Rosin derivative modified soybean protein adhesive and preparation method thereof

Abstract

The invention discloses a rosin derivative modified soybean protein adhesive and a preparation method thereof, the rosin derivative modified soybean protein adhesive comprises the following raw materials: 40 parts of a thermally alkalized soybean protein adhesive, 1.5-2.0 parts of a cyclic carbonated rosin derivative, 0.5-1.0 part of microcrystalline cellulose, and 0.3-0.5 part of calcium chloride; the parts are parts by mass; the preparation method of the thermally alkalized soybean protein adhesive comprises the following steps: dissolving urea and sodium hydroxide in deionized water, adding soybean protein isolate into the solution, heating, continuously stirring and reacting for a certain time to obtain the thermally alkalized soybean protein adhesive. The soybean protein adhesive is modified through multiple cross-linking reactions among the rosin derivative, cellulose, calcium chloride and soybean protein molecules, a compact cross-linked network is formed, the bonding performance of the soybean protein adhesive is effectively improved, and the waterproof performance of the soybean protein adhesive is improved; meanwhile, the curing time is effectively shortened.

Description

Technical Field

[0001] This invention relates to a rosin derivative modified soybean protein adhesive and its preparation method, belonging to the field of novel biomass adhesives. Background Technology

[0002] In recent years, the market consumption of wood adhesives has continued to grow. Currently, mainstream products such as phenolic resin (PF), urea-formaldehyde resin (UF), and melamine-formaldehyde resin (MF) not only rely on limited petroleum resources, but also pose significant hazards to human health and the environment during their production and use.

[0003] Soy protein adhesives, as a natural biomass adhesive, are mainly derived from soybean meal or soybean flour. They offer advantages such as being environmentally friendly, renewable, and non-petroleum-dependent, and have been widely used in the field of engineered wood products. However, in practical applications, soybean protein adhesives suffer from insufficient bonding strength and poor water resistance. Furthermore, due to the tendency of soybean protein to agglomerate and the poor flowability of the adhesive, large amounts of water are often required to maintain operability in industrial production. This directly leads to longer hot-pressing times, reduced production efficiency, and high energy costs, which are key issues restricting the widespread application of soybean protein adhesives. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a rosin derivative-modified soybean protein adhesive and its preparation method, thereby solving the problems of low bonding strength, poor water resistance, and poor flowability of existing soybean protein adhesives.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A rosin derivative modified soybean protein adhesive, comprising: 40 parts of heat-alkalized soybean protein adhesive, 1.5-2.0 parts of cyclic carbonated rosin derivative, 0.5-1.0 parts of microcrystalline cellulose, and 0.3-0.5 parts of calcium chloride; wherein the parts are by weight.

[0007] The preparation method of the thermally alkalized soybean protein adhesive is as follows: urea and sodium hydroxide are dissolved in deionized water, soybean protein isolate is added to the solution, and the mixture is heated and stirred continuously for a certain period of time to obtain the thermally alkalized soybean protein adhesive.

[0008] The structure of the cyclic carbonated rosin derivative is as follows:

[0009]

[0010] This invention modifies soybean protein adhesives through multiple cross-linking reactions between rosin derivatives, cellulose, calcium chloride, and soybean protein molecules, forming a dense cross-linked network that effectively improves the adhesive's bonding performance and waterproofing properties. Simultaneously, the hot-pressing process of the adhesive is optimized by thermal alkalization pretreatment of soybean protein and the construction of the coordination bond network, effectively reducing the curing time. The rosin derivative-modified soybean protein adhesive prepared by this invention has the advantages of using environmentally friendly raw materials with no harmful gas emissions, and solves the problems of poor adhesion, water resistance, and long curing time of existing soybean protein adhesives.

[0011] To improve the modification effect, the mass ratio of soy protein isolate, urea, sodium hydroxide and deionized water in the preparation of the thermally alkalized soybean protein adhesive is 5:(9-11):(3.5-4.5):(14-16).

[0012] To ensure the modification effect, the reaction temperature for the thermally alkalized soybean protein adhesive is 50-60℃ and the reaction time is 20-30 minutes.

[0013] To further improve the quality of the adhesive, the purity of the above-mentioned soy protein isolate is ≥95%.

[0014] Unless otherwise specified, all percentages in this application are percentages by mass.

[0015] To further improve mechanical properties, preferably, the raw materials of the heat-alkalized soybean protein adhesive include: 40 parts of heat-alkalized soybean protein adhesive, 1.8-2.2 parts of cyclic carbonated rosin derivative, 0.8-1.2 parts of microcrystalline cellulose, and 0.45-0.55 parts of calcium chloride; the parts are by weight.

[0016] The synthetic route for the above-mentioned epoxidized rosin derivatives is as follows:

[0017]

[0018]

[0019] As one preferred embodiment, the preparation of the above-mentioned cyclocarbonated rosin derivative includes the following steps:

[0020] 1) Fumaric acid, epichlorohydrin, and benzyltriethylammonium chloride are reacted at 100-120℃ for 1-2 hours under nitrogen atmosphere; wherein the mass ratio of fumaric acid to epichlorohydrin is 1:(2.8-3.2), and the benzyltriethylammonium chloride is 0.5-0.8% of the total mass of fumaric acid and epichlorohydrin;

[0021] 2) Add calcium oxide and sodium hydroxide to the reaction mixture obtained in step 1) and react at 50-60°C for 2-3 hours. After filtration and vacuum distillation, fumarate triglycidyl ether is obtained.

[0022] 3) Add tetrabutylammonium iodide and L-ascorbic acid to the fumarate triglycidyl ether obtained in step 2), and react it with CO2 at 60~80℃ to obtain rosin derivative; wherein the mass ratio of fumarate triglycidyl ether, tetrabutylammonium iodide and L-ascorbic acid is 10:(0.15~0.25):(0.05~0.15).

[0023] In steps 1-2 above, the mass ratio of fumaric acid, calcium oxide, and sodium hydroxide is 10:(2.5~3.5):(1.8~2.2).

[0024] In step 3) above, the CO2 pressure is maintained at 0.8~1.2 MPa during the reaction process.

[0025] The preparation method of the above-mentioned rosin derivative modified soybean protein adhesive includes the following steps:

[0026] 1) Dissolve the cyclic carbonated rosin derivative in ethanol, then add it to the heat-alkalized soybean protein adhesive and stir until homogeneous;

[0027] 2) Add microcrystalline cellulose to the adhesive obtained in step 1) and stir until homogeneous;

[0028] 3) Add calcium chloride to the adhesive obtained in step 2) and stir until uniform to obtain rosin derivative modified soybean protein adhesive.

[0029] In step 1) above, the mass ratio of ethanol to cyclic carbonated rosin derivative is 3:1.5-2.0.

[0030] Any techniques not mentioned in this invention are based on existing technologies.

[0031] Compared with the prior art, the present invention has achieved the following significant progress:

[0032] 1. This invention employs a thermal alkalization method to pretreat soybean protein. In the alkaline environment of sodium hydroxide solution, the negative charges within and between protein molecules repel each other, disrupting the ionic and hydrogen bonds in the tertiary and quaternary structures of the protein. Electrostatic repulsion causes the tightly folded, globular soybean protein to unfold, resulting in a random linear coil conformation. Simultaneously, under the influence of urea, the hydrogen bond network maintaining the secondary structure (α-helix and β-sheet) of the protein is further disrupted. Synergistically with sodium hydroxide, this further loosens the structure of the soybean protein molecules, exacerbating the exposure of internal hydrophobic regions and functional groups (such as -OH, -COOH, and -NH2).

[0033] 2. The "protein-cellulose" intercalation system constructed in this invention greatly improves the adhesive properties of soybean protein. The dual-network structure formed by cellulose and soybean protein molecules enhances the adhesive's resistance to debonding under stress, and the fiber intercalation avoids stress concentration. This structural engineering design overcomes the brittleness problem of thermally alkalized soybean protein molecules, effectively improving the mechanical properties of the adhesive.

[0034] 3. This invention effectively improves the curing efficiency of soybean protein adhesives through the synergistic effect of thermal alkalization pretreatment and metal ion treatment. Thermal alkalization transforms easily aggregated protein particles into a more water-soluble, homogeneous fluid. This allows less water to be added to the adhesive to maintain its high fluidity, while simultaneously reducing curing time. 2+ It binds to proteins through coordination bonds to form stable "calcium bridges." This coordination crosslinking is faster than physical crosslinking formed by water evaporation, hydrogen bonding, or hydrophobic interactions, thus accelerating the curing of the adhesive. Attached Figure Description

[0035] Figure 1 These are adhesive strength diagrams for various examples of the present invention;

[0036] Figure 2 These are adhesive strength diagrams for various embodiments of the present invention under different hot-pressing times;

[0037] Figure 3 Fourier transform infrared spectra of rosin derivatives; Detailed Implementation

[0038] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0039] In the examples, unless otherwise specified, the process is carried out at room temperature (15~25℃); unless otherwise specified, the stirring speed is 200r / min; unless otherwise specified, the stirring time is 5 minutes.

[0040] Example 1

[0041] 1) Preparation of rosin derivative: 50g fumaric acid, 150g epichlorohydrin, and 1.52g benzyltriethylammonium chloride were added to a round-bottom flask and heated to 117℃ under a nitrogen atmosphere with stirring for 2h. After the reaction was complete, the temperature was lowered to 60℃, and 10.68g sodium hydroxide and 14.98g calcium oxide were added to the round-bottom flask. The reaction was continued at 60℃ with stirring for 3h. The reaction product was filtered through diatomaceous earth, and the filtrate was vacuum distilled at 100℃. The remaining liquid was the epoxidized rosin derivative. 50g of the epoxidized rosin derivative, 1g tetrabutylammonium iodide, and 0.5g L-ascorbic acid were mixed evenly and placed in a reaction vessel. CO2 was introduced, and the reaction was continuously stirred at 80℃ and 1MPa for 24h (maintaining a CO2 pressure of 1MPa during the reaction) to obtain the cyclic carbonated rosin derivative.

[0042] 2) Pretreatment of soybean protein adhesive: Add 8g sodium hydroxide and 20g urea to 30g deionized water. After they are completely dissolved, add 10g soybean protein isolate (purchased from Shanghai Maclean Biochemical Technology Co., Ltd., containing 95% protein, 3% carbohydrates, 1.5% oil and 0.5% ash). Stir until uniform and heat to 60℃. Continue the reaction for 30 minutes to obtain thermally alkalized soybean protein adhesive.

[0043] 3) Preparation of rosin derivative modified soybean protein adhesive: Dissolve 1g of cyclic carbonated rosin derivative in 3g of ethanol, then add 40g of thermally alkalized soybean protein adhesive, stir the two evenly, add 0.5g of microcrystalline cellulose (Shanghai Maclean Biochemical Technology Co., Ltd., 9004-34-6, < 25µm) and stir evenly, then add 0.3g of calcium chloride and stir until the system is uniform.

[0044] Example 2

[0045] The material quantities used in the preparation of rosin derivative modified soybean protein adhesive are as follows: 3g ethanol, 1.5g cyclocarbonated rosin derivative, 40g thermally alkalized soybean protein adhesive, 0.75g microcrystalline cellulose, 0.4g calcium chloride, and the rest are the same as in Example 1.

[0046] Example 3

[0047] The material quantities used in the preparation of rosin derivative modified soybean protein adhesive are as follows: 3g ethanol, 2g cyclic carbonated rosin derivative, 40g thermally alkalized soybean protein adhesive, 1g microcrystalline cellulose, 0.5g calcium chloride, and the rest are the same as in Example 1.

[0048] Example 4

[0049] The material quantities used in the preparation of rosin derivative modified soybean protein adhesive are as follows: 3g ethanol, 2.5g cyclocarbonated rosin derivative, 40g thermally alkalized soybean protein adhesive, 1.25g microcrystalline cellulose, 0.6g calcium chloride, and the rest are the same as in Example 1.

[0050] Example 5

[0051] The material quantities used in the preparation of rosin derivative modified soybean protein adhesive are as follows: 3g ethanol, 3g cyclocarbonated rosin derivative, 40g thermally alkalized soybean protein adhesive, 1.5g microcrystalline cellulose, 0.7g calcium chloride, and the rest are the same as in Example 1.

[0052] Comparative Example 1

[0053] Mix 10g of soy protein isolate with 30g of water until smooth.

[0054] Comparative Example 2

[0055] Weigh 40g of the heat-alkalized soybean protein adhesive prepared in Example 1.

[0056] Comparative Example 3

[0057] Weigh 40g of the thermally alkalized soybean protein adhesive prepared in Example 1, add 1g of cellulose and stir until the system is homogeneous.

[0058] Comparative Example 4

[0059] Weigh 40g of the thermally alkalized soybean protein adhesive prepared in Example 1, add 1g of calcium chloride and stir until the system is homogeneous.

[0060] Comparative Example 5

[0061] Dissolve 2g of cyclic carbonated rosin derivative in 3g of ethanol, add 40g of thermally alkalized soybean protein adhesive prepared in Example 1, and stir until the system is homogeneous.

[0062] Comparative Example 6

[0063] 1g of microcrystalline cellulose and 1g of calcium chloride were mixed with 40g of the thermally alkalized soybean protein adhesive prepared in Example 1 and stirred until the system was homogeneous.

[0064] Comparative Example 7

[0065] Dissolve 2g of cyclic carbonated rosin derivative in 3g of ethanol, add 1g of microcrystalline cellulose, and mix with 40g of thermally alkalized soybean protein adhesive prepared in Example 1. Stir until the system is homogeneous.

[0066] Comparative Example 8

[0067] Dissolve 2g of cyclic carbonated rosin derivative in 3g of ethanol, add 1g of calcium chloride, and mix with 40g of thermally alkalized soybean protein adhesive prepared in Example 1. Stir until the system is homogeneous.

[0068] Comparative Example 9

[0069] The difference from Example 3 is that the cyclic carbonated rosin derivative is replaced with an epoxidized rosin derivative. All other aspects are the same as in Example 3.

[0070] Comparative Example 10

[0071] The difference from Example 3 is that the cyclic carbonated rosin derivative is replaced with pentaerythritol rosin. All other aspects are the same as in Example 3.

[0072] Comparative Example 11

[0073] The difference from Example 3 is that the cyclic carbonated rosin derivative is replaced with rosin glycerol ester. All other aspects are the same as in Example 3.

[0074] Comparative Example 12

[0075] Unlike Example 3, sodium hydroxide and urea are not added in step 2).

[0076] Comparative Example 13

[0077] Unlike Example 3, sodium hydroxide is not added in step 2).

[0078] Comparative Example 14

[0079] Unlike Example 3, urea is not added in step 2).

[0080] Test case

[0081] Three-layer plywood was prepared using the soybean protein adhesives prepared in Examples 1-5 and Comparative Examples 1-14 of this invention, respectively. The poplar veneer dimensions were 300mm × 300mm × 3mm. The plywood was prepared according to the following hot-pressing process:

[0082] The poplar veneer was dried in an oven at 60°C until the moisture content was 12%, and the glue application rate was 200g / m². 2Under the specified conditions, after applying adhesive to one side, two poplar veneers with the adhesive applied were stacked in a crisscross pattern. The unadhesive-free veneer was placed on top of the two adhesive-coated veneers to form the plywood. After assembly, the plywood was pre-pressed at 1.5 MPa for 10 minutes in a hot press at room temperature. The pre-pressed plywood was then placed in the hot press, with the pressure set at 2.0 MPa, the temperature at 130℃, and the pressing time at 4 minutes. After hot pressing, plywood made with rosin derivative-modified soybean protein adhesive was obtained. Results for each example are shown in Tables 1-2.

[0083] Example 3 was also applied to the above hot-pressing process, but the hot-pressing time was changed. After hot pressing, plywood made of rosin derivative modified soybean protein adhesive was obtained. The results are shown in Table 3.

[0084] The product's performance was tested according to the testing methods in GB / T17657-2013 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels".

[0085] The obtained plywood was prepared into specimens according to the relevant standards for the determination of adhesive layer shear strength in GB / T 17657-2013. The specimen size was 25×100mm, the groove depth was 1 / 2 of the specimen thickness, the kerf width was 3mm, and the shear length was 25mm. The specimens were then placed in a universal testing machine to determine the dry shear strength of the soybean protein adhesive. Five measurements were taken for each group, and the average value was recorded.

[0086] The cut specimens were immersed in hot water at (63±3)℃ for 3 hours, then cooled at room temperature for 10 minutes, dried, and placed in a universal testing machine to determine the wet shear strength of the soybean protein adhesive. Each group was measured 5 times and the average value was taken.

[0087]

[0088]

[0089]

[0090] Depend on Figure 1It can be seen that the original soybean protein adhesive prepared in Comparative Example 1 has a low dry shear strength, and the heat-alkalized soybean protein adhesive prepared in Comparative Example 2 cannot achieve bonding due to its low cohesion. The dry shear strengths of the adhesives in Examples 1-4 are all greater than 0.7 MPa, far exceeding the strength requirements of Class I plywood in GB / T17657-2013. The dry shear strength of the soybean protein adhesives in Comparative Examples 3-11 is the highest, showing a certain improvement compared to Comparative Example 1. This indicates that the modifier can improve the degree of cross-linking in the system, but its improvement on the adhesive bonding performance is limited. The dry shear strength of Examples 1-3 gradually increases, indicating that a dense cross-linked network structure is formed between the cross-linking agent and soybean protein molecules, effectively improving the adhesive bonding performance. Comparative Example 5 shows a certain improvement in wet shear strength compared to Comparative Example 1, while Comparative Examples 3-4 do not show a significant improvement. This indicates that the improvement in the water resistance of the adhesive is mainly attributed to the addition of rosin derivatives.

[0091] Depend on Figure 2 It can be seen that the dry shear strength of the rosin derivative soybean protein adhesive prepared in Example 3 gradually increases with the increase of hot pressing time, and the bonding strength reaches 3.5816 MPa under the condition of hot pressing for 4 minutes. Further increasing the hot pressing time does not significantly increase the bonding strength, indicating that the rosin derivative modified soybean protein adhesive completes curing within 4 minutes of hot pressing. The improvement in the hot pressing process is mainly attributed to the hot alkalization treatment, which significantly increases the solid content of the adhesive, and the dense coordination network composed of soybean protein, cellulose, and calcium chloride greatly improves the curing efficiency of the adhesive.

[0092] like Figure 3 As shown, infrared spectroscopy reveals that epoxidized rosin derivatives exhibit a fluorescence intensity at 908 cm⁻¹. -1 and 845cm -1 The presence of a characteristic absorption peak for the epoxy group at 908 cm⁻¹ indicates successful carboxyl epoxidation. The infrared spectrum of the cyclocarbonate-modified rosin derivative shows a peak at 908 cm⁻¹. -1 and 845cm -1 The characteristic absorption peak value of the epoxy group at 1796 cm⁻¹ decreases, with the peak value decreasing at 1796 cm⁻¹. -1 The presence of characteristic absorption peaks for epoxy groups indicates that the number of epoxy groups decreased after the affinity addition reaction, and the cyclocarbonate rosin derivative was successfully constructed.

Claims

1. A rosin derivative modified soybean protein adhesive, characterized in that, Raw materials include: The composition comprises 40 parts of heat-alkalized soybean protein adhesive, 1.5-2.0 parts of cyclic carbonated rosin derivative, 0.5-1.0 parts of microcrystalline cellulose, and 0.3-0.5 parts of calcium chloride; the parts are by weight. The preparation method of the thermally alkalized soybean protein adhesive is as follows: urea and sodium hydroxide are dissolved in deionized water, soybean protein isolate is added to the solution, and the mixture is heated and stirred to react, thereby obtaining the thermally alkalized soybean protein adhesive. The structure of the cyclic carbonated rosin derivative is as follows: 。 2. The thermally alkalized soybean protein adhesive as described in claim 1, characterized in that, When preparing the heat-alkalized soybean protein adhesive, the mass ratio of soybean protein isolate, urea, sodium hydroxide and deionized water is 5:(9-11):(3.5-4.5):(14-16).

3. The thermally alkalized soybean protein adhesive as described in claim 2, characterized in that, Soy protein isolate purity ≥95%.

4. The heat-alkalized soybean protein adhesive as described in any one of claims 1-3, characterized in that, When preparing the thermally alkalized soybean protein adhesive, the reaction temperature is 50~60℃ and the time is 20~30min.

5. The heat-alkalized soybean protein adhesive as described in any one of claims 1-3, characterized in that, Raw materials include: The ingredients are: 40 parts of heat-alkalized soybean protein adhesive, 1.8-2.2 parts of cyclic carbonated rosin derivative, 0.8-1.2 parts of microcrystalline cellulose, and 0.45-0.55 parts of calcium chloride; the parts are by weight.

6. The heat-alkalized soybean protein adhesive as described in any one of claims 1-3, characterized in that, The preparation of cyclocarbonated rosin derivatives includes the following steps: 1) Fumaric acid, epichlorohydrin, and benzyltriethylammonium chloride are reacted at 100-120℃ for 1-2 hours under nitrogen atmosphere; wherein the mass ratio of fumaric acid to epichlorohydrin is 1:(2.8-3.2), and the benzyltriethylammonium chloride is 0.5-0.8% of the total mass of fumaric acid and epichlorohydrin; 2) Add calcium oxide and sodium hydroxide to the reaction material obtained in step 1) and react at 50-60°C for 2-3 hours. After filtration and vacuum distillation, fumarate triglycidyl ether is obtained. 3) Add tetrabutylammonium iodide and L-ascorbic acid to the fumarate triglycidyl ether obtained in step 2), and react it with CO2 at 60~80℃ to obtain cyclic carbonated rosin derivative; wherein the mass ratio of fumarate triglycidyl ether, tetrabutylammonium iodide and L-ascorbic acid is 10:(0.15~0.25):(0.05~0.15).

7. The heat-alkalized soybean protein adhesive as described in claim 6, characterized in that, In steps 1-2), the mass ratio of fumaric acid, calcium oxide, and sodium hydroxide is 10:(2.5~3.5):(1.8~2.2).

8. The rosin derivative modified chitosan adhesive as described in claim 6, characterized in that: In step 3), the CO2 pressure is maintained at 0.8~1.2 MPa during the reaction.

9. A method for preparing a rosin derivative modified soybean protein adhesive according to any one of claims 1-8, characterized in that, Includes the following steps: 1) Dissolve the cyclic carbonated rosin derivative in ethanol, then add it to the heat-alkalized soybean protein adhesive and stir until homogeneous; 2) Add microcrystalline cellulose to the adhesive obtained in step 1) and stir until homogeneous; 3) Add calcium chloride to the adhesive obtained in step 2) and stir until uniform to obtain rosin derivative modified soybean protein adhesive.

10. The preparation method according to claim 9, characterized in that, In step 1), the mass ratio of ethanol to cyclic carbonated rosin derivative is 3:1.5-2.0.

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