Gelatin modified tough soybean protein water-based adhesive and preparation method thereof

Abstract

The invention discloses a gelatin-modified tough soybean protein water-based adhesive and a preparation method thereof, and the adhesive comprises the following components in parts by mass: 25 parts of soybean protein, 0-4.5 parts of gelatin-A, 0-4.5 parts of gelatin-B and 75 parts of a dispersion medium. The preparation method comprises the following specific steps: S1, weighing the components according to the mass ratio, dispersing the gelatin-A and the gelatin-B in a dispersion medium, and stirring in a water bath of 40 DEG C to completely dissolve the gelatin-A and the gelatin-B; s2, soybean protein is uniformly dispersed in the dispersion liquid of the gelatin-A and the gelatin-B obtained in the step S1, and then high-speed stirring is performed for 5 minutes, according to the gelatin-modified tough soybean protein water-based adhesive and the preparation method thereof, the generated adhesive can be connected with multiple matrixes through hydrogen bonds, electrostatic interaction or mechanical interlocking, and therefore tough adhesion is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of adhesives, in particular to a gelatin-modified tough soybean protein aqueous adhesive and a preparation method thereof. Background Art

[0002] Adhesives are found everywhere in our lives, such as in buildings, airplanes, cars, furniture, shoes, and packaging. Although traditional synthetic adhesives have the advantages of high performance and low cost, they also bring serious environmental problems. The petroleum raw materials of traditional adhesives are non-renewable and increasingly scarce. Toxic gases are released during use. For example, formaldehyde-based adhesives used in artificial boards release formaldehyde, which causes cancer. Discarded adhesives are difficult to chemically degrade, exacerbating the problem of microplastics.

[0003] Sustainable materials such as natural proteins and polysaccharides show great potential in replacing existing petroleum-based polymers. Protein meal, a byproduct of natural plant defatting, is abundant and inexpensive. Globulins and polysaccharides are the main components of plant proteins, however, they rely on limited secondary bond interactions. When preparing protein adhesives, they lack sustained and effective energy dissipation channels such as molecular chain entanglement, crystallization, and covalent cross-linking, and exhibit lower mechanical properties (strength and toughness). Performance and cost are eternal issues when developing new adhesive products to achieve sustainable development. Therefore, it is a major challenge to develop high-performance, low-cost sustainable bio-based adhesives. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] Therefore, the object of the present invention is to provide a gelatin-modified strong soy protein aqueous adhesive and a preparation method thereof, wherein the produced adhesive can be connected to a variety of substrates through hydrogen bonding, electrostatic action or mechanical interlocking, thereby achieving strong adhesion.

[0006] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions:

[0007] A gelatin-modified tough soybean protein water-based adhesive comprises the following components in parts by weight: 25 parts of soybean protein, 0-4.5 parts of gelatin-A, 0-4.5 parts of gelatin-B and 75 parts of a dispersion medium.

[0008] As a preferred embodiment of the gelatin-modified tough soy protein aqueous adhesive described in the present invention, gelatin-A is 0 parts, gelatin-B is 4.5 parts, or gelatin-A is 4.5 parts, gelatin-B is 0 parts, or gelatin-A is 1.5 parts, gelatin-B is 3 parts, or gelatin-A is 3 parts, gelatin-B is 1.5 parts.

[0009] As a preferred embodiment of the gelatin-modified tough soybean protein aqueous adhesive of the present invention, the protein content of the soybean protein is 53%, and the carbohydrate content is 33%.

[0010] As a preferred embodiment of the gelatin-modified tough soybean protein aqueous adhesive of the present invention, the particle size of the soybean protein is less than 200 meshes.

[0011] As a preferred embodiment of the gelatin-modified tough soybean protein aqueous adhesive described in the present invention, the dispersion medium is tap water or deionized water.

[0012] A method for preparing a gelatin-modified tough soybean protein aqueous adhesive, the specific steps are as follows:

[0013] S1. Weigh each component according to the mass ratio, disperse gelatin-A and gelatin-B in the dispersion medium, and stir in a 40°C water bath to completely dissolve gelatin-A and gelatin-B;

[0014] S2. Evenly disperse the soybean protein in the dispersion of gelatin-A and gelatin-B obtained in step S1, and then stir at high speed for 5 minutes.

[0015] As a preferred embodiment of the method for preparing a gelatin-modified tough soy protein aqueous adhesive according to the present invention, the gelatin-B is obtained by enzymatic hydrolysis of gelatin-A. The steps of preparing gelatin-B are as follows: gelatin-B is obtained by enzymatic hydrolysis of gelatin-A, specifically as follows:

[0016] First, 10 g of gelatin-A was added to a beaker containing 40 g of deionized water and stirred at 55 °C for 10 min;

[0017] Then add 0.01 g of bromelain to the beaker and stir at 600 rpm for 30 seconds;

[0018] The beaker was then quickly transferred to hot water at 95°C and stirred for 20 minutes to inactivate bromelain. Finally, solid gelatin-B powder was obtained by freeze drying.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention adopts gelatin-modified soybean protein adhesive. Gelatin-A and gelatin-B form a network skeleton through molecular self-assembly and interact with soybean protein through hydrogen bonds to improve the strength and toughness of the adhesive.

[0021] 2. The use of gelatin-B in the present invention helps to evenly disperse soybean globulin, promotes the interaction between globulin and the bonding interface, and improves the interfacial adhesion performance of the adhesive.

[0022] 3. The present invention is an adhesive for bonding at room temperature and does not contain organic volatiles such as formaldehyde, thereby solving the problems of oil resource consumption and organic volatile pollution in indoor air caused by traditional synthetic adhesives. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below in combination with the accompanying drawings and detailed embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0024] Figure 1 A schematic diagram of the molecular weight of gelatin in each embodiment provided by the present invention;

[0025] Figure 2 The morphology of the cured adhesive layer of the adhesive in Example 3 provided by the present invention and the existing adhesive;

[0026] Figure 3 This is a test diagram of the lap shear strength of the adhesive used in Examples 1-4 provided by the present invention on a wood-to-steel specimen;

[0027] Figure 4 This is a test diagram of the lap shear strength of the adhesive on different substrates in Example 3 provided by the present invention. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0029] Secondly, the present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0031] The invention provides a gelatin-modified strong soybean protein water-based adhesive and a preparation method thereof. The produced adhesive can be connected with a variety of substrates through hydrogen bonds, electrostatic effects or mechanical interlocking, thereby achieving strong adhesion.

[0032] The gelatin-modified toughened soy protein aqueous adhesive comprises the following components in parts by weight: 25 parts of soy protein, 0-4.5 parts of gelatin-A, 0-4.5 parts of gelatin-B and 75 parts of dispersion medium, specifically, 0 parts of gelatin-A, 4.5 parts of gelatin-B or 4.5 parts of gelatin-A, 0 parts of gelatin-B or 1.5 parts of gelatin-A, 3 parts of gelatin-B or 3 parts of gelatin-A, 1.5 parts of gelatin-B, the protein content of the soy protein is 53%, the carbohydrate content is 33%, the particle size of the soy protein is less than 200 meshes, and in this embodiment, the molecular weights of gelatin-A and gelatin-B are as follows: Figure 1 shown.

[0033] In order to verify the toughened soy protein aqueous adhesive modified with gelatin of the present invention, the following Examples 1-4 are provided.

[0034] Example 1

[0035] A method for preparing a gelatin-modified tough soybean protein aqueous adhesive comprises the following steps:

[0036] S1. Add 4.5 g of gelatin-B to 75 g of deionized water and stir in a 40°C water bath to completely dissolve the gelatin-B.

[0037] S2, adding 25g of soy protein to the mixture obtained in step S1, stirring for 5 minutes to disperse evenly; wherein, gelatin-B is obtained by enzymatic hydrolysis of gelatin-A, specifically as follows:

[0038] First, 10 g of gelatin-A was added to a beaker containing 40 g of deionized water and stirred at 55 °C for 10 min;

[0039] Then add 0.01 g of bromelain to the beaker and stir at 600 rpm for 30 seconds;

[0040] The beaker was then quickly transferred to hot water at 95°C and stirred for 20 minutes to inactivate bromelain. Finally, solid gelatin-B powder was obtained by freeze drying.

[0041] Example 2

[0042] A method for preparing a gelatin-modified tough soybean protein aqueous adhesive comprises the following steps:

[0043] S1. Add 1.5 g of gelatin-A and 3 g of gelatin-B to 75 g of deionized water, and stir in a 40°C water bath to completely dissolve gelatin-A and gelatin-B.

[0044] S2, adding 25g of soy protein to the mixture obtained in step S1, stirring for 5 minutes until it is evenly dispersed, wherein gelatin-B is obtained by enzymatic hydrolysis of gelatin-A, specifically as follows:

[0045] First, 10 g of gelatin-A was added to a beaker containing 40 g of deionized water and stirred at 55 °C for 10 min;

[0046] Then add 0.01 g of bromelain to the beaker and stir at 600 rpm for 30 seconds;

[0047] The beaker was then quickly transferred to hot water at 95°C and stirred for 20 minutes to inactivate bromelain. Finally, solid gelatin-B powder was obtained by freeze drying.

[0048] Example 3

[0049] A method for preparing a gelatin-modified tough soybean protein aqueous adhesive comprises the following steps:

[0050] S1. Add 3 g of gelatin-A and 1.5 g of gelatin-B to 75 g of deionized water, and stir in a 40°C water bath to completely dissolve gelatin-A and gelatin-B.

[0051] S2, adding 25g of soy protein to the mixture obtained in step S1, stirring for 5 minutes to disperse evenly; wherein, gelatin-B is obtained by enzymatic hydrolysis of gelatin-A, specifically as follows:

[0052] First, 10 g of gelatin-A was added to a beaker containing 40 g of deionized water and stirred at 55 °C for 10 min;

[0053] Then, 0.01 g of bromelain was added to the beaker and stirred at 600 rpm for 30 seconds. The beaker was then quickly transferred to 95° C. hot water and stirred for 20 minutes to inactivate the bromelain. Finally, solid gelatin-B powder was obtained by freeze drying.

[0054] Example 4

[0055] A method for preparing a gelatin-modified tough soybean protein aqueous adhesive comprises the following steps:

[0056] S1. Add 4.5 g of gelatin-A to 75 g of deionized water and stir in a 40°C water bath to completely dissolve the gelatin-A.

[0057] S2. Add 25 g of soy protein to the mixture obtained in step S1 and stir for 5 minutes until it is evenly dispersed.

[0058] Comparative Examples 1-3

[0059] Comparative Examples 1-3 use common water-based adhesives on the market, including polyvinyl acetate emulsion (PVAc), ethylene-vinyl acetate copolymer emulsion (EVA) and starch glue as comparative experiments.

[0060] The performance tests of the modified soybean protein adhesives prepared in Examples 1-4 of the present invention and the water-based adhesives of Comparative Examples 1-3 were performed according to the following method:

[0061] Adhesive performance evaluation experiment

[0062] The bonding strength of the adhesives of Examples 1-4 and Comparative Examples 1-3 to various substrates was evaluated mainly by lap shear test specimens. Considering that the room temperature curing of such adhesives is achieved on the basis of water volatilization, one of the substrates of the shear test specimens is fixed to wood. Wood, steel, glass, alumina ceramics, calcium silicate cement, fabric and cardboard were made into thin sheets for preparing shear test specimens. Except for glass and fabric (25×1×100mm 3 ) All substrates are 25×2×100mm in size 3 . Brush about 0.15g of adhesive on one end of the substrate board, then put the wooden board on it, check that it is about 25×25mm 2 The overlap area is clamped with two dovetail clamps to ensure a good fit. The prepared shear specimens are placed under ambient conditions (25°C, 40% humidity) for 24 hours, which is considered to be cured to equilibrium. All shear specimens were tested with INSTRON3366 at a tensile speed of 10 mm / min, and the maximum force was recorded and then divided by the bonding area to calculate the shear strength. Three specimens per group were averaged.

[0063] The lap shear strength test of the adhesive applied to wood-to-steel specimens in Examples 1-4 is shown in Tables 1 and Figure 2 As shown, the lap shear strength tests of the adhesive in Example 3 and the adhesive in Comparative Examples 1-3 on different substrates are shown in Table 2.

[0064] Table 1 - Shear strength of wood-to-steel specimens of adhesives in Examples 1-4 (MPa)

[0065] Test sample Wood-to-steel lap shear strength Example 1 2.83 Example 2 3.28 Example 3 3.65 Example 4 3.48

[0066] Table 2 - Lap shear strength of adhesives for different substrates in Example 3 and Comparative Examples 1-3 (MPa)

[0067] Test sample Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 wood against wood 3.51 3.68 3.06 2.42 wood versus steel 3.65 0.72 2.65 1.74 Wood vs. Glass 2.47 0.82 1.56 0.85 Wood vs. Ceramics 2.58 1.96 1.78 1.54 Wood vs. Cement 1.33 1.23 1.35 1.26 Wood on paper 1.08 1.01 1.15 1.10 Wood vs Fabric 0.62 0.58 0.65 0.56

[0068] As shown in Table 2, compared with the comparative example, the adhesive of the present application has better comprehensive performance, is derived from biomass raw materials, and is more sustainable. By observing the surface morphology of the cured adhesive film, the toughness of the cured adhesive layer is judged. The experimental results are as follows Figure 2 As shown, the soybean protein adhesive of the present invention does not have the problem of formaldehyde release and consumption of petroleum-based raw materials, has fewer holes and cracks on the surface of the cured adhesive layer, forms an adhesive layer with a uniform and dense structure, and Figure 4 As shown, the lap shear strength of the soy protein adhesive for wood and steel in the embodiment is above 3.5 MPa, indicating that the toughness of the modified adhesive is improved.

[0069] In summary, the invented adhesive is mainly composed of a soybean powder matrix and a gelatin skeleton. Soy powder contains globular proteins and polysaccharides, which can enhance interfacial adhesion and withstand loads. Gelatin-A can be enzymatically hydrolyzed to obtain gelatin-B with a smaller molecular weight. Some gelatin-A and gelatin-B segments self-assemble into a collagen triple helix structure to form a stable three-dimensional mesh skeleton, which mainly maintains the cohesion of the adhesive system and promotes the interfacial adhesion of soybean globulin. The soybean protein matrix and the gelatin-A / gelatin-B skeleton are connected together through supramolecular interactions based on hydrogen bonds. The resulting adhesive can be connected to a variety of matrices through hydrogen bonds, electrostatic effects or mechanical interlocking, thereby achieving strong and tough adhesion. This adhesive has adjustable and convenient application properties, such as room temperature adhesion and on-demand separation.

[0070] Although the present invention has been described above with reference to the embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed in the present invention may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A gelatin-modified tough soybean protein aqueous adhesive, characterized in that: The invention comprises the following components in parts by weight: 25 parts of soybean protein, 0-4.5 parts of gelatin-A, 0-4.5 parts of gelatin-B and 75 parts of dispersion medium.

2. The gelatin-modified tough soybean protein aqueous adhesive according to claim 1, characterized in that: Gelatin-A is 0 parts and gelatin-B is 4.5 parts, or gelatin-A is 4.5 parts and gelatin-B is 0 parts, or gelatin-A is 1.5 parts and gelatin-B is 3 parts, or gelatin-A is 3 parts and gelatin-B is 1.5 parts.

3. The gelatin-modified tough soybean protein aqueous adhesive according to claim 1, characterized in that: The soy protein contains 53% protein and 33% carbohydrate.

4. The gelatin-modified tough soybean protein aqueous adhesive according to claim 1, characterized in that: The particle size of the soy protein is less than 200 meshes.

5. The gelatin-modified tough soybean protein aqueous adhesive according to claim 1, characterized in that: The dispersion medium is tap water or deionized water.

6. A method for preparing a gelatin-modified tough soybean protein aqueous adhesive as claimed in any one of claims 1 to 5, characterized in that: The specific steps are as follows: S1. Weigh each component according to the mass ratio, disperse gelatin-A and gelatin-B in the dispersion medium, and stir in a 40°C water bath to completely dissolve gelatin-A and gelatin-B; S2. Evenly disperse the soybean protein in the dispersion of gelatin-A and gelatin-B obtained in step S1, and then stir at high speed for 5 minutes.

7. The method for preparing a gelatin-modified tough soybean protein aqueous adhesive according to claim 1, characterized in that: The gelatin-B is obtained by enzymatic hydrolysis of gelatin-A, and the preparation method of the gelatin-B is as follows: First, 10 g of gelatin-A was added to a beaker containing 40 g of deionized water and stirred at 55 °C for 10 min; Then add 0.01 g of bromelain to the beaker and stir at 600 rpm for 30 seconds; The beaker was then quickly transferred to hot water at 95°C and stirred for 20 minutes to inactivate bromelain. Finally, solid gelatin-B powder was obtained by freeze drying.

Images