Amino acid-based adhesive as well as preparation method and application thereof

Abstract

The invention provides an amino acid-based adhesive as well as a preparation method and application thereof, and the preparation method comprises the following steps: A) mixing small organic molecule super alkali with aldehyde, heating and stirring to obtain a eutectic solvent; the organic micromolecule super alkali comprises 1, 8-diazabicyclo [5.4. 0] undec-7-alkene and / or 1, 5-diazabicyclo [4.3. 0] nonyl-5-alkene, and the organic micromolecule super alkali comprises 1, 8-diazabicyclo [5.4. 0] undec-7-alkene and / or 1, 5 The aldehyde comprises one or more of vanillin, cinnamyl aldehyde and furfural; and B) mixing the eutectic solvent with amino acid, and heating for reaction to obtain the amino acid-based adhesive. Compared with traditional urea-formaldehyde resin, the amino acid-based adhesive prepared by the method is higher in bonding strength, a reliable way is provided for preparing green and safe plywood, a one-pot method is used for preparation, and the preparation process is simpler.

Description

Technical Field

[0001] The present invention belongs to the technical field of bio-based adhesives, and in particular relates to an amino acid-based adhesive, a preparation method and application thereof. Background Art

[0002] Urea-formaldehyde resin is a thermosetting resin synthesized from urea and formaldehyde. Due to its excellent bonding properties, low cost, and ease of processing, it is widely used in a variety of fields, including wood processing, wood-based panel manufacturing, textiles, and electrical insulation materials. Therefore, it is necessary to find environmentally friendly alternatives. Summary of the Invention

[0003] The purpose of the present invention is to provide an amino acid-based adhesive, a preparation method and application thereof. The amino acid-based adhesive of the present invention is safe and non-toxic and has higher bonding strength.

[0004] The present invention provides a method for preparing an amino acid-based adhesive, comprising the following steps:

[0005] A) mixing an organic small molecule superbase with an aldehyde, heating and stirring, to obtain a deep eutectic solvent;

[0006] The organic small molecule superbase includes 1,8-diazabicyclo[5.4.0]undec-7-ene and / or 1,5-diazabicyclo[4.3.0]non-5-ene;

[0007] The aldehyde includes one or more of vanillin, cinnamaldehyde and furfural;

[0008] B) mixing a deep eutectic solvent with an amino acid, and heating the mixture to react to obtain an amino acid-based adhesive.

[0009] Preferably, in step A), the molar ratio of aldehyde to organic small molecule superbase is (0.5-2):1.

[0010] Preferably, the temperature for heating and stirring in step A) is 70-120° C., and the time for heating and stirring in step A) is 15-40 min.

[0011] Preferably, the reaction in step A) is carried out under dry conditions.

[0012] Preferably, the deep eutectic solvent obtained in step A) is clear and transparent, and no crystals are precipitated after cooling to room temperature.

[0013] Preferably, the amino acids in step B) include one or more of tryptophan, lysine, phenylalanine, methionine, threonine, valine, leucine, isoleucine, cysteine, serine, glycine, tyrosine, aspartic acid, asparagine, glutamic acid, glutamine, alanine, arginine, histidine and proline.

[0014] Preferably, the molar ratio of the amino group in the amino acid to the aldehyde group in the aldehyde is (0.5-2):1.

[0015] Preferably, the reaction temperature in step B) is 110-160° C., and the reaction time in step B) is 0.5-5 hours.

[0016] The present invention provides an amino acid-based adhesive, which is prepared according to the preparation method described above.

[0017] The present invention provides use of the amino acid-based adhesive as described above in plywood.

[0018] The present invention provides a method for preparing an amino acid-based adhesive, comprising the following steps: A) mixing an organic small molecule superbase with an aldehyde, heating and stirring, to obtain a deep eutectic solvent; the organic small molecule superbase comprises 1,8-diazabicyclo[5.4.0]undec-7-ene and / or 1,5-diazabicyclo[4.3.0]non-5-ene; and the aldehyde comprises one or more of vanillin, cinnamaldehyde, and furfural; and B) mixing the deep eutectic solvent with an amino acid, heating and reacting, to obtain an amino acid-based adhesive.

[0019] Compared with the existing technology, the beneficial effects of the present invention are:

[0020] (1) Use greener low eutectic solvents to replace organic solvents.

[0021] (2) Use some low-toxic aldehydes such as vanillin / cinnamaldehyde / furfural that are non-toxic and harmless from plants to replace toxic and harmful formaldehyde.

[0022] (3) Use more readily available amino acids instead of urea.

[0023] (4) Compared with traditional urea-formaldehyde resin, the amino acid-based adhesive produced by this method has higher bonding strength, providing a reliable way to prepare green and safe plywood.

[0024] (5) The one-pot method is used, which simplifies the preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0026] Figure 1The shear test results of the adhesives prepared in Examples 1, 4, 7, 10, 13, 16 and 19 of the present invention are shown;

[0027] Figure 2 This is the shear surface condition of the adhesive of Example 4 after the bonding strength test;

[0028] Figure 3 This is the shear test result of the adhesive in Example 23 of the present invention;

[0029] Figure 4 This is the shear test result of the adhesive in Example 24 of the present invention;

[0030] Figure 5 The state of the mixed solution prepared in step 1) of Comparative Example 1;

[0031] Figure 6 for Figure 5 The state of the mixed solution after cooling;

[0032] Figure 7 This is the state of the mixed solution prepared in Comparative Example 3;

[0033] Figure 8 This is the state of the mixed solution prepared in Comparative Example 4;

[0034] Figure 9 is the bonding strength of the adhesive in Comparative Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0035] The present invention provides a method for preparing an amino acid-based adhesive, comprising the following steps:

[0036] A) mixing an organic small molecule superbase with an aldehyde, heating and stirring, to obtain a deep eutectic solvent;

[0037] The organic small molecule superbase includes 1,8-diazabicyclo[5.4.0]undec-7-ene and / or 1,5-diazabicyclo[4.3.0]non-5-ene;

[0038] The aldehyde includes one or more of vanillin, cinnamaldehyde and furfural;

[0039] B) mixing a deep eutectic solvent with an amino acid, and heating the mixture to react to obtain an amino acid-based adhesive.

[0040] The present invention first forms a stable low eutectic solvent with an organic small molecule superbase and an aldehyde, and then mixes it with an amino acid, so that the aldehyde in the aldehyde reacts based on the amino group in the amino acid to prepare an adhesive. This can not only improve the bonding strength of the adhesive, but also improve the stability of the adhesive and expand the types of raw amino acids.

[0041] In the present invention, the organic small molecule superbase preferably includes 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and / or 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), and the aldehyde preferably includes one or more of vanillin, cinnamaldehyde and furfural; the molar ratio of the aldehyde to the organic small molecule superbase is preferably (0.5-2):1, more preferably (0.8-1.5):1, such as 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, preferably a range value with any of the above values ​​as the upper or lower limit.

[0042] The present invention preferably heats and stirs the mixture of the organic small molecule superbase and the aldehyde under oil bath conditions, and the heating and stirring temperature is preferably 70-120°C, more preferably 80-110°C, such as 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, preferably with any of the above values ​​as the upper or lower limit of the range value; the heating and stirring time is preferably 15-40 min, more preferably 20-35 min.

[0043] The deep eutectic solvent (DES) obtained by the present invention is in a clear and transparent state, and no crystals are precipitated after being cooled to room temperature.

[0044] After obtaining the deep eutectic solvent, the present invention mixes the deep eutectic solvent with an amino acid, raises the temperature, and reacts under stirring to obtain an amino acid-based adhesive.

[0045] In the present invention, the amino acids preferably include one or more of tryptophan, lysine, phenylalanine, methionine, threonine, valine, leucine, isoleucine, cysteine, serine, glycine, tyrosine, aspartic acid, asparagine, glutamic acid, glutamine, alanine, arginine, histidine and proline; the molar ratio of the amino group in the amino acid to the aldehyde group in the aldehyde is preferably (0.5-2):1, more preferably (0.8-1.5):1, such as 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, preferably a range value with any of the above values ​​as the upper or lower limit.

[0046] In the present invention, the reaction temperature is preferably 110-160°C, more preferably 120-150°C, such as 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, preferably a range value with any of the above values ​​as the upper or lower limit; the reaction time is preferably 0.5-5 hours, more preferably 1-4 hours.

[0047] The present invention also provides an amino acid-based adhesive, which is prepared according to the preparation method described above.

[0048] The present invention also provides use of the amino acid-based adhesive described above in bonding board materials, such as plywood.

[0049] The present invention provides a method for preparing an amino acid-based adhesive, comprising the following steps: A) mixing an organic small molecule superbase with an aldehyde, heating and stirring, to obtain a deep eutectic solvent; the organic small molecule superbase comprises 1,8-diazabicyclo[5.4.0]undec-7-ene and / or 1,5-diazabicyclo[4.3.0]non-5-ene; and the aldehyde comprises one or more of vanillin, cinnamaldehyde, and furfural; and B) mixing the deep eutectic solvent with an amino acid, heating and reacting, to obtain an amino acid-based adhesive.

[0050] Compared with the existing technology, the beneficial effects of the present invention are:

[0051] (1) Use greener low eutectic solvents to replace organic solvents.

[0052] (2) Use some low-toxic aldehydes such as vanillin / cinnamaldehyde / furfural that are non-toxic and harmless from plants to replace toxic and harmful formaldehyde.

[0053] (3) Use more readily available amino acids instead of urea.

[0054] (4) Compared with traditional urea-formaldehyde resin, the amino acid-based adhesive produced by this method has higher bonding strength, providing a reliable way to prepare green and safe plywood.

[0055] (5) The one-pot method is used, which simplifies the preparation process.

[0056] To further illustrate the present invention, an amino acid-based adhesive, its preparation method and application provided by the present invention are described in detail below with reference to the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0057] Example 1

[0058] 1) Weigh 4 g of vanillin and 4 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) into a flask, place it in a 90°C oil bath, and heat with stirring for 15 minutes to obtain a clear and transparent deep eutectic solvent (DES).

[0059] 2) Weigh 4.07 g of L-histidine and add it to the prepared deep eutectic solvent (DES). Raise the temperature to 130°C.

[0060] 3) After the reaction time reaches 1 hour, the adhesive is poured out from the flask to obtain a histidine composite adhesive having a molar ratio of amino groups to aldehyde groups of 1:1.

[0061] Example 2

[0062] A composite adhesive was prepared according to the method of Example 1, except that 4.07 g of L-histidine in step 2) of Example 1 was replaced with 2.04 g of L-histidine to prepare a histidine composite adhesive with a molar ratio of amino groups to aldehyde groups of 0.5:1.

[0063] Example 3

[0064] A composite adhesive was prepared according to the method of Example 1, except that 4.07 g of L-histidine in step 2) of Example 1 was replaced with 6.11 g of L-histidine to prepare a histidine composite adhesive with a molar ratio of amino groups to aldehyde groups of 1.5:1.

[0065] Example 4

[0066] 1) Weigh 4 g of vanillin and 4 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) into a flask, place it in a 90°C oil bath, and heat with stirring for 15 minutes to obtain a clear and transparent deep eutectic solvent (DES).

[0067] 2) Weigh 3.86 g of L-glutamic acid and add it to the prepared deep eutectic solvent (DES), and raise the temperature to 130°C.

[0068] 3) After the reaction time reaches 1 hour, the adhesive is poured out from the flask to obtain a glutamic acid composite adhesive having a molar ratio of amino groups to aldehyde groups of 1:1.

[0069] Example 5

[0070] A composite adhesive was prepared according to the method of Example 4, except that 3.86 g of L-glutamic acid in step 2) of Example 4 was replaced with 1.93 g of L-glutamic acid to prepare a glutamic acid composite adhesive with a molar ratio of amino groups to aldehyde groups of 0.5:1.

[0071] Example 6

[0072] A composite adhesive was prepared according to the method of Example 4, except that 3.86 g of L-glutamic acid in step 2) of Example 4 was replaced with 5.79 g of glutamic acid to prepare a glutamic acid composite adhesive with a molar ratio of amino groups to aldehyde groups of 1.5:1.

[0073] Example 7

[0074] 1) Weigh 4 g of vanillin and 4 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) into a flask, place it in a 90°C oil bath, and heat with stirring for 15 minutes to obtain a clear and transparent deep eutectic solvent (DES).

[0075] 2) Weigh 3.50 g of L-aspartic acid and add it to the prepared deep eutectic solvent (DES). Raise the temperature to 130°C.

[0076] 3) After the reaction time reaches 1 hour, the adhesive is poured out of the flask to obtain an aspartic acid composite adhesive having a molar ratio of amino groups to aldehyde groups of 1:1.

[0077] Example 8

[0078] A composite adhesive was prepared according to the method of Example 7, except that 3.50 g of L-aspartic acid in step 2) of Example 7 was replaced with 1.75 g of L-aspartic acid to prepare an aspartic acid composite adhesive with a molar ratio of amino groups to aldehyde groups of 0.5:1.

[0079] Example 9

[0080] A composite adhesive was prepared according to the method of Example 7, except that 3.50 g of L-aspartic acid in step 2) of Example 7 was replaced with 5.75 g of L-aspartic acid to prepare an aspartic acid composite adhesive with a molar ratio of amino groups to aldehyde groups of 1.5:1.

[0081] Example 10

[0082] 1) Weigh 4 g of vanillin and 4 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) into a flask, place it in a 90°C oil bath, and heat with stirring for 15 minutes to obtain a clear and transparent deep eutectic solvent (DES).

[0083] 2) Weigh 4.34 g of L-phenylalanine and add it to the prepared deep eutectic solvent (DES). Raise the temperature to 130°C.

[0084] 3) After the reaction time reaches 1 hour, the adhesive is poured out from the flask to obtain a phenylalanine composite adhesive having a molar ratio of amino groups to aldehyde groups of 1:1.

[0085] Example 11

[0086] A composite adhesive was prepared according to the method of Example 10, except that 4.34 g of L-phenylalanine in step 2) of Example 10 was replaced with 2.17 g of L-phenylalanine to prepare a phenylalanine composite adhesive with a molar ratio of amino groups to aldehyde groups of 0.5:1.

[0087] Example 12

[0088] A composite adhesive was prepared according to the method of Example 10, except that 4.34 g of L-phenylalanine in step 2) of Example 10 was replaced with 6.51 g of L-phenylalanine to prepare a phenylalanine composite adhesive with a molar ratio of amino groups to aldehyde groups of 1.5:1.

[0089] Example 13

[0090] 1) Weigh 4 g of vanillin and 4 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) into a flask, place it in a 90°C oil bath, and heat with stirring for 15 minutes to obtain a clear and transparent deep eutectic solvent (DES).

[0091] 2) Weigh 1.97 g of glycine and add it to the prepared deep eutectic solvent (DES), and raise the temperature to 130°C.

[0092] 3) After the reaction time reaches 1 hour, the adhesive is poured out from the flask to obtain a glycine composite adhesive having a molar ratio of amino groups to aldehyde groups of 1:1.

[0093] Example 14

[0094] A composite adhesive was prepared according to the method of Example 13, except that 1.97 g of glycine in step 2) of Example 13 was replaced with 0.99 g of glycine to prepare a glycine composite adhesive with a molar ratio of amino groups to aldehyde groups of 0.5:1.

[0095] Example 15

[0096] A composite adhesive was prepared according to the method of Example 13, except that 1.97 g of glycine in step 2) of Example 13 was replaced with 2.96 g of glycine to prepare a glycine composite adhesive with a molar ratio of amino groups to aldehyde groups of 1.5:1.

[0097] Example 16

[0098] 1) Weigh 4 g of vanillin and 4 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) into a flask, place it in a 90°C oil bath, and heat with stirring for 15 minutes to obtain a clear and transparent deep eutectic solvent (DES).

[0099] 2) Weigh 2.34 g of L-alanine and add it to the prepared deep eutectic solvent (DES), and raise the temperature to 130°C.

[0100] 3) After the reaction time reaches 1 hour, the adhesive is poured out from the flask to obtain an alanine composite adhesive having a molar ratio of amino groups to aldehyde groups of 1:1.

[0101] Example 17

[0102] A composite adhesive was prepared according to the method in Example 16, except that 2.34 g of L-alanine in step 2) of Example 16 was replaced with 1.17 g of L-alanine to prepare an alanine composite adhesive with a molar ratio of amino groups to aldehyde groups of 0.5:1.

[0103] Example 18

[0104] A composite adhesive was prepared according to the method of Example 16, except that 2.34 g of L-alanine in step 2) of Example 16 was replaced with 3.51 g of L-alanine to prepare an alanine composite adhesive with a molar ratio of amino groups to aldehyde groups of 1.5:1.

[0105] Example 19

[0106] 1) Weigh 4 g of vanillin and 4 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) into a flask, place it in a 90°C oil bath, and heat with stirring for 15 minutes to obtain a clear and transparent deep eutectic solvent (DES).

[0107] 2) Weigh 3.13 g of L-threonine and add it to the prepared deep eutectic solvent (DES), and raise the temperature to 130°C.

[0108] 3) After the reaction time reaches 1 hour, the adhesive is poured out from the flask to obtain a threonine composite adhesive having a molar ratio of amino groups to aldehyde groups of 1:1.

[0109] Example 20

[0110] A composite adhesive was prepared according to the method of Example 19, except that 3.13 g of L-threonine in step 2) of Example 19 was replaced with 1.57 g of L-threonine to prepare a threonine composite adhesive with a molar ratio of amino group to aldehyde group of 0.5:1.

[0111] Example 21

[0112] A composite adhesive was prepared according to the method in Example 19, except that 3.13 g of L-threonine in step 2) of Example 19 was replaced with 4.70 g of L-threonine to prepare a threonine composite adhesive with a molar ratio of amino group to aldehyde group of 1.5:1.

[0113] Example 22

[0114] An amino acid composite adhesive was prepared according to the preparation method in Example 1, except that the L-histidine in Example 1 was replaced by tryptophan, lysine, methionine, valine, leucine, isoleucine, cysteine, serine, tyrosine, asparagine, glutamine, arginine and proline containing the same molar amino groups.

[0115] Example 23

[0116] An amino acid composite adhesive was prepared according to the preparation method in Example 1, except that the DBU in Example 1 was replaced with an equal molar amount of DBN.

[0117] Example 24

[0118] The vanillin in Example 1 was replaced with cinnamaldehyde and furfural in equal moles, and different amino acid adhesives were prepared using the same method as in Examples 1 to 8.

[0119] Comparative Example 1

[0120] 1) Weigh 4 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) into a flask, weigh 4.07 g of L-histidine, add the mixture to the flask, and place the flask in an oil bath at 130°C to obtain a mixed solution;

[0121] 2) Weigh 4 g of vanillin and add it to the mixed solution prepared in 1).

[0122] 3) After the reaction has proceeded for 1 hour, the adhesive was poured out of the flask to obtain a histidine composite adhesive comparative sample 1 having a molar ratio of amino groups to aldehyde groups of 1:1.

[0123] Comparative Example 2

[0124] 1) Weigh 4 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in a flask, weigh 4.07 g of L-histidine, add the mixture to the flask, and place it in an oil bath at 130°C to obtain a mixed solution.

[0125] 2) Weigh 4 g of vanillin and add it to the mixed solution prepared in 1).

[0126] 3) After the reaction has proceeded for 2 hours, the adhesive was poured out of the flask to obtain a histidine composite adhesive comparative sample 2 having a molar ratio of amino groups to aldehyde groups of 1:1.

[0127] Comparative Example 3

[0128] 4 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was weighed into a flask, and 3.50 g of L-aspartic acid was weighed and added to the flask, which was then placed in an oil bath at 130° C. to obtain a mixed solution.

[0129] Comparative Example 4

[0130] 4 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was weighed into a flask, and 1.97 g of glycine was added to the flask. The flask was then placed in an oil bath at 130°C to obtain a mixed solution. Observation revealed that the solution was also insoluble.

[0131] Performance Testing

[0132] Experimental methods

[0133] Adhesion strength is the most important metric for evaluating adhesives. To test the adhesive's effectiveness, the adhesive prepared in this invention was tested according to GB / T 33333-2016, Adhesives—Determination of Tensile Shear Strength. The prepared adhesive was applied to a 60 mm × 20 mm × 3 mm wooden surface at room temperature, covering an area of ​​20 mm × 20 mm. The hot press was applied at a pressure of 0.13 MPa. Each sample was repeated five times to confirm the reproducibility of the bond strength data.

[0134] Experimental results

[0135] The shear test results of Example 1, Example 4, Example 7, Example 10, Example 13, Example 16 and Example 19 are as follows: Figure 1 The bonding strength of histidine reached 4.82 MPa, followed by aspartic acid and glutamic acid, at 4.22 MPa and 4.12 MPa, respectively. These strengths are far higher than the national bond strength requirement for wood adhesives (≥0.7 MPa) in GB / T 14732-2017. The bonding strengths of the other four amino acids all exceeded 3 MPa. This indicates that the addition of different amino acids will result in higher bonding strengths for the adhesives in this system.

[0136] Example 23 Shearing results are as follows Figure 3 As shown in the figure, the strongest bonding strength of the amino acid-based adhesive prepared by using DBN instead of DBU is 2.5 MPa, which is less than the maximum bonding strength of the adhesive prepared by DBU (4.82 MPa). However, the adhesive prepared by DBN still has a bonding strength that exceeds the requirement of GB / T 14732-2017 (≥0.7 MPa). This shows that DBN can also be used as one of the raw materials, but its strength is weaker than that of DBU.

[0137] Example 24 Shearing results are as follows Figure 4As shown in the figure, the strongest bonding strength of the amino acid-based adhesive prepared with cinnamaldehyde instead of vanillin is 2.2 MPa, and the strongest bonding strength of the amino acid-based adhesive prepared with furfural instead of vanillin is 2.54 MPa, both of which are less than the maximum bonding strength of the adhesive prepared with vanillin, 4.82 MPa. However, the adhesives prepared with these two aldehydes still have a bonding strength that exceeds the requirement of GB / T 14732-2017 (≥0.7 MPa). This shows that cinnamaldehyde, furfural and other low-toxic aldehydes can also be used as one of the raw materials, but their strength is weaker than that of vanillin.

[0138] The mixed solution prepared in Comparative Example 1 was as follows Figures 5 and 6 As shown, Figure 5 The state of the mixed solution prepared in step 1) of Comparative Example 1 is as follows: Figure 6 for Figure 5 The state of the mixed solution after cooling is determined by Figures 5-6 It can be seen that the mixed solution of DBU and L-histidine is turbid, and after cooling, it is found that L-histidine is completely precipitated, which does not meet the characteristics of a low eutectic solvent, so the two cannot form a low eutectic solvent.

[0139] Figure 7 The state of the mixed solution prepared in Comparative Example 3 is Figure 7 It can be seen that DBU and L-aspartic acid are not miscible and are in a phase-separated state.

[0140] Figure 8 The state of the mixed solution prepared in Comparative Example 4 is Figure 8 It can be seen that DBU and glycine are also insoluble.

[0141] Depend on Figure 9 It can be seen that the adhesive can still be generated by first mixing the organic small molecule superbase with the amino acid and then adding the aldehyde, but the bonding strength of the adhesive prepared by this method is much lower than the bonding strength of the adhesive prepared by the method in the embodiment of the present invention, which is 4.82 MPa. This also proves that the adhesive prepared by the method of the present invention does not have a higher bonding strength.

[0142] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing an amino acid-based adhesive, comprising the following steps: A) mixing an organic small molecule superbase with an aldehyde, heating and stirring, to obtain a deep eutectic solvent; The organic small molecule superbase includes 1,8-diazabicyclo[5.4.0]undec-7-ene and / or 1,5-diazabicyclo[4.3.0]non-5-ene; The aldehyde includes one or more of vanillin, cinnamaldehyde and furfural; B) mixing a deep eutectic solvent with an amino acid, and heating the mixture to react to obtain an amino acid-based adhesive.

2. The method for preparing the amino acid-based adhesive according to claim 1, wherein In the step A), the molar ratio of aldehyde to organic small molecule superbase is (0.5-2):

1.

3. The method for preparing the amino acid-based adhesive according to claim 1, wherein: The temperature for heating and stirring in step A) is 70-120° C., and the time for heating and stirring in step A) is 15-40 minutes.

4. The method for preparing the amino acid-based adhesive according to claim 3, wherein: The reaction in step A) is carried out under dry conditions.

5. The method for preparing the amino acid-based adhesive according to claim 1, wherein: The deep eutectic solvent obtained in step A) is in a clear and transparent state, and no crystals are precipitated after cooling to room temperature.

6. The method for preparing the amino acid-based adhesive according to claim 1, wherein: The amino acids in step B) include one or more of tryptophan, lysine, phenylalanine, methionine, threonine, valine, leucine, isoleucine, cysteine, serine, glycine, tyrosine, aspartic acid, asparagine, glutamic acid, glutamine, alanine, arginine, histidine and proline.

7. The method for preparing the amino acid-based adhesive according to claim 1, wherein: The molar ratio of the amino group in the amino acid to the aldehyde group in the aldehyde is (0.5-2):

1.

8. The method for preparing an amino acid-based adhesive according to claim 1, wherein: The reaction temperature in step B) is 110-160° C., and the reaction time in step B) is 0.5-5 hours.

9. An amino acid-based adhesive prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the amino acid-based adhesive according to claim 9 in plywood.

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