Adhesive based on abietic acid grafted copolymerized soybean protein as well as preparation method and application of adhesive

Abstract

The invention relates to an adhesive based on abietic acid grafted copolymerized soybean protein as well as a preparation method and application of the adhesive. The adhesive is prepared from the following raw materials: soybean protein isolate, an anionic surfactant, an initiator, epoxy chloropropane, abietic acid, dopamine hydrochloride and water. The invention provides a preparation method of an adhesive, which comprises the following steps: mixing abietic acid, an alcohol solvent, hydroquinone and water to obtain a abietic acid solution; mixing soybean protein isolate, an anionic surfactant and water to obtain a mixed material; adding an initiator into the mixed material, adjusting the pH value to be alkaline, and carrying out gelatinization reaction to obtain a gelatinized product; and adding epoxy chloropropane and an abietic acid solution into the gelatinized product, carrying out graft copolymerization reaction, cooling, and adding dopamine hydrochloride to obtain the adhesive. In addition, the invention discusses the application of the adhesive in materials such as artificial boards, metal and glass. The soybean protein-based adhesive solves the problem that the existing soybean protein-based adhesive is insufficient in strength, mildew resistance and flame retardance.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesive materials, and in particular, to an adhesive, a preparation method and an application based on rosin acid graft copolymerized soy protein. Background Art

[0002] In the wood manufacturing industry, artificial boards play an important role in the production and manufacturing of the home decoration market, packaging industry and construction industry due to their economic benefits and excellent processing performance. As a key material in the processing and manufacturing of artificial boards, adhesives are widely used because of their low cost and high bonding strength. However, the main adhesives currently used in the artificial board industry are formaldehyde-based adhesives. As a Class I carcinogen, formaldehyde has caused serious harm to the environment and human health. Long-term exposure to formaldehyde can lead to respiratory diseases, allergic reactions and even cancer, seriously affecting human health and quality of life.

[0003] In order to solve the environmental and health problems caused by formaldehyde-based adhesives, bio-based adhesives, as a new type of environmental protection product, have attracted wide attention. In recent years, biomass materials such as starch, lignin, tannin and protein have gradually become research hotspots due to their non-toxic, green and renewable characteristics. Bio-based adhesives are expected to reduce the consumption of petrochemical resources and lower indoor formaldehyde emissions, and have great potential to replace traditional formaldehyde-based adhesives. Among them, soy protein adhesives are considered to be one of the most promising alternatives due to their low price, rich reserves, renewable and easy processing. However, soy protein adhesives still have some defects in practical applications, such as poor bonding strength, poor water resistance and insufficient flame retardancy, which limit their wide application.

[0004] At present, the modification research on soy protein adhesives mainly focuses on methods such as bio-enzymatic method, chemical cross-linking modification, physical modification and filler mixing. However, most modification methods still rely on non-renewable petroleum-based substances for cross-linking modification, which not only violates the original intention of green environmental protection, but also hinders the sustainable development of bio-based materials. Therefore, developing a modification method based on natural plant-based cross-linking agents to improve the bonding performance, flame retardancy and mildew resistance of soy protein adhesives while maintaining environmental protection performance has become the focus of current research.

[0005] In the prior art, a preparation method of a fully bio-based two-component soy adhesive has been disclosed. This adhesive is made from raw materials such as soy protein base material, mixture A, cross-linking curing agent B, phytic acid, alkali and deionized water. This adhesive modifies the soy protein base material through a biomass cross-linking agent, but its application range is relatively limited and it is only suitable for the bonding of artificial boards. In addition, this adhesive has poor mildew resistance and is not suitable for bonding a variety of different substrates, thus limiting its wide application in actual production. Summary of the Invention

[0006] The purpose of the present invention is to provide an adhesive based on rosin acid grafted copolymerized soybean protein, a preparation method and application, so as to solve the problems of low bonding strength, insufficient flame retardancy and mildew resistance of existing soybean protein-based adhesives, and to expand the application range of the adhesive.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] The invention discloses an adhesive based on rosin acid grafted copolymerized soybean protein, the raw materials of which include: soybean protein isolate, anionic surfactant, initiator, epichlorohydrin, rosin acid, anhydrous ethanol, sodium hydroxide, hydroquinone, dopamine hydrochloride and water.

[0009] According to the above technical means, by cleverly combining soy protein isolate, anionic surfactants, initiators, epichlorohydrin, rosin acid and dopamine hydrochloride, the bonding strength, flame retardant properties and mildew resistance of the adhesive are effectively improved. Among them, the use of soy protein isolate as the main raw material, as a renewable resource, reduces dependence on fossil fuels and reduces environmental pollution; since soy protein isolate and rosin acid are both processed from natural products, they have no toxic side effects on the human body, are more biodegradable, and are environmentally friendly, which significantly reduces the environmental pollution problems of the adhesive processing and manufacturing industry; the addition of anionic surfactants effectively changes the spiral winding structure of soy protein isolate and enhances the degree of cross-linking reaction, thereby improving the bonding effect of the adhesive, while improving the dispersibility and stability of the adhesive; the unique tricyclic diterpenoid structure in rosin acid is used to react with free radicals in soy protein to form a complex cross-linking structure, thereby effectively delaying the oxidative degradation of the adhesive and enhancing the mildew resistance of the adhesive; in addition, due to the rosin acid itself It has a certain viscosity, and after the graft copolymerization reaction with soy protein, a large number of hydrogen bonds and van der Waals forces are generated, which greatly improves the bonding performance of the adhesive; the addition of epichlorohydrin reacts with the active groups in rosin acid to form a cross-linking agent with viscous properties, and the hydrolysis coupling grafting effect between the formed cross-linking agent and the soy protein isolate is used to further increase the bonding performance of the adhesive and the water resistance after curing; the addition of dopamine hydrochloride further improves the flame retardant properties of the adhesive, and forms a more complex cross-linked network structure through the Michael addition reaction between the soy protein and the rosin acid solution, thereby enhancing the bonding strength and flame retardant properties of the adhesive after curing, making it suitable for more complex working environments; soy protein is relatively cheap and widely available, which helps to reduce production costs.

[0010] Among them, natural rosin acid, as an abundant secondary metabolite, is mainly distilled from pine trees and pulp waste. Rosin acid is a tricyclic diterpenoid compound. Through experimental research, it has been proven that its unique structure enables it to react with the active groups in soy protein to form a dense hybrid network structure, thereby significantly improving the adhesion performance of the adhesive. In addition, the rosin acid molecule contains a large number of active carboxyl groups, with high reactivity. At the same time, its hydrophobic structure also helps to improve the water resistance of the adhesive.

[0011] Preferably, by weight, it includes the following raw materials: 10-20 parts by weight of soy protein isolate, 1-3 parts by weight of anionic surfactant, 0.1-0.9 parts by weight of initiator, 0.05-2 parts by weight of epichlorohydrin, 0.05-0.6 parts by weight of rosin acid, 0.1-0.5 parts by weight of dopamine hydrochloride, and 75-100 parts by weight of water.

[0012] Preferably, by weight, it includes the following raw materials: 10-15 parts by weight of soy protein isolate, 1.8-2 parts by weight of anionic surfactant, 0.6 parts by weight of initiator, 0.05-1.5 parts by weight of epichlorohydrin, 0.2-0.4 parts by weight of rosin acid, 0.1-0.3 parts by weight of dopamine hydrochloride, and 85 parts by weight of water.

[0013] Preferably, by weight, it includes the following raw materials: 15 parts by weight of soy protein isolate, 1.8 parts by weight of anionic surfactant, 0.6 parts by weight of initiator, 0.1 parts by weight of epichlorohydrin, 0.3 parts by weight of rosin acid, 0.1 parts by weight of dopamine hydrochloride, and 85 parts by weight of water.

[0014] Preferably, the soy protein isolate is selected from soy protein isolate powder.

[0015] Preferably, the initiator is selected from ammonium persulfate.

[0016] Preferably, the anionic surfactant is selected from one or two of sodium N-acylaminocarboxylate, sodium dodecylsulfonate, and sodium dodecyl sulfate;

[0017] Preferably, the solid content of the rosin acid solution is 40-60 wt%.

[0018] By controlling the solid content of the rosin acid solution between 40-60 wt%, it is possible to ensure that the rosin acid has a moderate concentration and reactivity in the reaction system, thereby effectively improving the performance of the adhesive. If the solid content is too high (>60 wt%), it may cause aggregation of rosin acid molecules, reducing its dispersibility and reaction efficiency; if the solid content is too low (<40 wt%), it may lead to insufficient concentration of rosin acid and inability to effectively carry out graft copolymerization reaction with soy protein.

[0019] Among them, the main role of rosin acid is to react with the active groups (such as amino groups, hydroxyl groups, etc.) in soy protein to form a dense cross-linked network structure, thereby improving the bonding strength, water resistance, mildew resistance and thermal stability of the adhesive. By controlling the solid content of the rosin acid solution, the reaction degree of rosin acid and soy protein can be precisely adjusted to avoid over-crosslinking (resulting in brittle adhesive) or insufficient crosslinking (resulting in unqualified performance), so as to optimize the comprehensive performance of the adhesive.

[0020] The present invention also provides a preparation method of an adhesive based on rosin acid graft copolymerized soy protein, comprising the following steps:

[0021] Mix rosin acid, an alcohol solvent, hydroquinone and water to obtain a rosin acid solution;

[0022] Mix soy protein isolate, an anionic surfactant and water to obtain a mixed material;

[0023] Add an initiator to the mixed material, adjust the pH of the mixed material to be alkaline, and carry out a gelatinization reaction to obtain a gelatinized product;

[0024] Add epichlorohydrin and the rosin acid solution to the gelatinized product, carry out a graft copolymerization reaction, and add dopamine hydrochloride after cooling to obtain an adhesive based on rosin acid graft copolymerized soy protein.

[0025] According to the above technical means, by adjusting the pH value of the mixed material to be alkaline, the degree of the gelatinization reaction is effectively controlled, thereby ensuring the performance of the final product. The method of co-mixing and heating to dissolve soy protein isolate and an anionic surfactant is beneficial to changing the helical winding structure of soy protein isolate, enhancing the degree of crosslinking reaction and improving the bonding effect of the water-based adhesive. By adding epichlorohydrin and the rosin acid solution to the gelatinized product for graft copolymerization reaction, the hydrolysis coupling grafting effect between the viscous crosslinking agent generated by the reaction of epichlorohydrin and the rosin acid solution and soy protein isolate is utilized to further improve the performance of the adhesive, including bonding strength and water resistance, etc. The addition of dopamine hydrochloride further optimizes the flame retardant performance and bonding performance of the adhesive, making it suitable for a variety of different application scenarios. In addition, this preparation method has the advantages of simple operation and mild process conditions, and is easy to realize industrial production, so it has wide popularization and practical value in the field of adhesive material technology.

[0026] Preferably, the temperature of the gelatinization reaction is 60-65°C.

[0027] Preferably, the time of the gelatinization reaction is 20-35 min.

[0028] Preferably, the temperature of the gelatinization reaction is 60°C.

[0029] Preferably, the time of the gelatinization reaction is 30 min.

[0030] Preferably, the temperature of the graft copolymerization reaction is 55-65 °C.

[0031] Preferably, the time of the graft copolymerization reaction is 10-25 min.

[0032] Preferably, an alkali is used to adjust the pH of the mixed material to 9-10.

[0033] Preferably, the alkali is selected from sodium hydroxide.

[0034] Preferably, the alcohol solvent is selected from at least one of methanol, ethanol, and propanol.

[0035] Preferably, after cooling to room temperature, hydroxypropyl methylcellulose is added, and the mixture is stirred evenly to obtain a soy protein-based aqueous adhesive.

[0036] Preferably, the preparation method includes the following steps:

[0037] S1. Mix rosin acid, absolute ethanol, hydroquinone, and water, add them to a reaction vessel, and stir and disperse at room temperature to obtain a rosin acid solution;

[0038] S2. Mix soy protein isolate, an anionic surfactant, and water, add them to a reaction vessel, and stir and disperse to obtain a mixed material;

[0039] S3. Add an initiator to the mixed material, use sodium hydroxide to adjust the pH of the mixed material to 9-10, heat to 60-65 °C under stirring conditions, and carry out a gelatinization reaction for 30-35 min to obtain a gelatinized product;

[0040] S4. Add epichlorohydrin and the rosin acid solution to the gelatinized product, heat to 55-65 °C under stirring conditions, carry out a graft copolymerization reaction for 10-25 min, cool to room temperature, add dopamine hydrochloride, and stir and mix evenly to obtain an adhesive based on rosin acid-grafted copolymerized soy protein.

[0041] The present invention also provides an application of the adhesive based on rosin acid-grafted copolymerized soy protein as described in the present invention as an adhesive in wood-based panels, metals, and glass.

[0042] Preferably, when the adhesive based on rosin acid-grafted copolymerized soy protein is used for bonding wood-based panels, the hot pressing temperature is 120-200 °C.

[0043] Preferably, when the adhesive based on rosin acid-grafted copolymerized soy protein is used for bonding three-layer poplar veneers, the hot pressing temperature is 140 °C.

[0044] Preferably, when the adhesive based on rosin acid graft copolymerized soy protein is used for bonding metals, the hot pressing temperature is 90 - 130 °C.

[0045] Preferably, when the adhesive based on rosin acid graft copolymerized soy protein is used for bonding iron sheets and copper sheets, the hot pressing temperature is 120 °C.

[0046] Preferably, when the adhesive based on rosin acid graft copolymerized soy protein is used for bonding glass, the hot pressing temperature is 55 - 80 °C.

[0047] Preferably, when the adhesive based on rosin acid graft copolymerized soy protein is used for bonding glass, the hot pressing temperature is 70 °C.

[0048] The beneficial effects of the present invention are as follows:

[0049] 1) For the adhesive based on rosin acid graft copolymerized soy protein of the present invention, by skillfully combining soy protein isolate, anionic surfactant, initiator, epichlorohydrin, rosin acid and dopamine hydrochloride, the bonding strength, mildew resistance and flame retardant performance of the adhesive are significantly improved. Among them, soy protein isolate is used as the main raw material, making full use of renewable resources, reducing the dependence on fossil fuels, and thus reducing environmental pollution. In addition, since both soy protein isolate and rosin acid are natural products, they have the characteristics of non-toxic side effects and are easy to biodegradable, so they are environmentally friendly and significantly reduce the environmental pollution problems in the production process of the adhesive. The addition of anionic surfactant effectively changes the helical winding structure of soy protein isolate, enhances the degree of crosslinking reaction, thus improving the bonding effect of the adhesive, and at the same time improving the dispersibility and stability of the adhesive. The unique tricyclic diterpenoid structure in rosin acid reacts with free radicals in soy protein to form a complex crosslinked structure, thus effectively delaying the oxidative degradation of the adhesive and enhancing the mildew resistance of the adhesive; in addition, due to the certain viscosity of rosin acid itself, a large number of hydrogen bonds and van der Waals forces are generated after the graft copolymerization reaction with soy protein, greatly improving the bonding performance of the adhesive. By adding epichlorohydrin to react with the active groups in rosin acid to form a crosslinking agent with viscous characteristics, and using the hydrolysis coupling grafting effect between the formed crosslinking agent and soy protein isolate, the bonding performance of the adhesive and the water resistance after curing are further increased. The addition of dopamine hydrochloride further improves the flame retardant performance of the adhesive, and forms a more complex crosslinked network structure through the Michael addition reaction with soy protein isolate and rosin acid solution, enhancing the bonding strength and flame retardant performance after curing of the adhesive, making it suitable for more complex working environments. In addition, the relatively low price and wide source of soy protein help to reduce production costs.

[0050] 2) The preparation method of the adhesive based on rosin acid graft copolymerized soy protein of the present invention effectively controls the degree of gelatinization reaction by adjusting the pH value of the mixed materials to alkaline, thereby ensuring the performance of the final product. The method of co-mixing and heating to dissolve soy protein isolate and anionic surfactant helps to change the helical winding structure of soy protein isolate and enhance the degree of crosslinking reaction, thus improving the bonding effect of the water-based adhesive. By adding epichlorohydrin and rosin acid solution to the gelatinized product for graft copolymerization reaction, the viscous crosslinking agent formed by the reaction of epichlorohydrin and rosin acid solution and the hydrolysis coupling grafting effect between it and soy protein isolate are used to further improve the performance of the adhesive, such as bonding strength and water resistance. Adding hydrochloric acid dopamine can undergo Michael addition reaction with the adhesive to form a more complex and stable network structure, thereby further optimizing the bonding performance and flame retardant performance of the adhesive and making it suitable for a variety of different application scenarios. In addition, this preparation method has the advantages of simple operation and mild process conditions, is easy to realize industrial production, and has wide popularization and practical value in the field of adhesive material technology. Brief Description of the Drawings

[0051] Figure 1 is a flowchart of the preparation method of the adhesive based on rosin acid graft copolymerized soy protein of the present invention;

[0052] Figure 2 is a lap joint test diagram between metal veneer and glass veneer for the adhesives prepared in Examples 1 to 5;

[0053] Figure 3 is a diagram of the vertical drop result and side knock result after glass veneer bonding for the adhesive prepared in Example 3;

[0054] Figure 4 is a Fourier transform infrared spectroscopy (FTIR) diagram of the adhesives prepared in Example 3, Comparative Example 1 and Comparative Example 2;

[0055] Figure 5 is the thermogravimetric curve (TG) and thermogravimetric derivative curve (DTG) of the adhesives prepared in Examples 1 to 4, Comparative Example 1 and Comparative Example 2. Detailed Embodiments

[0056] The following will illustrate the embodiments of the present invention with reference to the drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, rather than for limiting the protection scope of the present invention.

[0057] Example 1

[0058] As Figure 1 shown, a preparation method of an adhesive based on rosin acid graft copolymerized soy protein includes the following steps:

[0059] S1. Add 0.1 g of rosin acid particles, 0.1 g of hydroquinone, 3 g of absolute ethanol and 3 g of deionized water into a reaction vessel, and stir evenly at room temperature to obtain a uniformly dispersed rosin acid solution;

[0060] S2. Add 20 g of soy protein isolate (SPI), 2.4 g of sodium dodecyl sulfonate and 100 g of deionized water into a reaction kettle and stir to disperse, forming a uniformly mixed mixture;

[0061] S3. Add 0.60 g of ammonium persulfate to the mixture obtained in S2, and add sodium hydroxide to adjust the pH of the mixture to 9. Carry out a gelatinization reaction under stirring conditions to obtain a viscous liquid, that is, a gelatinized product; the temperature of the gelatinization reaction is 60 °C, and the time of the gelatinization reaction is 25 min;

[0062] S4. Add 0.1 g of epichlorohydrin and the rosin acid solution obtained in S1 to the gelatinized product obtained in S3, and carry out a graft copolymerization reaction under stirring conditions. The temperature of the graft copolymerization reaction is 55 °C, and the time of the graft copolymerization reaction is 15 min. After the graft copolymerization reaction is completed, cool the obtained material to room temperature, add 0.1 g of dopamine hydrochloride, and stir and mix evenly to obtain an adhesive based on rosin acid graft copolymerized soy protein.

[0063] Example 2

[0064] As Figure 1 shown, a preparation method of an adhesive based on rosin acid graft copolymerized soy protein includes the following steps:

[0065] S1. Add 0.2 g of rosin acid particles, 0.2 g of hydroquinone, 5 g of absolute ethanol and 5 g of deionized water into a reaction vessel, and stir evenly at room temperature to obtain a uniformly dispersed rosin acid solution;

[0066] S2. Add 20 g of soy protein isolate (SPI), 2.4 g of sodium dodecyl sulfonate and 100 g of deionized water into a reaction kettle and stir to disperse, forming a uniformly mixed mixture;

[0067] S3. Add 0.60 g of ammonium persulfate to the mixture obtained in S2, and add sodium hydroxide to adjust the pH of the mixture to 9. Carry out a gelatinization reaction under stirring conditions to obtain a viscous liquid, that is, a gelatinized product; the temperature of the gelatinization reaction is 60 °C, and the time of the gelatinization reaction is 25 min;

[0068] S4. Add 0.1 g of epichlorohydrin and the rosin acid solution obtained in S1 to the gelatinized product obtained in S3, and carry out a graft copolymerization reaction under stirring conditions. The temperature of the graft copolymerization reaction is 55 °C, and the time of the graft copolymerization reaction is 15 min. After the graft copolymerization reaction is completed, cool the obtained material to room temperature, add 0.1 g of dopamine hydrochloride, and stir and mix evenly to obtain an adhesive based on rosin acid graft copolymerized soy protein.

[0069] Example 3

[0070] As Figure 1 shown, a preparation method of an adhesive based on rosin acid graft copolymerized soy protein includes the following steps:

[0071] S1. Add 0.3 g of rosin acid particles, 0.3 g of hydroquinone, 8 g of absolute ethanol and 8 g of deionized water to a reaction vessel, and stir evenly at room temperature to obtain a uniformly dispersed rosin acid solution;

[0072] S2. Add 20 g of soy protein isolate (SPI), 2.4 g of sodium dodecyl sulfate and 100 g of deionized water to a reaction kettle and stir to disperse, forming a uniformly mixed mixture;

[0073] S3. Add 0.60 g of ammonium persulfate to the mixture obtained in S2, and add sodium hydroxide to adjust the pH of the mixture to 9. Carry out a gelatinization reaction under stirring conditions to obtain a viscous liquid, i.e., a gelatinized product; the temperature of the gelatinization reaction is 60 °C, and the time of the gelatinization reaction is 25 min;

[0074] S4. Add 0.1 g of epichlorohydrin and the rosin acid solution obtained in S1 to the gelatinized product obtained in S3, and carry out a graft copolymerization reaction under stirring conditions. The temperature of the graft copolymerization reaction is 55 °C, and the time of the graft copolymerization reaction is 15 min. After the graft copolymerization reaction is completed, cool the obtained material to room temperature, add 0.1 g of dopamine hydrochloride, and stir and mix evenly to obtain an adhesive based on rosin acid graft copolymerized soy protein.

[0075] Example 4

[0076] As Figure 1 shown, a preparation method of an adhesive based on rosin acid graft copolymerized soy protein includes the following steps:

[0077] S1. Add 0.4 g of rosin acid particles, 0.4 g of hydroquinone, 10 g of absolute ethanol and 10 g of deionized water to a reaction vessel, and stir evenly at room temperature to obtain a uniformly dispersed rosin acid solution;

[0078] S2. Add 20 g of soy protein isolate (SPI), 2.4 g of sodium dodecyl sulfate, and 100 g of deionized water into a reaction kettle and stir to disperse, forming a uniformly mixed material.

[0079] S3. Add 0.60 g of ammonium persulfate into the mixed material obtained in S2, and add sodium hydroxide to adjust the pH of the mixed material to 9. Conduct a gelatinization reaction under stirring conditions to obtain a viscous liquid, i.e., the gelatinized product. The temperature of the gelatinization reaction is 60 °C, and the time of the gelatinization reaction is 25 min.

[0080] S4. Add 0.1 g of epichlorohydrin and the rosin acid solution obtained in S1 into the gelatinized product obtained in S3, and conduct a graft copolymerization reaction under stirring conditions. The temperature of the graft copolymerization reaction is 55 °C, and the time of the graft copolymerization reaction is 15 min. After the graft copolymerization reaction is completed, cool the obtained material to room temperature, add 0.1 g of dopamine hydrochloride, and stir to mix evenly to obtain an adhesive based on rosin acid graft copolymerized soy protein.

[0081] Example 5

[0082] As Figure 1 shown, a preparation method of an adhesive based on rosin acid graft copolymerized soy protein includes the following steps:

[0083] S1. Add 0.1 g of rosin acid particles, 0.1 g of hydroquinone, 3 g of absolute ethanol, and 3 g of deionized water into a reaction vessel, and stir evenly at room temperature to obtain a uniformly dispersed rosin acid solution.

[0084] S2. Add 20 g of soy protein isolate (SPI), 2.4 g of sodium dodecyl sulfate, and 100 g of deionized water into a reaction kettle and stir to disperse, forming a uniformly mixed material.

[0085] S3. Add 0.60 g of ammonium persulfate into the mixed material obtained in S2, and add sodium hydroxide to adjust the pH of the mixed material to 9. Conduct a gelatinization reaction under stirring conditions to obtain a viscous liquid, i.e., the gelatinized product. The temperature of the gelatinization reaction is 60 °C, and the time of the gelatinization reaction is 25 min.

[0086] S4. Add 0.1 g of epichlorohydrin and the rosin acid solution obtained in S1 into the gelatinized product obtained in S3, and conduct a graft copolymerization reaction under stirring conditions. The temperature of the graft copolymerization reaction is 55 °C, and the time of the graft copolymerization reaction is 15 min. After the graft copolymerization reaction is completed, cool the obtained material to room temperature, add 0.2 g of dopamine hydrochloride, and stir to mix evenly to obtain an adhesive based on rosin acid graft copolymerized soy protein.

[0087] Example 6

[0088] AsFigure 1 As shown in the figure, a preparation method of an adhesive based on rosin acid graft copolymerized soy protein includes the following steps:

[0089] S1. Add 0.2 g of rosin acid particles, 0.2 g of hydroquinone, 5 g of absolute ethanol and 5 g of deionized water into a reaction vessel, stir evenly at room temperature to obtain a uniformly dispersed rosin acid solution;

[0090] S2. Add 20 g of soy protein isolate (SPI), 2.4 g of sodium dodecyl sulfonate and 100 g of deionized water into a reaction kettle, stir and disperse to form a uniformly mixed material;

[0091] S3. Add 0.60 g of ammonium persulfate to the mixed material obtained in S2, and add sodium hydroxide to adjust the pH of the mixed material to 9. Carry out a gelatinization reaction under stirring to obtain a viscous liquid, that is, a gelatinized product; the temperature of the gelatinization reaction is 60 °C, and the time of the gelatinization reaction is 25 min;

[0092] S4. Add 0.1 g of epichlorohydrin and the rosin acid solution obtained in S1 to the gelatinized product obtained in S3, carry out a graft copolymerization reaction under stirring. The temperature of the graft copolymerization reaction is 55 °C, and the time of the graft copolymerization reaction is 15 min. After the graft copolymerization reaction is completed, cool the obtained material to room temperature, add 0.2 g of dopamine hydrochloride, stir and mix evenly to obtain an adhesive based on rosin acid graft copolymerized soy protein.

[0093] Example 7

[0094] As Figure 1 shown in the figure, a preparation method of an adhesive based on rosin acid graft copolymerized soy protein includes the following steps:

[0095] S1. Add 0.3 g of rosin acid particles, 0.3 g of hydroquinone, 8 g of absolute ethanol and 8 g of deionized water into a reaction vessel, stir evenly at room temperature to obtain a uniformly dispersed rosin acid solution;

[0096] S2. Add 20 g of soy protein isolate (SPI), 2.4 g of sodium dodecyl sulfonate and 100 g of deionized water into a reaction kettle, stir and disperse to form a uniformly mixed material;

[0097] S3. Add 0.60 g of ammonium persulfate to the mixed material obtained in S2, and add sodium hydroxide to adjust the pH of the mixed material to 9. Carry out a gelatinization reaction under stirring to obtain a viscous liquid, that is, a gelatinized product; the temperature of the gelatinization reaction is 60 °C, and the time of the gelatinization reaction is 25 min;

[0098] S4. Add 0.1 g of epichlorohydrin and the rosin acid solution obtained in S1 to the gelatinized product obtained in S3, and carry out graft copolymerization reaction under stirring conditions. The temperature of the graft copolymerization reaction is 55 °C, and the time of the graft copolymerization reaction is 15 min. After the graft copolymerization reaction is completed, cool the obtained material to room temperature, add 0.3 g of dopamine hydrochloride, and stir and mix evenly to obtain an adhesive based on rosin acid graft copolymerized soy protein.

[0099] Example 8

[0100] As Figure 1 shown, a preparation method of an adhesive based on rosin acid graft copolymerized soy protein includes the following steps:

[0101] S1. Add 0.4 g of rosin acid particles, 0.4 g of hydroquinone, 10 g of absolute ethanol and 10 g of deionized water to a reaction vessel, and stir evenly at room temperature to obtain a uniformly dispersed rosin acid solution;

[0102] S2. Add 20 g of soy protein isolate (SPI), 2.4 g of sodium dodecyl sulfonate and 100 g of deionized water to a reaction kettle and stir to disperse, forming a uniformly mixed material;

[0103] S3. Add 0.60 g of ammonium persulfate to the mixed material obtained in S2, and add sodium hydroxide to adjust the pH of the mixed material to 9. Carry out gelatinization reaction under stirring conditions to obtain a viscous liquid, that is, a gelatinized product. The temperature of the gelatinization reaction is 60 °C, and the time of the gelatinization reaction is 25 min;

[0104] S4. Add 0.1 g of epichlorohydrin and the rosin acid solution obtained in S1 to the gelatinized product obtained in S3, and carry out graft copolymerization reaction under stirring conditions. The temperature of the graft copolymerization reaction is 55 °C, and the time of the graft copolymerization reaction is 15 min. After the graft copolymerization reaction is completed, cool the obtained material to room temperature, add 0.4 g of dopamine hydrochloride, and stir and mix evenly to obtain an adhesive based on rosin acid graft copolymerized soy protein.

[0105] Example 9

[0106] As Figure 1 shown, a preparation method of an adhesive based on rosin acid graft copolymerized soy protein includes the following steps:

[0107] S1. Add 0.3 g of rosin acid particles, 0.3 g of hydroquinone, 8 g of absolute ethanol and 8 g of deionized water to a reaction vessel, and stir evenly at room temperature to obtain a uniformly dispersed rosin acid solution;

[0108] S2. Add 15 g of soy protein isolate (SPI), 1.8 g of sodium dodecyl sulfate, and 90 g of deionized water to a reaction kettle and stir to disperse, forming a uniformly mixed material.

[0109] S3. Add 0.45 g of ammonium persulfate to the mixed material obtained in S2, and add sodium hydroxide to adjust the pH of the mixed material to 9. Conduct a gelatinization reaction under stirring to obtain a viscous liquid, i.e., the gelatinized product. The temperature of the gelatinization reaction is 60 °C, and the time of the gelatinization reaction is 25 min.

[0110] S4. Add 0.1 g of epichlorohydrin and the rosin acid solution obtained in S1 to the gelatinized product obtained in S3, and conduct a graft copolymerization reaction under stirring. The temperature of the graft copolymerization reaction is 55 °C, and the time of the graft copolymerization reaction is 15 min. After the graft copolymerization reaction is completed, cool the obtained material to room temperature, add 0.1 g of dopamine hydrochloride, and stir to mix evenly to obtain an adhesive based on rosin acid graft copolymerized soy protein.

[0111] Example 10

[0112] As Figure 1 shown, a preparation method of an adhesive based on rosin acid graft copolymerized soy protein includes the following steps:

[0113] S1. Add 0.3 g of rosin acid particles, 0.3 g of hydroquinone, 8 g of absolute ethanol, and 8 g of deionized water to a reaction vessel, stir evenly at room temperature, and obtain a uniformly dispersed rosin acid solution.

[0114] S2. Add 15 g of soy protein isolate (SPI), 1.8 g of sodium dodecyl sulfate, and 90 g of deionized water to a reaction kettle and stir to disperse, forming a uniformly mixed material.

[0115] S3. Add 0.45 g of ammonium persulfate to the mixed material obtained in S2, and add sodium hydroxide to adjust the pH of the mixed material to 9. Conduct a gelatinization reaction under stirring to obtain a viscous liquid, i.e., the gelatinized product. The temperature of the gelatinization reaction is 60 °C, and the time of the gelatinization reaction is 25 min.

[0116] S4. Add 0.3 g of epichlorohydrin and the rosin acid solution obtained in S1 to the gelatinized product obtained in S3, and conduct a graft copolymerization reaction under stirring. The temperature of the graft copolymerization reaction is 55 °C, and the time of the graft copolymerization reaction is 15 min. After the graft copolymerization reaction is completed, cool the obtained material to room temperature, add 0.3 g of dopamine hydrochloride, and stir to mix evenly to obtain an adhesive based on rosin acid graft copolymerized soy protein.

[0117] Example 11

[0118] AsFigure 1 As shown in the figure, a preparation method of an adhesive based on rosin acid graft copolymerized soybean protein includes the following steps:

[0119] S1. Add 0.3 g of rosin acid particles, 0.3 g of hydroquinone, 8 g of absolute ethanol and 8 g of deionized water into a reaction vessel, stir evenly at room temperature to obtain a uniformly dispersed rosin acid solution;

[0120] S2. Add 15 g of soy protein isolate (SPI), 2.4 g of sodium dodecyl sulfonate and 90 g of deionized water into a reaction kettle and stir to disperse, forming a uniformly mixed mixture;

[0121] S3. Add 0.45 g of ammonium persulfate to the mixture obtained in S2, and add sodium hydroxide to adjust the pH of the mixture to 9. Carry out a gelatinization reaction under stirring conditions to obtain a viscous liquid, that is, a gelatinized product; the temperature of the gelatinization reaction is 60 °C, and the time of the gelatinization reaction is 25 min;

[0122] S4. Add 0.1 g of epichlorohydrin and the rosin acid solution obtained in S1 to the gelatinized product obtained in S3, and carry out a graft copolymerization reaction under stirring conditions. The temperature of the graft copolymerization reaction is 55 °C, and the time of the graft copolymerization reaction is 15 min. After the graft copolymerization reaction is completed, cool the obtained material to room temperature, add 0.3 g of dopamine hydrochloride, and stir and mix evenly to obtain an adhesive based on rosin acid graft copolymerized soybean protein.

[0123] Example 12

[0124] As Figure 1 shown in the figure, a preparation method of an adhesive based on rosin acid graft copolymerized soybean protein includes the following steps:

[0125] S1. Add 0.4 g of rosin acid particles, 0.4 g of hydroquinone, 10 g of absolute ethanol and 10 g of deionized water into a reaction vessel, stir evenly at room temperature to obtain a uniformly dispersed rosin acid solution;

[0126] S2. Add 15 g of soy protein isolate (SPI), 2.4 g of sodium dodecyl sulfonate and 100 g of deionized water into a reaction kettle and stir to disperse, forming a uniformly mixed mixture;

[0127] S3. Add 0.45 g of ammonium persulfate to the mixture obtained in S2, and add sodium hydroxide to adjust the pH of the mixture to 9. Carry out a gelatinization reaction under stirring conditions to obtain a viscous liquid, that is, a gelatinized product; the temperature of the gelatinization reaction is 60 °C, and the time of the gelatinization reaction is 25 min;

[0128] S4. Add 0.1 g of epichlorohydrin and the rosin acid solution obtained in S1 to the gelatinized product obtained in S3, and carry out graft copolymerization reaction under stirring conditions. The temperature of the graft copolymerization reaction is 55 °C, and the time of the graft copolymerization reaction is 15 min. After the graft copolymerization reaction is completed, cool the obtained material to room temperature, add 0.4 g of dopamine hydrochloride, and stir and mix evenly to obtain an adhesive based on rosin acid graft copolymerized soy protein.

[0129] Comparative Example 1

[0130] A preparation method of a conventional soy protein adhesive includes the following steps:

[0131] Add 20 g of soy protein isolate powder and 100 g of deionized water to a reaction kettle and stir and disperse to form a uniformly mixed material; carry out a reaction under stirring conditions; the temperature of the reaction is 65 °C, and the time of the reaction is 30 min to obtain a pure soy protein adhesive.

[0132] Comparative Example 2

[0133] A preparation method of a conventional soy protein-based aqueous adhesive includes the following steps:

[0134] Add 20 g of soy protein isolate powder, 2.4 g of sodium dodecyl sulfate and 100 g of deionized water to a reaction kettle and stir and disperse to form a uniformly mixed material; carry out a reaction under stirring conditions; the temperature of the reaction is 65 °C, and the time of the reaction is 30 min to obtain a soy protein-based adhesive.

[0135] Comparative Example 3

[0136] A preparation method of a conventional soy protein-based aqueous adhesive includes the following steps:

[0137] Add 20 g of soy protein isolate powder, 2.4 g of sodium dodecyl sulfate, 0.6 g of ammonium persulfate and 100 g of deionized water to a reaction kettle and stir and disperse to form a uniformly mixed material; carry out a reaction under stirring conditions; the temperature of the reaction is 65 °C, and the time of the reaction is 30 min to obtain a soy protein-based aqueous adhesive.

[0138] Comparative Example 4

[0139] A preparation method of a conventional soy protein adhesive includes the following steps:

[0140] Add 20 g of soy protein isolate powder, 2.4 g of sodium dodecyl sulfate, 0.6 g of ammonium persulfate, 0.1 g of epichlorohydrin and 100 g of deionized water to a reaction kettle and stir and disperse to form a uniformly mixed material; carry out a reaction under stirring conditions; the temperature of the reaction is 65 °C, and the time of the reaction is 30 min to obtain a soy protein-based aqueous adhesive.

[0141] Comparative Example 5

[0142] Poplar plywood was pressed using ordinary urea - formaldehyde resin (UF) adhesive. Under the conditions of a temperature of 35°C and a humidity of 85%, the mold growth time of the prepared adhesive was tested, and the results are shown in Table 1; poplar veneer with a specification of 40*40 cm 2 was used, with 24 g of adhesive applied on one side, a hot - pressing pressure of 1.0 MPa, a hot - pressing time of 4 min, and a hot - pressing temperature set at 120°C to prepare three - layer poplar plywood. The plywood bonding strength and water - resistant bonding strength are shown in Table 1. Samples were prepared using ordinary urea - formaldehyde resin adhesive according to the method of GB / T20284 - 2006, and the heat release in 600 s was tested. The total heat release THR in 600 s 600s The results are shown in Table 1.

[0143] Detection and analysis

[0144] The adhesives based on rosin - acid - grafted copolymerized soy protein prepared in Examples 1 to 5 and Examples 8 to 12 were respectively used for pressing poplar plywood. Under the conditions of a temperature of 35°C and a humidity of 85%, the mold growth time of the prepared adhesive was tested, and the results are shown in Table 1; poplar veneer with a specification of 40*40 cm 2 was used, with 24 g of adhesive applied on one side, a hot - pressing pressure of 1.0 MPa, a hot - pressing time of 4 min, and a hot - pressing temperature set at 120°C to prepare three - layer poplar plywood. The plywood bonding strength and water - resistant bonding strength are shown in Table 1. Samples were prepared using the prepared adhesive according to the method of GB / T 20284 - 2006, and the heat release in 600 s and the total heat release THR in 600 s were tested 600s The results are shown in Table 1.

[0145] The adhesives based on rosin - acid - grafted copolymerized soy protein prepared in Examples 6 and 7 were respectively used for pressing poplar plywood. Under the conditions of a temperature of 35°C and a humidity of 85%, the mold growth time of the prepared adhesive was tested, and the results are shown in Table 1; poplar veneer with a specification of 40*40 cm 2 was used, with 24 g of adhesive applied on one side, a hot - pressing pressure of 1.0 MPa, a hot - pressing time of 4 min, and a hot - pressing temperature set at 140°C to prepare three - layer poplar plywood. The plywood bonding strength and water - resistant bonding strength are shown in Table 1. Samples were prepared using the prepared adhesive according to the method of GB / T 20284 - 2006, and the heat release in 600 s and the total heat release THR in 600 s were tested 600s The results are shown in Table 1.

[0146] Use the pure soy protein adhesive prepared in Comparative Example 1 to press poplar plywood. Under the conditions of a temperature of 35 °C and a humidity of 85%, test the mold growth time of the prepared adhesive, and the results are shown in Table 1; use poplar veneer with a specification of 40*40 cm 2 , apply 24 g of adhesive on one side, the hot pressing pressure is 1.0 MPa, the hot pressing time is 4 min, and the hot pressing temperature is set at 120 °C to prepare three-layer poplar plywood. The bonding strength and water-resistant bonding strength of the plywood are shown in Table 1. Use the prepared adhesive to prepare samples according to the method of GB / T 20284-2006, and test the heat release for 600 s. The total heat release THR in 600 s 600s The results are shown in Table 1.

[0147] Use the soy protein-based waterborne adhesive prepared in Comparative Example 3 to press poplar plywood. Under the conditions of a temperature of 35 °C and a humidity of 85%, test the mold growth time of the prepared adhesive, and the results are shown in Table 1; use poplar veneer with a specification of 40*40 cm 2 , apply 24 g of adhesive on one side, the hot pressing pressure is 1.0 MPa, the hot pressing time is 4 min, and the hot pressing temperature is set at 120 °C to prepare three-layer poplar plywood. The bonding strength and water-resistant bonding strength of the plywood are shown in Table 1. Use the prepared adhesive to prepare samples according to the method of GB / T 20284-2006, and test the heat release for 600 s. The total heat release THR in 600 s 600s The results are shown in Table 1.

[0148] Table 1 Properties of the adhesives prepared in Examples 1 to 12 and Comparative Examples 1 to 5 and performance indicators of the prepared wood-based panels

[0149]

[0150]

[0151] Note: The national standards in the table are: GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorated Wood-based Panels", GB8624-2012 "Classification of Combustion Performance of Building Materials and Products", GB / T39600-2021 "Formaldehyde Emission Classification of Wood-based Panels and Their Products", and the listed indicators are the differential indicators that can be affected by the change of the adhesive.

[0152] As can be seen from the data in Table 1 above, the adhesives based on rosin acid graft copolymerized soy protein obtained by Examples 1 to 12 of the present invention have good properties, and the various differential indexes of mildew resistance and dry and wet gluing strength performance of wood-based panels have reached or exceeded the relevant technical index requirements specified in the national standard GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorated Wood-based Panels". The differential index of flame retardant performance has reached or exceeded Class B1 in the national standard GB8624-2012 "Classification of Combustion Performance of Building Materials and Products", and the differential index of formaldehyde release has reached or exceeded E NF level in the national standard GB / T39600-2021 "Formaldehyde Release Classification of Wood-based Panels and Their Products". Among them, the dry and wet gluing strength of the adhesive based on rosin acid graft copolymerized soy protein obtained in Example 3 for bonding wood-based panels is the best. In Comparative Example 5, the use of ordinary urea-formaldehyde resin (UF) makes the dry gluing strength of wood-based panels excellent, but due to the presence of moisture, its bonding effect is weakened, resulting in a lower wet gluing strength, indicating that ordinary urea-formaldehyde resin (UF) is poor in water resistance. In addition, due to the large amount of formaldehyde contained in traditional urea-formaldehyde resin, its formaldehyde release is very high. In Comparative Example 1, due to the use of only a single soy protein powder, the structure of the protein could not be effectively changed, and the crosslinking effect was poor. Eventually, the prepared adhesive mildewed within one day, and the dry and wet gluing strengths of wood-based panels were both low. In Comparative Examples 2 to 4, although the addition of a small amount of anionic surfactant and initiator effectively changed the structure of soy protein, the prepared adhesive had poor mildew resistance. The dry gluing strength of the wood-based panel prepared with this adhesive was improved, but the wet gluing strength was low, and the flame retardant performance was also poor.

[0153] The adhesives based on rosin acid graft copolymerized soy protein prepared in Examples 1 to 5 were respectively pressed with metal and glass sheets. The metal sheet had a specification of 40*40 cm 2 , with 24 g of glue applied on one side, a hot pressing pressure of 1.0 MPa, a hot pressing time of 4 min, and a hot pressing temperature set at 120 °C to prepare a metal plate lap joint; the glass single plate had a specification of 40*40 cm 2 , with 24 g of glue applied on one side, a hot pressing pressure of 1.0 MPa, a hot pressing time of 4 min, and a hot pressing temperature set at 70 °C to prepare a glass plate lap joint. Lap joint tests were carried out between the same matrix materials and different matrix materials, and the lap joint schematic diagram is as Figure 2 shown.

[0154] Figure 2Among them, from left to right are the lap joint tests of glass-to-glass using the adhesive prepared in Example 1, the lap joint tests of zinc sheet-to-zinc sheet using the adhesive prepared in Example 2, the lap joint tests of steel sheet-to-steel sheet using the adhesive prepared in Example 3, the lap joint tests of poplar plywood-to-poplar plywood using the adhesive prepared in Example 4, and the lap joint tests of poplar plywood-to-zinc sheet using the adhesive prepared in Example 5.

[0155] From Figure 2 It can be analyzed from this that the adhesives prepared in Examples 1 to 5 can all be applied to the bonding between the same matrix and different matrices, and the prepared samples will not fall off during the process of being lifted and shaken at any height. It shows that a large number of covalent bond interactions are formed between the components of the prepared adhesive with a complex network structure, having high bonding performance and can be applied to a variety of different bonding environments.

[0156] Use the adhesive prepared in Example 3 to bond glass veneers (25mm * 25mm), and then conduct a knock-down test on the glass plate bonded with the adhesive prepared in Example 3 at a vertical height of 30 cm and tap the side of the glass plate to evaluate the bonding strength of the glass plate. The results are as Figure 3 shown.

[0157] From Figure 3 It can be analyzed from this that when the prepared glass plate is subjected to a high-altitude knock-down and side-tap shock test at a vertical height of 30 cm, the glass plate does not break or fracture. This shows that the prepared adhesive has a stable cross-linked structure and forms a stable bonding effect with the surface of the glass veneer, making the prepared glass plate exhibit stable performance in the high-altitude drop and side-tap tests. Secondly, the stable bonding effect generated enables the prepared glass plate to still have stable mechanical properties after being placed for a long time.

[0158] 2) Fourier transform infrared spectroscopy (FTIR) analysis

[0159] Perform Fourier transform infrared spectroscopy (FTIR) analysis on the adhesive samples prepared in Example 3, Comparative Example 1, and Comparative Example 2 on a Varian 1000, and the scanning range is 500 - 4000 cm -1 . The measurement method is to evenly spread the liquid sample on a KBr sheet, and thoroughly grind the dried solid sample and cured resin with KBr solid for determination. The results are as Figure 4 shown.

[0160] From Figure 4 It can be analyzed from this that the typical absorption peaks of soy protein isolate (Comparative Example 1) appear at 3282, 2923, 1629, 1530, 1233 cm -1At this point, it corresponds to the N-H / O-H stretching vibration of free radicals in soy protein isolate (SPI), the C-H stretching vibration of methylene, the C=O bending vibration of amide I, the N-H deformation vibration of amide II, and the C-N stretching vibration of amide III. Compared with the soy protein adhesive of Comparative Example 1, the modified SPI-based adhesive (Example 3) has an enhanced O-H stretching vibration peak at 3282 cm -1 This is because the addition of an anionic surfactant and rosin acid forms a physical cross-linked structure with soy protein isolate through chemical bonds and hydrogen bonds. In addition to the obvious change at 3282 cm -1 for the adhesive prepared in Example 3, the peak at 2842 cm -1 is significantly enhanced. This is the characteristic peak of the hydrogenated phenanthrene ring in rosin acid, indicating that rosin acid has reacted sufficiently with soy protein isolate and has been successfully grafted onto soy protein isolate. The characteristic peaks of amide groups were detected in Example 3 and Comparative Examples 1 and 2. In addition to the specific groups, the C=O vibration peak of the carboxyl group in rosin acid was detected at 1736 cm -1 for the adhesive prepared in Example 3, which also indicates that rosin acid has been successfully added to the prepared adhesive. In addition, from Figure 2 it was also obtained that the adhesive prepared in Example 3 has rich functional groups. The addition of rosin acid undergoes a graft copolymerization reaction with soy protein isolate to form a relatively complex cross-linked hybrid network structure, thereby enhancing the bonding performance and water resistance of the adhesive.

[0161] 3) Thermogravimetric curve (TG) and derivative thermogravimetric curve (DTG) analysis

[0162] The samples of the adhesives prepared in Examples 1 to 4, Comparative Example 1, and Comparative Example 2 were analyzed by thermogravimetric curve (TG) and derivative thermogravimetric curve (DTG). The analysis was carried out on a thermogravimetric analyzer (TGA, ZCT-A, China). In the range of 25-500 °C, the degradation process of the sample (5.0 mg) was detected at a heating rate of 10 °C / min to measure the thermal degradation of the soy protein-based adhesive powder (200 mesh). The measurement method was to grind the prepared adhesive into a 200-mesh powder and place it in an alumina crucible for testing. The results are as Figure 5 shown.

[0163] From Figure 5Comprehensive analysis shows that in the thermogravimetric curve (TG), the residual mass of Comparative Example 1 and Comparative Example 2 at 480 °C is relatively low, only 23.7%; after the addition of rosin acid and soy protein isolate for graft copolymerization, the residual mass of Example 3 increased to 42.8%. This is because the addition of rosin acid causes a reaction between it and soy protein isolate to form a dense and complex network structure, shielding the contact with oxygen, thereby increasing the heat resistance of the adhesive; at the same time, the formed network cross-linked structure contains a large number of stable covalent bonds, resulting in a higher temperature required for thermal decomposition, thus leading to a higher residual mass. It can also be seen from the derivative thermogravimetric curve (DTG) that compared with Comparative Example 1 and Comparative Example 2, the degradation rate in the second stage of Examples 1 to 4 has a significant decrease, and the degradation temperature also has a certain increase. The degradation in the second stage is mainly related to the breakage of the main chain of the adhesive, which also indicates that the addition of rosin acid and dopamine hydrochloride makes the adhesive form a more stable structure, thereby reducing the total heat release (THR). 600s This further proves that the adhesive of the present invention has excellent flame retardant properties.

[0164] In summary, the adhesive based on rosin acid graft copolymerized soy protein of the present invention is suitable for the bonding of wood-based panels, metals and glass. First, the soy protein isolate and rosin acid used are both natural products, having the characteristics of non-toxic side effects and biodegradability, thus effectively solving the environmental pollution problem caused during the manufacturing process of the adhesive. Second, by blending soy protein isolate with an anionic surfactant and heating to dissolve, the helical structure of soy protein isolate can be changed, enhancing the degree of cross-linking reaction, thereby improving the bonding effect of the water-based adhesive. In addition, after adding epichlorohydrin and rosin acid, the hydrolysis-coupling grafting effect between the cross-linking agent formed by their reaction and soy protein isolate significantly improves the water resistance, mildew resistance and flame retardant properties of the water-based adhesive after curing. At the same time, the addition of dopamine hydrochloride further undergoes a Michael addition reaction with the adhesive to form a dense cross-linked network structure, thereby further increasing the various properties of the adhesive.

[0165] The water-based adhesive prepared by the present invention is a water-based slurry type coating, which can be directly used after long-term storage, overcoming the problems of poor water retention and short storage time of traditional aldehyde-based adhesives and pure soy protein adhesives, and solving the problems of harmfulness and difficult recycling of traditional hot-pressing adhesives. At the same time, this method saves energy, the process operation is more convenient, and it does not add, generate or release any toxic and harmful substances, having higher industrial production value.

[0166] The above embodiments are only the preferred embodiments of the present invention, and the protection scope is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the protection scope of the present invention.

Claims

1. An adhesive based on rosin acid grafted copolymerized soybean protein, characterized in that: Ingredients include: Soy protein isolate, anionic surfactant, initiator, epichlorohydrin, rosin acid, dopamine hydrochloride and water.

2. The adhesive based on rosin acid graft copolymerized soybean protein according to claim 1, characterized in that: The invention comprises the following raw materials in parts by weight: 10 to 20 parts by weight of soy protein isolate, 1 to 3 parts by weight of anionic surfactant, 0.1 to 0.9 parts by weight of initiator, 0.05 to 2 parts by weight of epichlorohydrin, 0.05 to 0.6 parts by weight of rosin acid, 0.1 to 0.5 parts by weight of dopamine hydrochloride and 75 to 100 parts by weight of water.

3. The adhesive based on rosin acid graft copolymerized soybean protein according to claim 2, characterized in that: The invention comprises the following raw materials in parts by weight: 10 to 15 parts by weight of soy protein isolate, 1.8 to 2 parts by weight of anionic surfactant, 0.6 parts by weight of initiator, 0.05 to 1.5 parts by weight of epichlorohydrin, 0.2 to 0.4 parts by weight of rosin acid, 0.1 to 0.3 parts by weight of dopamine hydrochloride and 85 parts by weight of water.

4. The adhesive based on rosin acid graft copolymerized soybean protein according to claim 3, characterized in that: The invention comprises the following raw materials by weight: 15 parts by weight of soy protein isolate, 1.8 parts by weight of anionic surfactant, 0.6 parts by weight of initiator, 0.1 parts by weight of epichlorohydrin, 0.3 parts by weight of rosin acid, 0.1 parts by weight of dopamine hydrochloride and 85 parts by weight of water.

5. The adhesive based on rosin acid graft copolymerized soybean protein according to claim 1, characterized in that: The soy protein isolate is selected from soy protein isolate powder; and / or, the initiator is selected from ammonium persulfate; And / or, the anionic surfactant is selected from one or two of sodium N-acylaminocarboxylate, sodium dodecyl sulfonate and sodium dodecyl sulfate; And / or, the solid content of the rosin acid solution is 40-60wt%.

6. A method for preparing an adhesive based on rosin acid graft copolymerized soybean protein according to any one of claims 1 to 5, characterized in that: The following steps are involved: Mixing rosin acid, an alcohol solvent, hydroquinone and water to obtain a rosin acid solution; Mixing soy protein isolate, anionic surfactant and water to obtain a mixed material; Adding an initiator to the mixed material, adjusting the pH of the mixed material to be alkaline, and performing a gelatinization reaction to obtain a gelatinized product; Epichlorohydrin and the rosin acid solution are added to the gelatinized product to carry out graft copolymerization reaction, and dopamine hydrochloride is added after cooling to obtain an adhesive based on rosin acid graft copolymerized soybean protein.

7. The preparation method according to claim 6, characterized in that: The temperature of the gelatinization reaction is 60-65°C; And / or, the gelatinization reaction time is 20 to 35 minutes; and / or, the temperature of the graft copolymerization reaction is 55-65° C.; And / or, the graft copolymerization reaction time is 10 to 25 minutes.

8. The preparation method according to claim 6, characterized in that: Using alkali to adjust the pH of the mixture to 9-10; And / or, the alcohol solvent is selected from at least one of methanol, ethanol or propanol; And / or, after cooling to room temperature, adding dopamine hydrochloride, stirring and mixing evenly, to obtain an adhesive based on rosin acid grafted copolymerized soybean protein.

9. An application of an adhesive based on rosin acid graft copolymerized soybean protein according to any one of claims 1 to 5, characterized in that: The soy protein-based water-based adhesive can be applied to artificial boards, metals and glass materials.

10. The use according to claim 9, characterized in that: When the adhesive based on rosin acid graft copolymerized soybean protein is used to bond artificial boards, the hot pressing temperature is 120-200° C.; And / or, when the soy protein-based water-based adhesive is used to bond metals, the hot pressing temperature is 90-130° C.; And / or, when the soy protein-based water-based adhesive is used to bond glass, the hot pressing temperature is 55-80°C.

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