Polyglutamic acid / epoxidized soybean oil-based adhesive and preparation method thereof

Abstract

The invention provides a polyglutamic acid / epoxidized soybean oil-based adhesive and a preparation method thereof. The polyglutamic acid / epoxidized soybean oil-based adhesive is prepared from the following raw materials in parts by weight: 10-65 parts of polyglutamic acid, 20-50 parts of epoxidized soybean oil and 0-30 parts of tannic acid. The relative molecular weight of the polyglutamic acid is 100000-2000000 g / mol, the polyglutamic acid comprises a glutamic acid unit and a sodium glutamate unit, and the mass percentage of the glutamic acid unit is 30-60%. The adhesive is prepared from polyglutamic acid, epoxidized soybean oil and tannic acid which are all biological sources. According to the prepared polyglutamic acid / epoxidized soybean oil-based epoxy resin adhesive, the reaction between an epoxy group and a polycarboxyl group is utilized, meanwhile, tannic acid is used for increasing, bisphenol A which is toxic and harmful to a human body is not used, the bonding strength can reach 10 MPa, and the polyglutamic acid / epoxidized soybean oil-based epoxy resin adhesive can be applied to multiple application scenes such as multiple wood and steel adhesives.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesives, and in particular relates to a polyglutamic acid / epoxidized soybean oil-based adhesive and a preparation method thereof. Background Art

[0002] Commercial adhesives currently used in the fields of wood and other fields often contain toxic gases such as formaldehyde, which are harmful to human health. It is necessary to develop a VOC-free environmentally friendly adhesive. At the same time, the current commercial adhesives are often not fully biodegradable after use, and a large amount of polymer waste is generated, which affects the ecological environment. It is necessary to develop a fully bio-based and biodegradable adhesive. However, the current biomass raw materials are often costly, and it is necessary to select biomass raw materials that can be mass-produced to prepare cheap bio-based cross-linking agents. Epoxy resin is a widely used adhesive, but the currently used epoxy resin is mainly prepared by the reaction of epoxy groups and bisphenol A, and the harm of bisphenol A to the human body includes endocrine system disruption, reproductive system effects, increased cancer risk, etc., so it is necessary to develop a more environmentally friendly epoxy resin adhesive. Summary of the invention

[0003] The object of the present invention is to provide a polyglutamic acid / epoxidized soybean oil-based adhesive and a preparation method thereof. The polyglutamic acid / epoxidized soybean oil-based adhesive of the present invention does not use bisphenol A which is toxic to the human body, and is beneficial to human health. The adhesive provided by the present invention has a bonding strength of up to 10 MPa, and can be used in a variety of application scenarios such as a variety of wood and steel adhesives.

[0004] The present invention provides a polyglutamic acid / epoxidized soybean oil-based adhesive, comprising the following raw materials in parts by weight:

[0005] Polyglutamic acid: 10-65 parts, epoxidized soybean oil: 20-50 parts, tannic acid: 0-30 parts;

[0006] The relative molecular weight of the polyglutamic acid is 100000-2000000 g / mol. The polyglutamic acid comprises glutamic acid units and sodium glutamate units, and the mass percentage of the glutamic acid units is 30-60%.

[0007] Preferably, the epoxidation value of the epoxidized soybean oil is greater than 0.6 mol / 100 g.

[0008] Preferably, the mass percentage of the glutamic acid unit is 40-60%.

[0009] Preferably, the weight proportion of polyglutamic acid is 30 to 65 parts.

[0010] Preferably, the weight proportion of tannic acid is 0 to 20 parts.

[0011] Preferably, the molar ratio of the carboxyl groups in the polyglutamic acid to the epoxy groups in the epoxidized soybean oil is 1:(0.9-1.1).

[0012] The present invention provides a method for preparing the polyglutamic acid / epoxidized soybean oil-based adhesive as described above, comprising the following steps:

[0013] A) mixing polyglutamic acid, epoxidized soybean oil and tannic acid to form a prepolymer;

[0014] B) coating the prepolymer on the surface of the material to be bonded and curing the prepolymer to obtain a cured polyglutamic acid / epoxidized soybean oil-based adhesive.

[0015] Preferably, the mixing temperature in step A) is 60-100° C., and the mixing time in step A) is 1-24 hours.

[0016] Preferably, the curing temperature in step B) is 150-180° C., and the curing time in step B) is 1-8 hours.

[0017] The present invention provides a polyglutamic acid / epoxidized soybean oil-based adhesive, comprising the following raw materials in parts by weight: polyglutamic acid: 10-65 parts, epoxy soybean oil: 20-50 parts, tannic acid: 0-30 parts; the relative molecular weight of the polyglutamic acid is 100000-2000000 g / mol, the polyglutamic acid includes glutamic acid units and sodium glutamate units, and the mass percentage of the glutamic acid units is 30-60%. The polyglutamic acid / epoxidized soybean oil-based adhesive prepared by the present invention is prepared from polyglutamic acid, epoxy soybean oil, and tannic acid of all biological sources. The polyglutamic acid / epoxidized soybean oil-based epoxy resin adhesive prepared by the present invention utilizes the reaction between epoxy groups and polycarboxyl groups, and uses tannic acid to increase the strength, and does not use bisphenol A which is toxic to the human body, which is beneficial to human health. The adhesive provided by the present invention has a bonding strength of up to 10MPa, and can be used in multiple application scenarios such as a variety of wood and steel adhesives. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0019] Figure 1 This is a picture of the prepolymer of the polyglutamic acid / epoxidized soybean oil-based / tannic acid adhesive in Example 1 of the present invention;

[0020] Figure 2This is the original shear strength curve of five parallel samples of the adhesive in Example 1 of the present invention bonded to steel sheets and tested using a tensile testing machine after curing. DETAILED DESCRIPTION

[0021] The present invention provides a polyglutamic acid / epoxidized soybean oil-based adhesive, comprising the following raw materials in parts by weight:

[0022] Polyglutamic acid: 10-65 parts, epoxidized soybean oil: 20-50 parts, tannic acid: 0-30 parts;

[0023] The relative molecular weight of the polyglutamic acid is 100000-2000000 g / mol. The polyglutamic acid comprises glutamic acid units and sodium glutamate units, and the mass percentage of the glutamic acid units is 30-60%.

[0024] In the present invention, the weight proportion of the polyglutamic acid is preferably 10 to 65 parts, more preferably 15 to 60 parts, such as 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, preferably a range value with any of the above values ​​as the upper or lower limit.

[0025] In the present invention, the weight proportion of the epoxidized soybean oil is preferably 20 to 50 parts, more preferably 25 to 45 parts, such as 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, preferably a range value with any of the above values ​​as the upper or lower limit.

[0026] In the present invention, the weight proportion of the tannic acid is preferably 0-30 parts, more preferably 5-25 parts, such as 0 parts, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, preferably a range value with any of the above values ​​as the upper or lower limit.

[0027] When the total weight parts of the polyglutamic acid, epoxy soybean oil and tannic acid is 100 weight parts, the weight parts of the polyglutamic acid, epoxy soybean oil and tannic acid mentioned above may be equivalent to the mass percentage.

[0028] In the present invention, when the mass fraction of the polyglutamic acid content in the adhesive is lower than 10 wt%, the carboxyl functional group content in the adhesive is low, which affects the bonding strength of the adhesive. When the mass fraction of the polyglutamic acid content in the adhesive is higher than 50 wt%, due to the high viscosity of the polyglutamic acid itself, the viscosity of the prepolymer formed is very large, and it is not easy to flow, which affects the coating of the adhesive. The epoxy groups in the epoxy soybean oil in the present invention react with the carboxyl groups in the polyglutamic acid to form crosslinking points. In order to effectively form a crosslinking reaction, the molar ratio of the carboxyl groups in the polyglutamic acid and the epoxy groups in the epoxy soybean oil is controlled to be about 1:1, so the mass fraction of the epoxy soybean oil in the present invention is related to the carboxyl content in the added polyglutamic acid. Tannic acid contains multiple phenolic hydroxyl groups, which can be self-oxidized and cross-linked to form a crosslinked network structure, and is used to increase the bonding strength of the adhesive in the present invention. However, when the content of tannic acid in the polyglutamic acid / epoxy soybean oil base / tannic acid exceeds 30 wt%, the fracture strain of the cured adhesive is small, thereby affecting the bonding performance.

[0029] In the present invention, the relative molecular weight of the polyglutamic acid is preferably 100000-2000000 g / mol, more preferably 200000~1000000 g / mol, and the polyglutamic acid includes glutamic acid units and sodium glutamate units, wherein the mass percentage of the glutamic acid units is preferably 30~60%, more preferably 40~60%, such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, preferably a range value with any of the above values ​​as the upper or lower limit.

[0030] In the present invention, when the molecular weight of polyglutamic acid is lower than 100000 g / mol, the shear strength is low due to the small physical entanglement of polyglutamic acid itself. When the molecular weight of polyglutamic acid in the present invention is higher than 2000000 g / mol, the viscosity of polyglutamic acid itself is very high, and it is difficult to stir in the prepolymerization stage, and it is difficult to form a uniform reaction system.

[0031] Commercial polyglutamic acid usually contains glutamic acid units and sodium glutamate units. In the present invention, the molar percentage of glutamic acid units and sodium glutamate units in polyglutamic acid can be calculated by measuring the sodium content in polyglutamic acid with a conventional plasma emission spectrometer. The specific calculation is as follows: Assuming that the sodium content in polyglutamic acid measured by the plasma emission spectrometer is m1 (ppm), according to the molar masses of sodium, glutamic acid units, and sodium glutamate units are 23 g / mol, 129 g / mol, and 151 g / mol, respectively, the formula for calculating the molar percentage (F) of glutamic acid units in polyglutamic acid is:

[0032] (1)

[0033] In the present invention, when the proportion of glutamic acid units in polyglutamic acid is less than 30%, the adhesive has poor bonding properties due to the low content of reactive carboxyl groups on each polyglutamic acid side chain. When the proportion of glutamic acid units in polyglutamic acid is higher than 60%, a large number of carboxyl groups react with epoxy groups in the prepolymer formation stage to form a non-sticky block material, which is not conducive to coating during the later curing.

[0034] In the present invention, the epoxy value of the epoxidized soybean oil is preferably greater than 0.6 mol / 100 g. Generally, the maximum epoxy value of commercial epoxidized soybean oil is 0.616 mol / 100 g. In order to control the content of epoxy groups per unit mass of epoxidized soybean oil in the present invention to improve the bonding performance of the adhesive, the epoxy value of the epoxidized soybean oil used is required to be greater than 0.6 mol / 100 g.

[0035] The present invention also provides a method for preparing a polyglutamic acid / epoxidized soybean oil-based adhesive, comprising the following steps:

[0036] A) mixing polyglutamic acid, epoxidized soybean oil and tannic acid to form a prepolymer;

[0037] B) coating the prepolymer on the surface of the material to be bonded and curing the prepolymer to obtain a cured polyglutamic acid / epoxidized soybean oil-based adhesive.

[0038] In the present invention, the physical parameters and dosage of the polyglutamic acid, epoxy soybean oil and tannic acid are consistent with the physical parameters and dosage of the polyglutamic acid, epoxy soybean oil and tannic acid described above, and the present invention will not be repeated here.

[0039] In the present invention, the temperature for mixing to form a prepolymer is preferably carried out at a relatively low temperature, preferably 60 to 100°C, more preferably 70 to 90°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, preferably a range value with any of the above values ​​as the upper or lower limit; the time for mixing to form a prepolymer is preferably 1 to 24 hours, more preferably 5 to 20 hours.

[0040] In the present invention, when the prepolymer reaction temperature is lower than 60°C and the prepolymer reaction time is greater than 24 h, the production efficiency is affected. At lower temperatures such as room temperature, the reaction degree is very low, and the glue is easy to flow and difficult to apply. In the present invention, when the prepolymer reaction temperature is higher than 100°C, the prepolymer reaction time can be less than 1h. If the prepolymer reaction temperature is higher, the reaction speed is very fast, the reaction degree is difficult to control, and a non-sticky solid is easily formed. When the prepolymer reaction temperature is 100°C and the prepolymer reaction time can be greater than 1 h, the reaction degree in the prepolymer stage is too high and it is not easy to apply.

[0041] In the present invention, the curing reaction is preferably carried out at a relatively high temperature, preferably 150-180°C, more preferably 160-170°C, such as 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, preferably a range value with any of the above values ​​as the upper or lower limit; the curing reaction time is preferably 1-8 hours, more preferably 3-5 hours.

[0042] In the present invention, when the curing temperature is lower than 150°C and the prepolymer reaction time is greater than 8 hours, the production efficiency is affected. In the present invention, when the prepolymer reaction temperature is higher than 180°C, the curing reaction time can be less than 1 hour. If the curing temperature is higher, it may cause high-temperature decomposition of the adhesive, affecting the bonding performance. When the prepolymer reaction temperature is 180°C and the curing reaction time can be greater than 1 hour, it is also easy to cause transitional crosslinking, and the fracture strain of the formed adhesive is small.

[0043] The present invention provides a polyglutamic acid / epoxidized soybean oil-based adhesive, comprising the following raw materials in parts by weight: polyglutamic acid: 10-65 parts, epoxy soybean oil: 20-50 parts, tannic acid: 0-30 parts; the relative molecular weight of the polyglutamic acid is 100000-2000000 g / mol, the polyglutamic acid includes glutamic acid units and sodium glutamate units, and the mass percentage of the glutamic acid units is 30-60%. The polyglutamic acid / epoxidized soybean oil-based adhesive prepared by the present invention is prepared from polyglutamic acid, epoxy soybean oil, and tannic acid of all biological sources. The polyglutamic acid / epoxidized soybean oil-based epoxy resin adhesive prepared by the present invention utilizes the reaction between epoxy groups and polycarboxyl groups, and uses tannic acid to increase the strength, and does not use bisphenol A which is toxic to the human body, which is beneficial to human health. The adhesive provided by the present invention has a bonding strength of up to 10MPa, and can be used in multiple application scenarios such as a variety of wood and steel adhesives.

[0044] In order to further illustrate the present invention, a polyglutamic acid / epoxidized soybean oil-based adhesive and a preparation method thereof provided by the present invention are described in detail below in conjunction with examples, but it should not be construed as limiting the scope of protection of the present invention.

[0045] Example 1

[0046] Formula components: 59.2 parts of polyglutamic acid with a glutamic acid unit ratio of 40% and a molecular weight of 100,000 g / mol, 27 parts of epoxidized soybean oil, and 13.8 parts of tannic acid.

[0047] The mass ratio of polyglutamic acid and epoxidized soybean oil is calculated as follows: Based on the molar masses of glutamic acid unit and sodium glutamate unit of 129 g / mol and 151 g / mol respectively, the average molecular weight of the repeating unit in polyglutamic acid with glutamic acid unit accounting for 40% is: 129 × 40% + 151 × 60% = 142.3 g / mol. Assuming that there is 10 g of epoxidized soybean oil with an epoxy value of 0.616 mol / 100g (molecular weight is 974 g / mol), the mass m2 of polyglutamic acid with equivalent carboxyl content that has reacted with all epoxy groups is calculated as follows:

[0048] (10 × 6) / 974 = (m2 / 142.3) × 40%

[0049] The calculated value of m2 = 21.9 g indicates that the mass ratio of polyglutamic acid to epoxidized soybean oil is 2.19:1. In the following embodiments and comparative examples, if the molar ratio of the carboxyl group in the designed polyglutamic acid to the epoxy group in the epoxidized soybean oil is also 1:1, the mass ratio is calculated in the same manner as above.

[0050] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 70°C for 6 hours to form a prepolymer, such as Figure 1 shown.

[0051] Steel sheet bonding experiment: 5 pairs of stainless steel sheets with a length of 10 cm and a width of 1 cm were butt-jointed with prepolymer coating. The coating bonding area was 1 × 1 cm 2 After fixing the bonding part with a dovetail clip, place it in a 180℃ temperature to cure for 1 hour. Then cool it naturally at room temperature.

[0052] Adhesive shear strength test: The five pairs of steel sheets cured with the adhesive were tested by a tensile machine to obtain the curves of load (N) versus mechanical elongation (mm), as shown in Figure 2. Figure 2 As shown. The bonding strength (MPa) was obtained by dividing the maximum load by the bonding area. The average bonding strength of the five samples was 2.13 MPa.

[0053] Example 2

[0054] Formula components: 53.5 parts of polyglutamic acid with a glutamic acid unit ratio of 50% and a molecular weight of 1000000 g / mol, 31.1 parts of epoxidized soybean oil, and 15.4 parts of tannic acid.

[0055] The mass ratio of polyglutamic acid and epoxidized soybean oil is calculated as follows: Based on the molar masses of glutamic acid unit and sodium glutamate unit of 129 g / mol and 151 g / mol respectively, the average molecular weight of the repeating unit in polyglutamic acid with glutamic acid unit accounting for 50% is: 129 × 50% + 151 × 50% = 140 g / mol. Assuming that there is 10 g of epoxidized soybean oil with an epoxy value of 0.616 mol / 100g (molecular weight is 974 g / mol), the mass m2 of polyglutamic acid with equivalent carboxyl content that has reacted with all epoxy groups is calculated as follows:

[0056] (10 × 6) / 974 = (m2 / 140) × 50%

[0057] The calculated m2 = 17.2 g, that is, the mass ratio of polyglutamic acid to epoxidized soybean oil is 1.72:1. In the following examples and comparative examples, if the molar ratio of the carboxyl group in the designed polyglutamic acid to the epoxy group in the epoxidized soybean oil is also 1:1, the mass ratio is calculated in the same way as above. The following examples and comparative examples will not give a detailed calculation process, and the calculation can be referred to Example 1 and Example 2.

[0058] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 70°C for 24 hours to form a prepolymer.

[0059] Steel sheet bonding experiment: 5 pairs of stainless steel sheets with a length of 10 cm and a width of 1 cm were butt-jointed with prepolymer coating. The coating bonding area was 1 × 1 cm 2 After fixing the bonding part with a dovetail clip, put it in a temperature of 160℃ for 6 hours and then cool it naturally at room temperature.

[0060] Adhesive shear strength test: The five pairs of steel sheets cured with the adhesive were tested by a tensile machine to obtain the curve of load (N) versus mechanical elongation (mm). The bond strength (MPa) was obtained by dividing the maximum load by the bonding area, and the average bond strength of the five samples was 10.68 MPa.

[0061] Example 3

[0062] Formula components: 53.5 parts of polyglutamic acid with a glutamic acid unit ratio of 50% and a molecular weight of 1000000 g / mol, 31 parts of epoxidized soybean oil, and 15.5 parts of tannic acid.

[0063] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 70°C for 24 hours to form a prepolymer.

[0064] Wood board bonding experiment: 5 pairs of birch wood boards with a length of 10 cm, a width of 2 cm, and a thickness of 1 cm were butt-jointed with prepolymer coating. The coating bonding area was 1 × 1 cm 2 After fixing the bonding part with a dovetail clip, place it in a 150°C temperature to cure for 1 hour. Then cool it naturally at room temperature.

[0065] Adhesive shear strength test: The five pairs of wood boards cured with the adhesive were tested by a tensile machine to obtain the curve of load (N) versus mechanical elongation (mm). The bond strength (MPa) was obtained by dividing the maximum load by the bonding area, and the average bond strength of the five samples was 2.54 MPa.

[0066] Example 4

[0067] Formula components: 59.2 parts of polyglutamic acid with a glutamic acid unit ratio of 40% and a molecular weight of 20,000,000 g / mol, 27.2 parts of epoxidized soybean oil, and 13.6 parts of tannic acid.

[0068] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 70°C for 1 hour to form a prepolymer.

[0069] Steel sheet bonding experiment: 5 pairs of stainless steel sheets with a length of 10 cm and a width of 1 cm were butt-jointed with prepolymer coating. The coating bonding area was 1 × 1 cm 2 , fix the bonding part with a dovetail clip, put it in 150℃ for curing for 6 hours, and then cool it naturally at room temperature.

[0070] Adhesive shear strength test: The five pairs of steel sheets cured with the adhesive were tested by a tensile machine to obtain the curve of load (N) versus mechanical elongation (mm). The bond strength (MPa) was obtained by dividing the maximum load by the bonding area, and the average bond strength of the five samples was 9.73 MPa.

[0071] Example 5

[0072] Formula components: 48.5 parts of polyglutamic acid with a glutamic acid unit ratio of 60% and a molecular weight of 1000000 g / mol, 34.4 parts of epoxidized soybean oil, and 17.1 parts of tannic acid.

[0073] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 80°C for 5 hours to form a prepolymer.

[0074] Steel sheet bonding experiment: 5 pairs of stainless steel sheets with a length of 10 cm and a width of 1 cm were butt-jointed with prepolymer coating. The coating bonding area was 1 × 1 cm 2After fixing the bonding part with a dovetail clip, put it in 170℃ for curing for 3 hours. Then cool it naturally at room temperature.

[0075] Adhesive shear strength test: The five pairs of steel sheets cured with the adhesive were tested by a tensile machine to obtain the curve of load (N) versus mechanical elongation (mm). The bond strength (MPa) was obtained by dividing the maximum load by the bonding area, and the average bond strength of the five samples was 8.57 MPa.

[0076] Example 6

[0077] Formula components: 63.2 parts of polyglutamic acid with a glutamic acid unit ratio of 50% and a molecular weight of 1000000 g / mol, and 36.8 parts of epoxidized soybean oil.

[0078] Preparation method of prepolymer: polyglutamic acid and epoxidized soybean oil are stirred and reacted at 70°C for 24 hours to form a prepolymer.

[0079] Steel sheet bonding experiment: 5 pairs of stainless steel sheets with a length of 10 cm and a width of 1 cm were butt-jointed with prepolymer coating. The coating bonding area was 1 × 1 cm 2 After fixing the bonding part with a dovetail clip, put it in a temperature of 160℃ for 6 hours and then cool it naturally at room temperature.

[0080] Adhesive shear strength test: The five pairs of steel sheets cured with the adhesive were tested by a tensile machine to obtain the curve of load (N) versus mechanical elongation (mm). The bond strength (MPa) was obtained by dividing the maximum load by the bonding area, and the average bond strength of the five samples was 4.85 MPa.

[0081] Comparative Example 1

[0082] An adhesive was prepared according to the method of Example 1, except that the mass ratio of polyglutamic acid in Comparative Example 1 was 68 wt %.

[0083] Formula components: 68 parts of polyglutamic acid with a glutamic acid unit ratio of 40% and a molecular weight of 100,000 g / mol, 31 parts of epoxidized soybean oil, and 1 part of tannic acid.

[0084] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 70°C for 6 hours to form a prepolymer.

[0085] The prepolymer formed has a high degree of reaction and forms a mass, which cannot be evenly coated for subsequent bonding. Subsequent bonding and bond strength testing are not possible.

[0086] Comparative Example 2

[0087] An adhesive was prepared according to the method of Example 1, except that the mass ratio of polyglutamic acid was 8 wt %.

[0088] Formula components: 8 parts of polyglutamic acid with a glutamic acid unit ratio of 40% and a molecular weight of 100,000 g / mol, 3.6 parts of epoxidized soybean oil, and 88.4 parts of tannic acid.

[0089] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 70°C for 6 hours to form a prepolymer.

[0090] Steel sheet bonding experiment: 5 pairs of stainless steel sheets with a length of 10 cm and a width of 1 cm were butt-jointed with prepolymer coating. The coating bonding area was 1 × 1 cm 2 After fixing the bonding part with a dovetail clip, place it in a 180℃ temperature to cure for 1 hour. Then cool it naturally at room temperature.

[0091] Adhesive shear strength test: The five pairs of steel sheets cured with the adhesive were tested by a tensile machine to obtain the curve of load (N) versus mechanical elongation (mm). The bond strength (MPa) was obtained by dividing the maximum load by the bonding area, and the average bond strength of the five samples was 0.84 MPa.

[0092] Comparative Example 3

[0093] An adhesive was prepared according to the method of Example 2, except that the molecular weight of polyglutamic acid was less than 1,000,000 g / mol.

[0094] Formula components: 53.5 parts of polyglutamic acid with a glutamic acid unit ratio of 50% and a molecular weight of 1000 g / mol, 31.1 parts of epoxidized soybean oil, and 15.4 parts of tannic acid.

[0095] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 70°C for 24 hours to form a prepolymer.

[0096] Steel sheet bonding experiment: 5 pairs of stainless steel sheets with a length of 10 cm and a width of 1 cm were butt-jointed with prepolymer coating. The coating bonding area was 1 × 1 cm 2 After fixing the bonding part with a dovetail clip, put it in a temperature of 160℃ for 6 hours and then cool it naturally at room temperature.

[0097] Adhesive shear strength test: The five pairs of steel sheets cured with the adhesive were tested by a tensile machine to obtain the curve of load (N) versus mechanical elongation (mm). The bond strength (MPa) was obtained by dividing the maximum load by the bonding area, and the average bond strength of the five samples was 0.95 MPa.

[0098] Comparative Example 4

[0099] An adhesive was prepared according to the method of Example 2, except that the molecular weight of polyglutamic acid was greater than 2,000,000 g / mol.

[0100] Formula components: 53.5 parts of polyglutamic acid with a glutamic acid unit ratio of 50% and a molecular weight of 3000000 g / mol, 31.1 parts of epoxidized soybean oil, and 15.4 parts of tannic acid.

[0101] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 70°C for 24 hours to form a prepolymer.

[0102] The prepolymer formed has a high degree of reaction and forms a mass, which cannot be evenly coated for subsequent bonding. Subsequent bonding and bond strength testing are not possible.

[0103] Comparative Example 5

[0104] An adhesive was prepared according to the method of Example 2, except that polyglutamic acid with a molecular weight of 1,000,000 g / mol was used, but the proportion of glutamic acid units was less than 40%.

[0105] Formula components: 53.5 parts of polyglutamic acid with a glutamic acid unit ratio of 30% and a molecular weight of 1000000 g / mol, 18.1 parts of epoxidized soybean oil, and 28.4 parts of tannic acid.

[0106] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 70°C for 24 hours to form a prepolymer.

[0107] Steel sheet bonding experiment: 5 pairs of stainless steel sheets with a length of 10 cm and a width of 1 cm were butt-jointed with prepolymer coating. The coating bonding area was 1 × 1 cm 2 After fixing the bonding part with a dovetail clip, put it in a temperature of 160℃ for 6 hours and then cool it naturally at room temperature.

[0108] Adhesive shear strength test: The five pairs of steel sheets cured with the adhesive were tested by a tensile machine to obtain the curve of load (N) versus mechanical elongation (mm). The bond strength (MPa) was obtained by dividing the maximum load by the bonding area, and the average bond strength of the five samples was 1.15 MPa.

[0109] Comparative Example 6

[0110] An adhesive was prepared according to the method of Example 2, except that polyglutamic acid with a molecular weight of 1,000,000 g / mol was used, but the proportion of glutamic acid units was greater than 60%.

[0111] Formula components: 53.5 parts of polyglutamic acid with a glutamic acid unit ratio of 70% and a molecular weight of 1000000 g / mol, 45 parts of epoxidized soybean oil, and 1.5 parts of tannic acid.

[0112] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 70°C for 24 hours to form a prepolymer.

[0113] The prepolymer formed has a high degree of reaction and forms a mass, which cannot be evenly coated for subsequent bonding. Subsequent bonding and bond strength testing are not possible.

[0114] Comparative Example 7

[0115] The adhesive was prepared according to the method of Example 2, except that the prepolymerization temperature was lower than 60°C.

[0116] Formula components: 53.5 parts of polyglutamic acid with a glutamic acid unit ratio of 50% and a molecular weight of 1000000 g / mol, 31.1 parts of epoxidized soybean oil, and 15.4 parts of tannic acid.

[0117] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 50°C for 24 hours to form a prepolymer.

[0118] The prepolymer formed has a very low viscosity. When bonding steel sheets, it basically flows out when fixed with a dovetail clamp. The amount of glue applied is very small. o C for 6 hours, then cooled to room temperature and stretched, it broke as soon as it was stretched. The reason may be that the amount of glue applied was too little.

[0119] Comparative Example 8

[0120] An adhesive was prepared according to the method of Example 2, except that the prepolymerization temperature was higher than 100°C.

[0121] Formula components: 53.5 parts of polyglutamic acid with a glutamic acid unit ratio of 50% and a molecular weight of 1000000 g / mol, 31.1 parts of epoxidized soybean oil, and 15.4 parts of tannic acid.

[0122] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 110° C. for 1 hour to form a prepolymer.

[0123] The prepolymer forms a non-sticky solid that is not easily spreadable.

[0124] Comparative Example 9

[0125] The adhesive was prepared according to the method of Example 2, except that the curing temperature of the adhesive was lower than 150 o C.

[0126] Formula components: 53.5 parts of polyglutamic acid with a glutamic acid unit ratio of 50% and a molecular weight of 1000000 g / mol, 31.1 parts of epoxidized soybean oil, and 15.4 parts of tannic acid.

[0127] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 70°C for 24 hours to form a prepolymer.

[0128] Steel sheet bonding experiment: 5 pairs of stainless steel sheets with a length of 10 cm and a width of 1 cm were butt-jointed with prepolymer coating. The coating bonding area was 1 × 1 cm 2 After fixing the bonding part with a dovetail clip, place it in a 140℃ temperature to cure for 8 hours. Then cool it naturally at room temperature.

[0129] Adhesive shear strength test: The five pairs of steel sheets cured with the adhesive were tested by a tensile machine to obtain the curve of load (N) versus mechanical elongation (mm). The bond strength (MPa) was obtained by dividing the maximum load by the bonding area, and the average bond strength of the five samples was 1.35 MPa.

[0130] Comparative Example 10

[0131] The adhesive was prepared according to the method of Example 2, except that the curing temperature of the adhesive was higher than 180 o C.

[0132] Formula components: 53.5 parts of polyglutamic acid with a glutamic acid unit ratio of 50% and a molecular weight of 1000000 g / mol, 31.1 parts of epoxidized soybean oil, and 15.4 parts of tannic acid.

[0133] Preparation method of prepolymer: polyglutamic acid, epoxy soybean oil and tannic acid are stirred and reacted at 70°C for 24 hours to form a prepolymer.

[0134] Steel sheet bonding experiment: 5 pairs of stainless steel sheets with a length of 10 cm and a width of 1 cm were butt-jointed with prepolymer coating. The coating bonding area was 1 × 1 cm 2 , fix the bonding part with a dovetail clip, put it in 190℃ for curing for 1 hour, and then cool it naturally at room temperature.

[0135] Adhesive shear strength test: The five pairs of steel sheets cured with the adhesive were tested by a tensile machine to obtain the curve of load (N) versus mechanical elongation (mm). The bond strength (MPa) was obtained by dividing the maximum load by the bonding area, and the average bond strength of the five samples was 1.67MPa.

[0136] It can be seen from the above embodiments and comparative examples that the preparation method of the polyglutamic acid / epoxidized soybean oil-based / tannic acid adhesive in the present invention can prepare an adhesive with higher bonding strength (greater than 2 MPa) only by controlling the contents of the appropriate polyglutamic acid, epoxy soybean oil-based, and tannic acid reactants, selecting the appropriate molecular weight of polyglutamic acid and glutamic acid content, and regulating the prepolymerization temperature and time, and the curing temperature and time, and thus may be applied in multiple fields.

[0137] 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 principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A polyglutamic acid / epoxidized soybean oil-based adhesive comprising the following raw materials in parts by weight: Polyglutamic acid: 10-65 parts, epoxidized soybean oil: 20-50 parts, tannic acid: 0-30 parts; The relative molecular weight of the polyglutamic acid is 100000-2000000 g / mol. The polyglutamic acid comprises glutamic acid units and sodium glutamate units, and the mass percentage of the glutamic acid units is 30-60%.

2. The polyglutamic acid / epoxidized soybean oil-based adhesive according to claim 1, characterized in that: The epoxy value of the epoxy soybean oil is greater than 0.6 mol / 100 g.

3. The polyglutamic acid / epoxidized soybean oil-based adhesive according to claim 1, characterized in that: The mass percentage of the glutamic acid unit is 40-60%.

4. The polyglutamic acid / epoxidized soybean oil-based adhesive according to claim 1, characterized in that: The weight proportion of polyglutamic acid is 30 to 65 parts.

5. The polyglutamic acid / epoxidized soybean oil-based adhesive according to claim 1, characterized in that: The weight proportion of tannic acid is 0 to 20 parts.

6. The polyglutamic acid / epoxidized soybean oil-based adhesive according to claim 1, characterized in that: The molar ratio of the carboxyl group in the polyglutamic acid to the epoxy group in the epoxidized soybean oil is 1:(0.9-1.1).

7. The method for preparing the polyglutamic acid / epoxidized soybean oil-based adhesive according to claim 1, comprising the following steps: A) mixing polyglutamic acid, epoxidized soybean oil and tannic acid to form a prepolymer; B) coating the prepolymer on the surface of the material to be bonded and curing the prepolymer to obtain a cured polyglutamic acid / epoxidized soybean oil-based adhesive.

8. The preparation method according to claim 7, characterized in that: The mixing temperature in step A) is 60-100° C., and the mixing time in step A) is 1-24 hours.

9. The preparation method according to claim 7, characterized in that: The curing temperature in step B) is 150-180° C., and the curing time in step B) is 1-8 hours.

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