Plant protein adhesive, preparation method and application thereof

Abstract

The present application relates to the technical field of molecular materials, and particularly relates to a plant protein adhesive as well as a preparation method and application thereof. The plant protein adhesive comprises plant protein, protease, a catalyst, cysteine and calcium phosphate subjected to in-situ mineralization; the mass ratio of the plant protein, the cysteine and the calcium phosphate subjected to in-situ mineralization is (10-25):(2-10):(0.1-1). The present application forms an organic-inorganic hybrid adhesive grafted with cysteine through an amidation reaction and in-situ mineralization of calcium phosphate, the adhesive has strong cohesion, strong interface interaction with wood and high bonding strength. The adhesive provided by the present application has high water resistance, mildew resistance, antibacterial performance, flame retardance and artificial board recycling performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molecular materials, and particularly relates to a plant protein adhesive as well as a preparation method and application thereof. BACKGROUND

[0002] Artificial boards are widely used in the fields of indoor decoration, furniture, building, etc. At the same time, a large amount of waste artificial boards and products thereof are generated every year. At present, the existing technology mainly adopts landfill and incineration to process the waste artificial boards, and only a small part is recycled. However, the artificial boards and products thereof contain chemical raw materials such as urea-formaldehyde resin and phenol-formaldehyde resin, and the landfill treatment not only occupies land and increases transportation cost, but also pollutes the soil, water source and environment if improperly treated. The harmful gases generated by the incineration treatment also pollute the atmospheric environment. In addition, the aldehyde-based adhesive is also difficult to realize the recycling of artificial boards.

[0003] The plant protein adhesive becomes the most promising large-scale alternative to the aldehyde-based resin adhesive in the artificial board industry due to its advantages of rich raw materials, renewability and biodegradability. However, the plant protein adhesive usually has low mechanical properties, which limits its large-scale application. SUMMARY

[0004] In order to solve the problems in the prior art, the present application provides a plant protein adhesive as well as a preparation method and application thereof. An organic-inorganic hybrid system grafted with cysteine is formed through an amidation reaction and in-situ mineralized calcium phosphate, so that the bonding strength of the adhesive is significantly improved.

[0005] In a first aspect, the present application provides a plant protein adhesive, comprising: plant protein, protease, catalyst, cysteine and in-situ mineralized calcium phosphate.

[0006] The mass ratio of the plant protein, cysteine and in-situ mineralized calcium phosphate is (10-25):(2-10):(0.1-1).

[0007] The present application is inspired by the structure of keratin, and an organic-inorganic hybrid plant protein adhesive is prepared by using cysteine modification and in-situ mineralized calcium phosphate, so that the cohesion is significantly improved, the water-resistant bonding performance is also significantly improved, and a large number of thiol bonds are introduced to help the formation of disulfide bonds. Further, the plant protein adhesive comprises, by weight fraction:

[0008] plant protein 15-20 parts, cysteine 3-5 parts and in-situ mineralized calcium phosphate 0.3-0.7 parts.

[0009] Further, the plant protein adhesive comprises, by weight fraction:

[0010] Plant protein 15-20 parts, protease 0.1-0.3 parts, catalyst 0.5-1 parts, cysteine 3-5 parts and in-situ mineralized calcium phosphate 0.3-0.7 parts.

[0011] Further, the protease comprises one or more of alkaline protease, pepsin, papain or bromelain, preferably bromelain; and the catalyst comprises EDC and NHS.

[0012] Further, the mass ratio of EDC and NHS is (3-7):1.

[0013] EDC: (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride), and NHS: N-hydroxysuccinimide.

[0014] Further, the molecular modifier and sodium tetraborate are further included.

[0015] Further, the mass ratio of the molecular modifier and sodium tetraborate is (6-10):1.

[0016] The present application further introduces a molecular modifier and sodium tetraborate into the adhesive system, the molecular modifier and sodium tetraborate form a dynamic borate ester bond with the diol exposed by the ring-opening reaction of the enzymatic protein, and the dynamic disulfide bond cooperatively improves the application of the adhesive in the recycling of the artificial board.

[0017] Further, the in-situ mineralized calcium phosphate is prepared by the following method:

[0018] The calcium chloride solution and the dibasic potassium phosphate solution are mixed and then added into the system of the plant protein adhesive; the mass ratio of calcium chloride in the calcium chloride solution to dibasic potassium phosphate in the dibasic potassium phosphate solution is (2.5-3.5):(1.2-2.4).

[0019] Further, the plant protein comprises one or more of water-soluble soybean, peanut or cottonseed protein isolate.

[0020] As a preferred specific embodiment, the present application provides a plant protein adhesive, comprising:

[0021] Plant protein 15-20 parts, protease 0.1-0.3 parts, catalyst 0.5-1 parts, cysteine 3-5 parts, in-situ mineralized calcium phosphate 0.3-0.7 parts, molecular modifier 3-6 parts and sodium tetraborate 0.5-1 parts.

[0022] In the second aspect, the present application provides a preparation method of a plant protein adhesive, comprising:

[0023] The plant protein enzymolysis dispersion liquid is obtained by enzymolysis of plant protein by protease; the plant protein enzymolysis dispersion liquid, cysteine and a catalyst are mixed; a molecular modifier and sodium tetraborate are further mixed to obtain an adhesive mixture; a calcium chloride solution and a dimethyl hydrogen phosphate solution are added to the adhesive mixture.

[0024] Further, the enzymolysis comprises: enzymolysis for 10-15 minutes under the condition of 50-60 DEG C.

[0025] The plant protein enzymolysis dispersion liquid, cysteine and a catalyst are mixed and uniformly mixed for 5-8 hours.

[0026] The molecular modifier and sodium tetraborate are mixed and uniformly mixed for 20-30 minutes.

[0027] The calcium chloride solution and the dimethyl hydrogen phosphate solution are added to the adhesive mixture and uniformly mixed for 20-30 minutes.

[0028] The present application has the following effects:

[0029] The present application forms an organic-inorganic hybrid system grafted with cysteine through amidation reaction and in-situ mineralization of calcium phosphate, which significantly improves the cohesion of the adhesive. Meanwhile, the present application introduces a molecular modifier and sodium tetraborate, so that the adhesive can be applied to the recycling of artificial boards; and the bonding strength is further improved.

[0030] The plant protein adhesive prepared by the present application is green and environmentally friendly, has no harmful substance release, has good water resistance, strong interface interaction with wood, mildew resistance, antibacterial property and flame retardant property, and can effectively promote the practical application of the plant protein adhesive and the recycling of artificial boards. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0032] Embodiment 1

[0033] The present embodiment provides a preparation method of a multifunctional plant protein adhesive, which specifically uses the following raw materials in the following weight ratio:

[0034]

[0035]

[0036] The dispersing medium is deionized water, the molecular modifier is propylene glycol, and the plant protein is soybean protein isolate.

[0037] The specific processing procedure is as follows:

[0038] (1) According to the weight ratio, each component is weighed, the plant protein and bromelain are dispersed in deionized water, and stirred at 55°C for 10 min, and then the mixture is transferred to a water bath at 100°C for 5 min to inactivate the bromelain.

[0039] (2) L-cysteine and catalyst (EDC and NHS) are uniformly dispersed in the plant protein enzymatic dispersion solution obtained in step (1), and stirred for 6 h.

[0040] (3) The molecular modifier and sodium tetraborate are uniformly dispersed in the dispersion solution obtained in step (2), and stirred at room temperature for 20 min.

[0041] (4) The calcium chloride solution and potassium phosphate dibasic solution are added to the adhesive mixture in step (3), and stirred at room temperature for 20 min to obtain a calcium phosphate deposited adhesive.

[0042] Example 2

[0043] The present embodiment provides a preparation method of a multifunctional plant protein adhesive, and the specific raw materials are as follows:

[0044]

[0045] The dispersing medium is deionized water, the molecular modifier is propylene glycol, and the plant protein is soybean protein isolate.

[0046] The specific processing procedure is the same as that of Example 1.

[0047] Test Example 1

[0048] In this test example, the adhesives prepared by Examples 1-2 and a plurality of control groups are further used to prepare three-layer plywood, and the bonding strength test is performed.

[0049] Control group 1: plant protein 15 g and deionized water 70 g are used. Correspondingly, the plant protein is directly dispersed in deionized water.

[0050] Control group 2: plant protein 15 g, bromelain 0.1 g and deionized water 70 g are used. Correspondingly, only the enzymatic process of step (1) in the example is performed.

[0051] Control group 3: plant protein 15g, bromelain 0.1g, catalyst (EDC:NHS = 0.5:0.1g), L-cysteine 3g and deionized water 66.3g. Correspondingly, only the enzymatic hydrolysis of step (1) and the mixing of cysteine of step (2) in the example are carried out.

[0052] Control group 4: plant protein 15g, bromelain 0.1g, catalyst (EDC:NHS = 0.5:0.1g), L-cysteine 3g, molecular modifier 5g, deionized water 61.3g. Correspondingly, only the enzymatic hydrolysis of step (1) and the mixing of cysteine of step (2) in the example are carried out, and step (3), but only the molecular modifier is dispersed in the mixture.

[0053] Control group 5: melamine modified urea-formaldehyde resin (E0 grade) with a molar ratio of 1.01 to F / U was purchased from Shandong Qiansen Wood Co., Ltd.

[0054] Control group 6: plant protein 15g, bromelain 0.1g, catalyst (EDC:NHS = 0.5:0.1g), L-cysteine 3g, calcium chloride 0.3g, potassium hydrogen phosphate 0.2g and deionized water 65.8g. Correspondingly, only steps (1), (2) and (4) in the example are carried out.

[0055] Control group 7: plant protein 15g, bromelain 0.1g, molecular modifier 5g, sodium tetraborate 0.6g and deionized water 64.3g. Correspondingly, only the enzymatic hydrolysis step of step (1) and the processing flow of step (3) in the example are carried out.

[0056] The test method is as follows:

[0057] 1. Strength test

[0058] Poplar single board: moisture content dried to 12%; size 40cm*40cm*0.15cm.

[0059] According to the following normal preparation process:

[0060] Gluing: the amount of glue is 180g / m 2 .

[0061] Pressure, temperature, time: 1MPa, 120℃, 6min.

[0062] The performance of the cross-laminated product is detected according to the detection method of GB / T 17657-1999 "Experimental methods for physical and chemical properties of wood-based panels and veneered wood-based panels".

[0063] 2. The mold test is as follows:

[0064] 15 g of the synthetic adhesive was transferred to a petri dish and then stored in a constant temperature and humidity chamber with a relative humidity of 50% and a temperature of 30°C.

[0065] 3. The antibacterial activity of the adhesives of Example 1-2 and Comparative Example 1-7 was tested against S. aureus and E. coli, respectively.

[0066] 4. Artificial board recycling test:

[0067] The plywood prepared using the adhesives of Example 1-2 and Comparative Example 1-7 was crushed into chips. Then, the adhesives of Comparative Example 1-7 and Example 1-2 were re-applied, respectively, and the particle board was prepared according to the following normal preparation process:

[0068] Gluing: the amount of glue applied was 14%.

[0069] Pressure, temperature, time: 3 MPa, 180°C, 6 min.

[0070] The MOR, MOE, and IB of the particle board product were detected according to the detection method of GB / T 17657-2013 "Test methods of physical and mechanical properties of wood-based panels and wood-based panel veneers".

[0071] 5. Test results

[0072] The test results are shown in the following table:

[0073] Table 1 Comprehensive performance of plant protein adhesive

[0074]

[0075]

[0076] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limiting; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for part of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solution to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A plant protein adhesive, characterized in that, The plant protein adhesive comprises, by weight, the following: The ingredients include 15-20 parts plant protein, 0.1-0.3 parts protease, 0.5-1 part catalyst, 3-5 parts cysteine, and 0.3-0.7 parts calcium phosphate that has been mineralized in situ.

2. The plant protein adhesive according to claim 1, characterized in that, The protease includes one or more of alkaline protease, pepsin, papain, or bromelain; and / or the catalyst includes EDC and NHS.

3. The plant protein adhesive according to claim 2, characterized in that, The protease is bromelain.

4. The plant protein adhesive according to any one of claims 1-3, characterized in that, Also includes: Molecular modifiers and sodium tetraborate.

5. The plant protein adhesive according to claim 1, characterized in that, The in-situ mineralized calcium phosphate was prepared by the following method: The mixture of calcium chloride solution and dipotassium hydrogen phosphate solution is added to the system of the plant protein adhesive; the mass ratio of calcium chloride in the calcium chloride solution to dipotassium hydrogen phosphate in the dipotassium hydrogen phosphate solution is (2.5-3.5):(1.2-2.4).

6. The plant protein adhesive according to claim 1, characterized in that, By weight, it includes: The ingredients include 15-20 parts plant protein, 0.1-0.3 parts protease, 0.5-1 part catalyst, 3-5 parts cysteine, 0.3-0.7 parts in-situ mineralized calcium phosphate, 3-6 parts molecular modifier, and 0.5-1 parts sodium tetraborate.

7. The plant protein adhesive according to any one of claims 1-3, 5, or 6, characterized in that, The plant protein includes one or more of the following: water-soluble soybean, peanut, or cottonseed protein isolate.

8. The plant protein adhesive according to claim 4, characterized in that, The plant protein includes one or more of the following: water-soluble soybean, peanut, or cottonseed protein isolate.

9. A method for preparing the plant protein adhesive according to any one of claims 1-8, characterized in that, include: Plant protein was hydrolyzed with proteases to obtain a plant protease hydrolysate dispersion; the plant protease hydrolysate dispersion, cysteine, and catalyst were mixed; a molecular modifier and sodium tetraborate were further mixed to obtain an adhesive mixture; calcium chloride solution and dimethyl hydrogen phosphate solution were added to the adhesive mixture.

10. The preparation method according to claim 9, characterized in that, The enzymatic hydrolysis includes: enzymatic hydrolysis at 50–60°C for 10–15 minutes; and / or The plant protease hydrolysis dispersion, cysteine, and catalyst are mixed and stirred for 5–8 hours; and / or The mixed molecular modifier and sodium tetraborate were then mixed for 20–30 minutes; and / or, After adding the calcium chloride solution and dimethyl hydrogen phosphate solution to the adhesive mixture, mix well for 20-30 minutes.

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