Disclosure of Invention
The invention discovers that the protein adhesive prepared from wood fibers is similar to a reinforced concrete structure, and the strength and the toughness of the adhesive can be improved to a certain extent. However, the wood fiber has poor dispersibility in aqueous solution, and the bonding between the wood fiber and the protein molecule is mainly hydrogen bonds, so that the interfacial bonding capability is weak, and the use requirement cannot be met well. Further, the invention surprisingly discovers that the strength and toughness of the adhesive can be remarkably improved by further preparing the modified wood fiber into the protein adhesive.
Specifically, the invention provides a modified wood fiber reinforced plant protein adhesive, which comprises the raw materials of protein meal, modified wood fibers, a cross-linking agent and water.
In some embodiments of the present invention, the modified wood fiber reinforced plant protein adhesive is prepared from raw materials including protein meal, modified wood fiber, a cross-linking agent and water.
In some embodiments of the present invention, the weight ratio of the raw material protein meal, the modified wood fibers, the cross-linking agent and the water of the modified wood fiber reinforced plant protein adhesive is (12-20): (0.05-0.2): (2-4): (25-45).
In some embodiments of the present invention, the weight ratio of the raw material protein meal, the modified wood fibers, the cross-linking agent and the water of the modified wood fiber reinforced plant protein adhesive is (15-18): (0.1-0.15): (3-3.6): (30-35).
In some embodiments of the present invention, the weight ratio of the sum of the weight of the raw protein meal, the modified wood fibers and the crosslinking agent of the modified wood fiber reinforced plant protein adhesive to the weight of water is (15-24): 30.
In some embodiments of the present invention, the weight ratio of the sum of the weight of the raw protein meal, the modified wood fibers and the crosslinking agent of the modified wood fiber reinforced plant protein adhesive to the weight of water is (18-23): 30.
In some embodiments of the present invention, the weight ratio of the raw protein meal, the modified wood fibers, the crosslinking agent and the water of the modified wood fiber reinforced plant protein adhesive is 18:0.2:4: 30.
Researches show that the raw materials in the proportion range can remarkably improve the strength and toughness of the adhesive.
In some embodiments of the invention, the protein meal is vegetable protein meal.
In some embodiments of the present invention, the protein meal is one or more of soybean meal, maple meal, peanut meal, castor meal, cottonseed meal, rapeseed meal, and distillers' grains.
In some embodiments of the invention, the protein meal has a particle size of 70-500 mesh.
In some embodiments of the invention, the protein meal has a particle size of 100-400 mesh.
In some embodiments of the invention, the protein meal has a particle size of 200-250 mesh.
The protein meal in the particle size range is powdery, and the powder is easy to disperse and is beneficial to full contact and reaction with the cross-linking agent.
In some embodiments of the invention, the protein meal is defatted protein meal.
In some embodiments of the invention, the protein content of the protein meal is greater than 40% (w/w).
In some embodiments of the invention, the protein content of the protein meal is 40-60% (w/w).
In some embodiments of the invention, the protein content of the protein meal is 43% (w/w).
In some embodiments of the present invention, the crosslinking agent is selected from one or more of polyamide polyamine epichlorohydrin resin (PAE), epoxy crosslinking agent glycerol triglycidyl ether (PTGE), ethylene glycol diglycidyl ether (EDGE), and the like, and is preferably PAE or PTGE.
In some embodiments of the present invention, the modified wood fiber of the present invention comprises one or both of carboxymethylated wood fiber, isocyanate modified wood fiber.
In some embodiments of the present invention, the carboxymethylated wood fiber is prepared by treating dried wood fiber with an aqueous solution of sodium monochloroacetate; then adding sodium hydroxide solution for full reaction; washing until the pH is neutral or washing until no alkali exists; drying to obtain the product.
Wherein the concentration of the sodium hydroxide solution can be 35-40% (w/w); for example, in some embodiments at a concentration of 38.5% (w/w).
Further, the weight ratio of the wood fiber to the sodium monochloroacetate is (15-25): 25-35), and more preferably 20: 30.
Further, the weight ratio of the wood fiber to the sodium hydroxide is (15-25): (60-70), more preferably 20: 65.
In some embodiments of the present invention, the method for preparing carboxymethylated wood fibers comprises:
1) taking dried wood fiber and sodium monochloro acetate, adding water, and fully reacting;
2) adding sodium hydroxide into the reaction system in the step 1), and fully reacting at room temperature;
3) washing the reaction products obtained in the step 2) to neutral pH or alkali-free sequentially; and (5) drying to obtain the finished product.
In the above-mentioned method for preparing carboxymethylated wood fibers,
the water is preferably distilled water;
in step 1), the reaction time is usually 3-5h, preferably 4 h; the reaction temperature is preferably 50 to 70 ℃ and preferably 60 ℃. Step 1) is preferably carried out under heating conditions in a water bath.
Sodium hydroxide solution can be added in the step 2), for example, the mass concentration of the sodium hydroxide solution is 35-40% (w/w); in some embodiments the concentration is 38.5% (w/w); the reaction time is preferably 22 to 26 hours, more preferably 24 hours.
The invention also comprises the carboxymethylated wood fiber prepared by the method.
In the invention, the isocyanate modified wood fiber is prepared by coating isocyanate on the surface of dry wood fiber serving as a raw material. Preferably, the surface is coated with isocyanate in a weight ratio of 20-60%, more preferably 50% to the wood fibre raw material. Specifically, the isocyanate can be prepared into an isocyanate solution by using acetone as a solvent, and then the isocyanate solution is sprayed on the surface of the wood fiber.
Wherein, the isocyanate is preferably 4,4' -diphenylmethane-diisocyanate (MDI), and one or more of isophorone diisocyanate (IPDI), dicyclohexyl methane diisocyanate (HMDI), Hexamethylene Diisocyanate (HDI), Toluene Diisocyanate (TDI), etc. can also be used.
In some embodiments of the present invention, the isocyanate-modified wood fiber is prepared by a method comprising: placing the dried wood fiber in a closed container, spraying isocyanate solution (acetone as solvent) in a tumbling condition until the isocyanate solution is completely covered on the fiber surface as much as possible.
The invention also comprises the isocyanate modified wood fiber prepared by the method.
Unless otherwise specified, the drying in the present invention generally means drying to an absolutely dry state. Drying can be carried out by methods customary in the art, for example by drying in an electric forced air drying cabinet at 103. + -. 2 ℃ to the absolute dry state.
The wood fiber raw material used in the present invention may be selected conventionally in the art, and for example, raw materials such as poplar fiber and eucalyptus fiber may be selected.
The modified wood fiber reinforced plant protein adhesive can be prepared by adopting a conventional method in the field.
Specifically, the invention also provides a preparation method of the modified wood fiber reinforced plant protein adhesive, which comprises the following steps: adding the modified wood fiber into water, and stirring to uniformly disperse the modified wood fiber; adding soybean meal powder and a cross-linking agent, and uniformly stirring to obtain the product.
The invention also comprises the application of the modified wood fiber reinforced plant protein adhesive in the fields of wood, bamboo, furniture, printed matters, decoration, buildings and the like.
In particular, the present invention also includes wood processed products, bamboo processed products printed products, ornaments, buildings and the like, such as artificial boards such as plywood, shaving board, medium density fiberboard and laminated wood board and the like, which contain the modified wood fiber reinforced plant protein adhesive.
The electrostatic repulsion between the modified wood fibers prepared by the embodiment of the invention is beneficial to uniform distribution of the fibers in the protein matrix, is not easy to agglomerate, and provides a high-quality material for the modified protein adhesive.
The wood fiber is an organic flocculent fiber substance obtained by mechanical processing of wood, and has the advantages of low cost (500- & ltyuan/ton), high fiber strength, large-scale production and the like.
The modified wood fiber prepared by the embodiment of the invention is used as a reinforcing toughening body and interpenetrates and permeates with the protein matrix to form a stable and compact cross-linked network structure of reinforcing steel bar (modified wood fiber) concrete (epoxy cross-linking agent) cement (protein matrix), effectively prevents water intrusion and improves the water resistance of the protein adhesive. In addition, the solid content and the thermal stability of the modified bean gum are improved.
After the surface chemical treatment (carboxymethyl modification and isocyanate modification treatment) is carried out on the wood fiber, the surface activity of the wood fiber is enhanced, and the surface active group of the fiber can be better crosslinked with protein and a crosslinking agent, so that the prepared protein adhesive has a compact structure, and compared with an unmodified adhesive, the strength of the prepared protein adhesive can be increased by 158-171%. Meanwhile, the long-chain flocculent structure of the wood fiber improves the toughness of the adhesive. Can meet the requirement of industrial production.
The modified adhesive prepared by the embodiment of the invention has no formaldehyde release, and the manufactured artificial board has no formaldehyde release, thereby thoroughly solving the problem of formaldehyde pollution of the artificial board. The preparation method of the adhesive is simple, low in cost, good in water resistance and high in toughness of a cured adhesive layer.
The modified adhesive prepared by the embodiment of the invention obviously improves the bonding strength and toughness, is convenient to construct and has proper price.
Detailed Description
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention. The examples do not show the specific techniques or conditions, according to the technical or conditions described in the literature in the field, or according to the product specifications.
The wood fiber used below is poplar wood fiber.
The used soybean meal contains more than or equal to 40% (w/w) of protein, and the granularity is more than or equal to 150 meshes.
The epoxy crosslinker used below is glycerol triglycidyl ether (PTGE).
The carboxymethylated wood fibres used below were prepared by the following method:
the preparation of carboxymethylated wood fibre material comprises distilled water, sodium monochloroacetate, wood fibre and sodium hydroxide. The weight parts of the components are as follows:
the preparation method comprises the following steps:
1) and (3) placing the wood fiber in an electric heating air blowing drying oven for 24 hours at the temperature of 103 +/-2 ℃ until the wood fiber is dried.
2) Sequentially weighing sodium monochloro acetate, distilled water and dried wood fiber in a beaker according to the mixture ratio,
heating in water bath at 60 deg.C and stirring for 4 hr.
3) Adding sodium hydroxide (in the form of sodium hydroxide solution with the mass fraction of 38.5%) according to the above proportion, and stirring the mixture for 24h at room temperature; washing to neutral or alkali-free.
4) And (3) placing the cleaned fiber in an oven at 103 +/-2 ℃ for 24 hours to obtain the dried carboxymethylated wood fiber.
The isocyanate-modified wood fibers used below were prepared by the following method:
the isocyanate modified wood fiber material is prepared by wood fiber, isocyanate and acetone. The preparation method comprises the following steps:
1) taking a proper amount of wood fiber, placing the wood fiber in an electric heating forced air drying oven, and drying the wood fiber to be absolutely dry, wherein the temperature of the drying oven is set to be 103 +/-2 ℃.
2) Isocyanate was dissolved in a certain amount of acetone to prepare a solution having an isocyanate concentration of 10%.
3) And (3) placing the dried wood fiber into a closed container, spraying an isocyanate solution in a rolling process until the isocyanate solution is completely covered on the fiber surface as much as possible, wherein the weight ratio of isocyanate to the raw material fiber is 50%, and thus obtaining the isocyanate modified wood fiber.
Example 1 modified Wood fiber reinforced vegetable protein Adhesives and preparation thereof
1. Preparing materials (kg) according to the following weight ratio:
2. at room temperature, the carboxymethylated wood fiber is added into distilled water according to the proportion and stirred for 10min to be uniformly dispersed.
3. And (3) adding the soybean meal powder and the epoxy cross-linking agent into the mixture prepared in the step (2) according to the proportion, stirring for 30min, and uniformly mixing to prepare the modified wood fiber reinforced plant protein adhesive.
Example 2 modified Wood fiber reinforced vegetable protein Adhesives and preparation thereof
1. Preparing materials (kg) according to the following weight ratio:
2. at room temperature, the carboxymethylated wood fiber is added into distilled water according to the proportion and stirred for 10min to be uniformly dispersed.
3. And (3) adding the soybean meal powder and the epoxy cross-linking agent into the mixture prepared in the step (2) according to the proportion, stirring for 30min, and uniformly mixing to prepare the modified wood fiber reinforced plant protein adhesive.
Example 3 modified Wood fiber reinforced vegetable protein Adhesives and preparation thereof
1. Preparing materials (kg) according to the following weight ratio:
2. under the condition of normal temperature, 0.2kg of isocyanate modified wood fiber is added into 30kg of distilled water and stirred for 10min, so that the fiber is uniformly dispersed in the water solution.
3. And (3) sequentially adding 18kg of soybean meal powder and 4kg of epoxy cross-linking agent into the mixed solution prepared in the step (2), and uniformly stirring to prepare the modified wood fiber reinforced plant protein adhesive.
Example 4 modified Wood fiber reinforced vegetable protein Adhesives and preparation thereof
1. Preparing materials (kg) according to the following weight ratio:
2. under the condition of normal temperature, 0.1kg of isocyanate modified wood fiber is added into 30kg of distilled water and stirred for 10min, so that the fiber is uniformly dispersed in the water solution.
3. And (3) sequentially adding 12kg of soybean meal powder and 3.2kg of epoxy cross-linking agent into the mixed solution prepared in the step (2), and uniformly stirring to prepare the modified wood fiber reinforced plant protein adhesive.
Comparative example 1 protein adhesive and preparation thereof
1. Preparing materials (kg) according to the following weight ratio:
water 30
Soybean meal powder 18
Epoxy crosslinking agent 4.0
2. Under the condition of normal temperature, adding the soybean meal powder and the epoxy cross-linking agent into water according to the proportion, and uniformly stirring to prepare the protein adhesive.
Comparative example 2 pure wood fibrin adhesive and preparation thereof
1. Preparing materials (kg) according to the following weight ratio:
2. at normal temperature, 0.1kg of wood fiber (unmodified) is added into 30kg of distilled water, and stirred for 10min to uniformly disperse the fiber in the water solution.
3. And (3) adding 15kg of soybean meal powder and 3.6kg of epoxy cross-linking agent into the mixed solution prepared in the step (2) in sequence, and uniformly stirring to prepare the pure wood fiber protein adhesive.
Experimental example 1
The following experiments were conducted on the adhesives prepared in examples 1 to 4 and comparative examples 1 to 2, respectively. The specific experimental method is as follows:
the solid content test method comprises the following steps:
taking a proper amount of prepared adhesive m1g, placing the adhesive in a tin foil paper box, and recording the total weight m of the adhesive and the tin foil paper box2g, then placing the adhesive in an oven at the temperature of 122 +/-2 ℃ to be dried to constant weight, and recording the total weight m of the cured adhesive and the tin foil carton3g, the calculation formula of the solid content of the adhesive is as follows. The above tests were run in parallel 3 times and the average was taken.
Adhesive solid content (W)1) The calculation formula is as follows:
W1(%)=[m3-(m2-m1)]/m1×100%
pH value test method:
1) 50mL of adhesive is measured and poured into a beaker, and the beaker with the adhesive is placed into a constant temperature water bath (the temperature is 25 +/-1 ℃) as a sample for measuring the pH value.
2) After the temperature of the sample reaches stable equilibrium, the glass electrode of the acidimeter is washed clean by distilled water and wiped dry, and then the electrode is washed by test solution and inserted into the test sample for measurement.
3) And (4) continuously measuring for three times, and if the difference of the three pH values is more than 0.2, re-taking the three samples and measuring again until the difference of the pH values is not more than 0.2.
The adhesive performance test method comprises the following steps:
the test material is poplar veneer (200mm multiplied by 1.5 mm).
1) Coating an adhesive on one side of two single plates, wherein the application amount is 180 g/square meter, assembling three single plates in a direction vertical to the texture, and then carrying out hot pressing, wherein the hot pressing temperature is 122 ℃, the hot pressing time is 6min, and the hot pressing pressure is 1.05 MPa.
2) The prepared plywood is dried and ventilated for 24h according to the national standard GB/T9846-. And (3) placing the sample in water at 63 +/-2 ℃ for 3h, and testing the maximum load force (N) of the glue line fracture of the plywood by using a universal mechanical testing machine, wherein the testing speed is 10 mm/min. The strength data for 6 samples were obtained for each veneer and averaged.
Wet shear strength (W) of plywood2) The calculation formula is as follows:
W2(MPa) maximum load force (N) of glue line fracture/glue joint area (mm)2)
The test results are shown in table 1 below.
TABLE 1
The results in table 1 show that the adhesive prepared by adding unmodified wood fibers in comparative example 2 has slightly stronger bonding strength than the adhesive prepared by adding no wood fibers in comparative example 1; the adhesive prepared by adding the modified wood fiber in the examples 1-4 has obviously improved bonding strength compared with the adhesive added with unmodified fiber (comparative example 2), and the trial period of the adhesive is also improved.
Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.