimidazole di(trifluoromethylsulfonyl)imide ionic liquid was added dropwise at a stirring speed of 300 r / min and 80°C, and the reaction was terminated after continuing to react for 1 hour.

[0088] Example 10 Step 1: Prepare isocyanate-terminated polyurethane prepolymer 15mmol of isophorone diisocyanate, 4mmol of polytetrahydrofuran (Mn~1000), 1mmol of polybutylene adipate (Mn~1000), and 0.1g of dibutyltin dilaurate (DBTDL) catalyst were added into a three-necked flask equipped with a stirrer and a glass stopper and mixed evenly at a stirring speed of 300r / min. The mixture was heated with a heat-collecting constant temperature heating magnetic stirrer (oil bath) under a nitrogen atmosphere. The mixture was initially reacted at 55°C for 30min and then heated to 65°C. The reaction was continued for 30min and then heated to 75°C. After the reaction was completed for 1h, the prepolymerization was completed to obtain a polyurethane prepolymer with terminal isocyanate groups.

[0089] Step 2: Preparation of a high-conductivity formaldehyde-free polyurethane adhesive for leather goods containing an imidazole heterocyclic ionic liquid by using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid The -NCO content in the terminal isocyanate polyurethane prepolymer was measured by the toluene di-n-butylamine method. When the reaction was close to the theoretical value and the -NCO content was 20 mmol, 10 mmol (±) piperazine-2-carboxylic acid was calculated and weighed and dispersed in 10 g N,N-dimethylformamide to obtain a (±) piperazine-2-carboxylic acid dispersion. The 75°C polyurethane prepolymer was heated to 80°C, and the (±) piperazine-2-carboxylic acid dispersion was slowly added dropwise at a stirring speed of 300 r / min. The addition was completed within 2 hours. 4.3 g 1-butyl-3-methylimidazole di(trifluoromethylsulfonyl)imide ionic liquid was added dropwise at a stirring speed of 300 r / min and 80°C, and the reaction was terminated after continuing to react for 1 hour.

[0090] Embodiment 11 Step 1: Prepare isocyanate-terminated polyurethane prepolymer 15mmol of isophorone diisocyanate, 4mmol of polytetrahydrofuran (Mn~1000), 1mmol of polybutylene adipate (Mn~1000), and 0.1g of dibutyltin dilaurate (DBTDL) catalyst were added into a three-necked flask equipped with a stirrer and a glass stopper and mixed evenly at a stirring speed of 300r / min. The mixture was heated with a heat-collecting constant temperature heating magnetic stirrer (oil bath) under a nitrogen atmosphere. The mixture was initially reacted at 55°C for 30min and then heated to 65°C. The reaction was continued for 30min and then heated to 75°C. After the reaction was completed for 1h, the prepolymerization was completed to obtain a polyurethane prepolymer with terminal isocyanate groups.

[0091] Step 2: Preparation of a high-conductivity formaldehyde-free polyurethane adhesive for leather goods containing an imidazole heterocyclic ionic liquid by using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid The -NCO content in the terminal isocyanate polyurethane prepolymer was measured by the toluene di-n-butylamine method. When the reaction was close to the theoretical value and the -NCO content was 20 mmol, 10 mmol (±) piperazine-2-carboxylic acid was calculated and weighed and dispersed in 9 g N,N-dimethylformamide to obtain a (±) piperazine-2-carboxylic acid dispersion. The 75°C polyurethane prepolymer was heated to 80°C, and the (±) piperazine-2-carboxylic acid dispersion was slowly added dropwise at a stirring speed of 300 r / min. The addition was completed within 2 hours. 6.6 g 1-butyl-3-methylimidazole di(trifluoromethylsulfonyl)imide ionic liquid was added dropwise at a stirring speed of 300 r / min and 80°C, and the reaction was continued for 1 hour before the reaction was completed.

[0092] Example 12 Step 1: Prepare isocyanate-terminated polyurethane prepolymer 15mmol of isophorone diisocyanate, 4mmol of polytetrahydrofuran (Mn~1000), 1mmol of polybutylene adipate (Mn~1000), and 0.1g of dibutyltin dilaurate (DBTDL) catalyst were added into a three-necked flask equipped with a stirrer and a glass stopper and mixed evenly at a stirring speed of 300r / min. The mixture was heated with a heat-collecting constant temperature heating magnetic stirrer (oil bath) under a nitrogen atmosphere. The mixture was initially reacted at 55°C for 30min and then heated to 65°C. The reaction was continued for 30min and then heated to 75°C. After the reaction was completed for 1h, the prepolymerization was completed to obtain a polyurethane prepolymer with terminal isocyanate groups.

[0093] Step 2: Preparation of a high-conductivity formaldehyde-free polyurethane adhesive for leather goods containing an imidazole heterocyclic ionic liquid by using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid The -NCO content in the terminal isocyanate polyurethane prepolymer was measured by the toluene di-n-butylamine method. When the reaction was close to the theoretical value and the -NCO content was 20 mmol, 10 mmol (±) piperazine-2-carboxylic acid was calculated and weighed and dispersed in 5 g N,N-dimethylformamide to obtain a (±) piperazine-2-carboxylic acid dispersion. The 75°C polyurethane prepolymer was heated to 80°C, and the (±) piperazine-2-carboxylic acid dispersion was slowly added dropwise at a stirring speed of 300 r / min. The addition was completed within 2 hours. 10 g 1-butyl-3-methylimidazole di(trifluoromethylsulfonyl)imide ionic liquid was added dropwise at a stirring speed of 300 r / min and 80°C, and the reaction was continued for 1 hour before the reaction was completed.

[0094] The formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid prepared in Examples 1 to 12 above was applied to leather goods, and the leather goods were tested for conductivity, self-repairing, bonding strength, and antibacterial properties, and the experimental data in the following table were obtained: Conductivity test: Use a multimeter to measure the material resistance, cut the test sample into a suitable size, check whether the multimeter can work properly, and connect the test line to the corresponding port of the multimeter or resistance meter. Usually, the red test line is connected to the "VΩmA" port and the black test line is connected to the "COM" port. Touch the probes of the test line to the two ends of the measured resistor respectively to ensure good contact. Read the displayed value on the multimeter or resistance meter, which is the value of the measured resistor. After the measurement is completed, record the measurement results in time. For important measurements, it is recommended to make multiple measurements and take the average value.

[0095] Self-healing test: Cut the sample into a suitable size and place it on a glass plate. Use a single-sided blade to cut it in the middle. Then apply a force of about 5N to the crack to make it in close contact. Heal it at a certain temperature and observe whether the sample can heal.

[0096] Bonding strength: Test the bonding strength of materials according to GB / T 2791-1995 standard.

[0097] Antibacterial performance: Antibacterial test was carried out according to QB / T 4341-2012 standard antibacterial performance test method.

[0098] Detection of residual N,N-dimethylformamide: Determine the residual amount of N,N-dimethylformamide in the bonding and curing samples according to QB / T 5158-2017.

[0099] Table 1 Experimental data It can be seen from Table 1 that in the above embodiments 1 to 12, the resistance of the samples in the conductivity test is 2.37×10 5 Ω~1.3×10 7 Ω, all can be self-repaired, bonding strength ≥1.7MPa, antibacterial performance ≥78%, residual amount of N,N-dimethylformamide <100mg / Kg, among which, the comprehensive indicators of Example 3 are the best.

[0100] The above-mentioned embodiments only express several implementation methods of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the disclosed patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the disclosed patent shall be subject to the attached claims.

Claims

1. A formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid, characterized in that: The formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid comprises a polyurethane structure containing a hindered urea bond, substituted imidazole cations and fluorine-containing sulfonyl imide anions.

2. The formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazolium heterocyclic ionic liquid according to claim 1, wherein the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazolium heterocyclic ionic liquid has the following structural formula: 。 3. A method for preparing a formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid, characterized in that: The steps include: obtaining a polyurethane prepolymer having terminal isocyanate groups; The isocyanate-terminated polyurethane prepolymer is subjected to a chain extension reaction using a piperazine heterocyclic dispersion and an imidazole heterocyclic ionic liquid to obtain a highly conductive formaldehyde-free polyurethane adhesive for leather goods containing imidazole heterocyclic ionic liquid; wherein the chain extension reaction conditions are as follows: the reaction temperature is 70°C to 85°C, the reaction time is 2h to 4h, and the stirring speed is 200 r / min to 400 r / min.

4. The method for preparing the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid according to claim 3, characterized in that: The step of obtaining a polyurethane prepolymer having terminal isocyanate groups includes the following specific steps: reacting a polymeric polyol, isophorone diisocyanate and a catalyst to synthesize a polyurethane prepolymer having terminal isocyanate groups; wherein the reaction conditions are: initially reacting at 55°C to 60°C for 20min to 30min, then heating to 65°C to 70°C, continuing to react for 20min to 30min, then heating to 75°C to 80°C, and ending the reaction after 0.5h to 1.5h.

5. The method for preparing the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid according to claim 4, characterized in that: The polymeric polyol comprises at least one of polytetrahydrofuran, polybutylene adipate, polycarbonate diol and polypropylene glycol; and / or, The catalyst comprises at least one of dibutyltin dilaurate, bismuth acetate, bismuth acetylacetonate, dimethylcyclohexylamine and N,N-dimethylbenzylamine; and / or, The polymeric polyol and the isophorone diisocyanate are used in a molar ratio of 1:3; and / or, The molecular weight of the polymeric polyol is 1000-1200.

6. The method for preparing the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid according to claim 3, characterized in that: The piperazine-containing heterocyclic dispersion includes at least one of (±)piperazine-2-carboxylic acid dispersion, 1-carboxymethylpiperazine dispersion, N-carboxyethylpiperazine dispersion, N,N'-dicarboxyethylpiperazine dispersion and piperazine-1,4-dicarboxylic acid dispersion.

7. The method for preparing the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid according to claim 6, characterized in that: The (±)piperazine-2-carboxylic acid dispersion is a mixture of (±)piperazine-2-carboxylic acid and an amide organic solvent.

8. The method for preparing the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid according to claim 6, characterized in that: The molar ratio of (±)piperazine-2-carboxylic acid in the (±)piperazine-2-carboxylic acid dispersion to -NCO in the isocyanate-terminated polyurethane prepolymer is (1-5):

10.

9. The method for preparing the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid according to claim 3, characterized in that: The imidazolium heterocyclic ionic liquid includes at least one of 1-butyl-3-methylimidazolium di(trifluoromethylsulfonyl)imide ionic liquid, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid, 1-propyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid and 1-pentyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid.

10. The method for preparing the formaldehyde-free polyurethane adhesive for highly conductive leather goods containing imidazole heterocyclic ionic liquid according to claim 9, characterized in that: The mass ratio of the 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide ionic liquid to the isocyanate-terminated polyurethane prepolymer is (13-120):100.

Images