A protein adhesive, its preparation method and use

Abstract

This invention discloses a protein adhesive, its preparation method, and its application. The preparation method includes the following steps: S1, mixing protein from cake meal, alkali, and water to react in reaction I to obtain intermediate I; mixing nano-inorganic minerals, bis-(3-(triethoxysilane)propyl)-tetrasulfide, and water to react in reaction II, followed by solid-liquid separation to obtain intermediate II; S2, mixing intermediate I, intermediate II, polyaziridine polymer, and 4-dimethylaminopyridine to react in reaction III to obtain intermediate III; S3, mixing intermediate III, sulfur, and a surfactant to obtain the protein adhesive. The protein adhesive prepared by the method of this invention exhibits high mechanical properties, flame retardant properties, and water resistance.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to a protein adhesive, its preparation method, and its application. Background Technology

[0002] The timber industry uses large quantities of formaldehyde adhesives; however, formaldehyde adhesives and the wood products they produce release volatile harmful substances such as formaldehyde during production and use. To avoid using formaldehyde adhesives, alternatives have been sought. In recent years, protein adhesives have emerged as a natural and green material that can self-degrade under environmental conditions, thus not burdening the ecosystem. However, protein adhesives suffer from several defects in their protein structure, including low bonding strength and poor water resistance, which prevent them from meeting product strength requirements. Furthermore, their high viscosity makes them difficult to apply, limiting their application in the timber industry.

[0003] Therefore, it is necessary to develop a new method for preparing protein-based adhesives. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the first aspect of the present invention proposes a method for preparing a protein adhesive, wherein the protein-based adhesive prepared by the method has good water resistance, good flame retardancy, and good mechanical properties.

[0005] A second aspect of the present invention also provides a protein adhesive.

[0006] A third aspect of the present invention also provides an application of a protein adhesive.

[0007] A method for preparing a protein adhesive according to a first aspect of the present invention includes the following steps:

[0008] S1. Mix the separated protein from the cake meal, alkali, and water to react in reaction I to obtain intermediate I; mix the nano-inorganic minerals, bis-(3-(triethoxysilane)propyl)-tetrasulfide, and water to react in reaction II, and then separate the solid and liquid phases to obtain intermediate II;

[0009] S2. Intermediate I, intermediate II, polyaziridine polymer and 4-dimethylaminopyridine are mixed and reacted in reaction III to obtain intermediate III;

[0010] S3. Mix intermediate III, sulfur, and surfactant to obtain a protein adhesive.

[0011] The method for preparing the protein adhesive according to embodiments of the present invention has at least the following beneficial effects:

[0012] The protein adhesive prepared by the method of this invention exhibits high mechanical properties, flame retardant properties, and water resistance. This invention first degrades protein isolate from oilseed cake to obtain intermediate I, then modifies it with nano-inorganic minerals. Polyaziridine polymers are modified onto intermediates I and II, and the active groups (aziridine ring groups) on these intermediates undergo a polymerization reaction with sulfur, forming a polymeric network structure with cross-links between intermediates I, between protein and intermediate II, and between intermediates II. Thus, a protein adhesive with excellent mechanical, flame retardant, and water resistance properties can be obtained.

[0013] According to a preferred embodiment of the present invention, the nano-inorganic mineral includes at least one of nano-montmorillonite, nano-palmitite, nano-boehmite, or nano-kaolinite.

[0014] According to a preferred embodiment of the present invention, the oilseed cake protein isolate includes at least one of tung oil oilseed cake protein isolate, camellia oilseed cake protein isolate, soybean oilseed cake protein isolate, and litsea cubeba oilseed cake protein isolate.

[0015] According to a preferred embodiment of the present invention, the protein isolate from the oilseed cake accounts for 15% to 25% of the total mass, calculated based on the total mass of the protein isolate, alkali, and water.

[0016] According to a preferred embodiment of the present invention, the alkali accounts for 0.5% to 3% of the total mass of the protein isolate, alkali and water in the cake meal.

[0017] According to a preferred embodiment of the present invention, the alkali is selected from at least one of urea, sodium hydroxide, and potassium hydroxide.

[0018] According to a preferred embodiment of the present invention, the nano-inorganic minerals account for 3% to 8% of the total mass of the nano-inorganic minerals, bis-(3-(triethoxysilane)propyl)-tetrasulfide, and water.

[0019] According to a preferred embodiment of the present invention, the bis-(3-(triethoxysilane)propyl)-tetrasulfide accounts for 10% to 25% of the total mass of the nano-inorganic mineral, bis-(3-(triethoxysilane)propyl)-tetrasulfide, and water.

[0020] According to a preferred embodiment of the present invention, the temperature of reaction II is 60–80°C.

[0021] According to a preferred embodiment of the present invention, the reaction time of reaction II is 30 to 50 minutes.

[0022] According to a preferred embodiment of the present invention, the amount of intermediate II is 0.5% to 2% based on the total mass of the protein isolate, alkali and water in the meal.

[0023] According to a preferred embodiment of the present invention, the amount of the polyaziridine polymer used is 5% to 12% based on the total mass of the separated protein, alkali and water in the cake meal.

[0024] According to a preferred embodiment of the present invention, the amount of 4-dimethylaminopyridine used is 0.01% to 0.5% based on the total mass of the separated protein, alkali and water in the cake meal.

[0025] According to a preferred embodiment of the present invention, the temperature of reaction III is 60–80°C.

[0026] According to a preferred embodiment of the present invention, the reaction time of reaction III is 1h to 2h.

[0027] According to a preferred embodiment of the present invention, the amount of sulfur used is 1.5% to 5% based on the total mass of the separated protein, alkali and water in the cake meal.

[0028] According to a preferred embodiment of the present invention, the amount of surfactant used is 0.5% to 2% based on the total mass of the separated protein, alkali and water in the cake meal.

[0029] According to a preferred embodiment of the present invention, the surfactant is selected from at least one of sodium dodecyl sulfate, quaternary ammonium salt, or sodium dodecylbenzenesulfonate. This promotes sulfur dispersion.

[0030] According to a preferred embodiment of the present invention, the sulfur has a particle size of ≤74μm.

[0031] A second aspect of the present invention provides a protein adhesive prepared by the preparation method described in the first aspect of the present invention.

[0032] A third aspect of the present invention provides the application of a protein adhesive prepared by the preparation method described in the first aspect of the present invention in the preparation of sheet materials.

[0033] According to a preferred embodiment of the present invention, the board material includes bamboo-wood composite engineered wood panel, bamboo-wood fiberboard, particleboard, and plywood.

[0034] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Detailed Implementation

[0035] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0036] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0037] The raw materials used in the embodiments and comparative examples of this invention are as follows:

[0038] Camellia oil cake protein, soybean cake protein isolate, and nano-inorganic minerals: nano-montmorillonite and nano-palmitite; purchased from Maclean's Reagent Network.

[0039] Bis-(3-(triethoxysilane)propyl)-tetrasulfide, urea, sulfur, 4-dimethylaminopyridine, polyaziridine polymer, surfactant: sodium dodecyl sulfate; all purchased from Xilong Chemical and Sinopharm Chemical Reagent Co., Ltd.

[0040] Example 1

[0041] This example provides a protein adhesive, the preparation method of which is as follows:

[0042] S1. 20g of camellia seed cake protein, 2g of urea, and 78g of water were mixed and stirred continuously for 30 minutes until the protein was completely dissolved to obtain intermediate I. 8g of nano-montmorillonite, 20g of bis-(3-(triethoxysilane)propyl)-tetrasulfide, and 72g of water were mixed in a specific ratio and stirred continuously at 80℃ for 40 minutes. After cooling, the product was filtered, washed with water, and vacuum dried to obtain intermediate II.

[0043] S2. 5% of intermediate II is blended with intermediate I, and then 10% of polyaziridinium polymer and 0.2% of 4-dimethylaminopyridine are added and stirred until homogeneous. The blend is then reacted under reflux (60°C) for 2 hours to obtain intermediate III.

[0044] S3. Grind the sulfur through a 200-mesh sieve, and add 2% sulfur and 1% sodium dodecyl sulfate to intermediate III to obtain a protein adhesive.

[0045] Example 2

[0046] This example provides a protein adhesive, which is prepared in the same way as in Example 1, except that soybean meal protein isolate is used instead of camellia meal protein.

[0047] Example 3

[0048] This example provides a protein adhesive, which is prepared in the same way as in Example 1, except that, based on the total mass of nano-inorganic minerals, bis-(3-(triethoxysilane)propyl)-tetrasulfide and water, bis-(3-(triethoxysilane)propyl)-tetrasulfide accounts for 10% of the total mass.

[0049] Example 4

[0050] This example provides a protein adhesive, which is prepared in the same way as in Example 1, except that the amount of polyaziridine polymer used is 5% based on the total mass of the separated protein, alkali and water from the cake meal.

[0051] Example 5

[0052] This example provides a protein adhesive, which is prepared in the same way as in Example 1, except that the amount of sulfur used is 5% based on the total mass of the separated protein, alkali and water from the cake meal.

[0053] Example 6

[0054] This example provides a protein adhesive, which is prepared in the same way as in Example 1, except that nano-pastreak is used instead of nano-montmorillonite.

[0055] Comparative Example 1

[0056] This example provides a protein adhesive, which is prepared in the same way as in Example 1, except that nano-montmorillonite is not used in step S1.

[0057] Comparative Example 2

[0058] This example provides a protein adhesive, which is prepared in the same way as in Example 1, except that in step S1, bis-(3-(triethoxysilane)propyl)-tetrasulfide is not present.

[0059] Comparative Example 3

[0060] This example provides a protein adhesive, which is prepared in the same way as in Example 1, except that in step S1, γ-mercaptopropyltrimethoxysilane (KH590) is used instead of bis-(3-(triethoxysilane)propyl)-tetrasulfide.

[0061] Comparative Example 4

[0062] This example provides a protein adhesive, which is prepared in the same way as in Example 1, except that polyaziridine polymer is not added in step S2.

[0063] Comparative Example 5

[0064] This example provides a protein adhesive, which is prepared in the same way as in Example 1, except that sulfur is not added in step S3.

[0065] Performance testing

[0066] Thin wood shavings are used to make boards with a thickness of 6 mm. The raw material consists of wood shavings with a length of 0.8 to 4 mm, an aspect ratio of 15 mm, and a thickness of 0.2 to 0.25 mm.

[0067] The protein adhesives of the embodiments and comparative examples of this invention were used to prepare thin bamboo and wood particleboard (bamboo shavings). The specific process is as follows: Using a thickness gauge with a thickness of 6 mm, a board with dimensions of 600 mm × 600 mm × 6 mm was prepared for testing using the flat pressing method. Hot pressing process conditions: hot pressing temperature 125℃, hot pressing time 280 s, hot pressing pressure 1.2 MPa, adhesive application rate 12%.

[0068] The prepared thin bamboo particleboard was subjected to the following tests, and the results are shown in Table 1:

[0069] Internal bond strength, static bending strength, elastic modulus, 2-hour water absorption thickness swelling rate, and limiting oxygen index: tested according to T / CNFPIA3013-2021.

[0070] Table 1

[0071]

[0072] As can be seen from the data in Table 1, the protein adhesives prepared in Examples 1 to 6 of the present invention have high mechanical properties, water resistance and flame retardant properties.

[0073] In Comparative Example 1, since no nano-montmorillonite was added, only the autogenous hydrolysis reaction of bis-(3-(triethoxysilane)propyl)-tetrasulfide occurred in step S1. Without nano-montmorillonite as a substrate, although the product obtained had a certain degree of reactivity, the board obtained after curing had poor mechanical properties due to the lack of nano-montmorillonite characteristics, and there was no improvement in flame retardant properties.

[0074] In Comparative Example 2, no bis-(3-(triethoxysilane)propyl)-tetrasulfide was added. In step S1, the surface of the nano-montmorillonite could not be modified with the required reactive groups, resulting in only simple blending with the emulsion system. It could not participate in subsequent synthesis and thermosetting reactions. The weak reactivity of each substance and the inability to form covalent bonds between components led to poor physical and mechanical properties. Furthermore, the simple blending of nano-montmorillonite resulted in easy aggregation and sedimentation in the emulsion, preventing uniform distribution within the board and thus no significant improvement in flame retardant performance.

[0075] In Comparative Example 3, γ-mercaptopropyltrimethoxysilane (KH590) replaced bis-(3-(triethoxysilane)propyl)-tetrasulfide. Although KH590 is also a silane coupling agent capable of hydrolytic modification on the surface of nano-montmorillonite, its structure differs significantly from that of bis-(3-(triethoxysilane)propyl)-tetrasulfide. While both can modify thiol groups, their reactivity differs significantly. After replacement with KH590, the modified nano-montmorillonite showed weaker reactivity with subsequent components, failing to form effective covalent bonds, resulting in poor physical and mechanical properties of the board. It also caused heterogeneous blending of the components, leading to sedimentation and a concentrated, uneven distribution of nano-montmorillonite within the board, resulting in no significant improvement in flame retardant performance.

[0076] In Comparative Example 4, no polyaziridine polymer was added. In step S2, the surface of the nano-montmorillonite could not be modified with the required reactive groups, meaning it could not participate in the reaction with the sulfur monomer in step S3. The substances in S3 were simply blended, resulting in weak reactivity and an inability to covalently bond with themselves or protein macromolecules, leading to poor physical and mechanical properties of the molded board. Furthermore, the nano-montmorillonite also failed to participate in the reaction in step S3. The simple blending of components easily led to aggregation and sedimentation in the emulsion, preventing uniform distribution within the board and resulting in no significant improvement in flame retardant performance.

[0077] In Comparative Example 5, no sulfur was added. Sulfur is a crucial component in the thermosetting reaction of modified protein-based bamboo and wood adhesives. The dispersion of sulfur monomer powder in the adhesive emulsion system allows the active groups on the surface of the modified nanoparticles to react with sulfur, forming stable covalent bonds and enabling the overall reaction. Because no sulfur was added in Comparative Example 5, the reactivity of each component in the final thermosetting reaction was weak, resulting in poor physical and mechanical properties of the resulting board. Furthermore, nano-montmorillonite could not participate in the reaction in step S3, leading to simple mixing of components. This resulted in easy aggregation and sedimentation in the emulsion, preventing uniform distribution within the board and thus no significant improvement in flame retardant performance.

[0078] The present invention has been described in detail above with reference to the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing a protein adhesive, characterized by, The method comprises the following steps: S1, mixing the cake separated protein, alkali and water to carry out reaction I to obtain intermediate I; mixing the nano inorganic mineral, bis-(3-(triethoxysilyl) propyl)-tetrasulfide and water to carry out reaction II, and carrying out solid-liquid separation to obtain intermediate II; S2, mixing the intermediate I, intermediate II, polyaziridine polymer and 4-dimethylamino pyridine to carry out reaction III to obtain intermediate III; S3, mixing the intermediate III, sulfur and surfactant to obtain the protein adhesive; The cake separated protein accounts for 15% to 25% of the total mass of the cake separated protein, alkali and water; The amount of the intermediate II accounts for 0.5% to 2% of the total mass of the cake separated protein, alkali and water; The amount of the polyaziridine polymer accounts for 5% to 12% of the total mass of the cake separated protein, alkali and water; The amount of the 4-dimethylamino pyridine accounts for 0.01% to 0.5% of the total mass of the cake separated protein, alkali and water; The amount of the sulfur accounts for 1.5% to 5% of the total mass of the cake separated protein, alkali and water.

2. The method of claim 1, wherein the protein adhesive is prepared by the steps of: The nano inorganic mineral comprises at least one of nano montmorillonite, nano palygorskite, nano boehmite or nano kaolin.

3. The method of claim 1, wherein the protein adhesive is prepared by the steps of: The nano inorganic mineral accounts for 3% to 8% of the total mass of the nano inorganic mineral, bis-(3-(triethoxysilyl) propyl)-tetrasulfide and water.

4. The method of claim 1, wherein the protein adhesive is prepared by the steps of: The temperature of the reaction II is 60 to 80℃.

5. The method of claim 1, wherein the protein adhesive is prepared by the steps of: The temperature of the reaction III is 60 to 80℃.

6. A protein adhesive, characterized by, Prepared by the preparation method in any one of claims 1 to 5.

7. Application of the protein adhesive prepared by the preparation method in any one of claims 1 to 5 in preparing a plate.

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