CN114426779A - Tannin biomimetic cross-linking-based all-biomass wood-bamboo composite material and preparation method thereof - Google Patents

Abstract

The invention discloses a tannin biomimetic cross-linking based full-biomass wood-bamboo composite material and a preparation method thereof, wherein the preparation method comprises the following steps: coating tannin-based bionic wood adhesive based on phenol-amine synergy on the surface of wood and bamboo or veneers, or uniformly mixing with wood and bamboo structural units, and then preparing the tannin bionic cross-linking-based full-biomass wood-bamboo composite material according to the conventional wood-bamboo composite material manufacturing process parameters. The tannin biomass adhesive with the bionic crosslinking characteristic is simple in preparation process, low in price and easy to obtain raw materials, and environment-friendly in production and use processes, and the prepared wood-bamboo composite materials such as wood-bamboo glued products, laminated wood and artificial boards have the characteristics of high gluing strength, excellent water resistance, no formaldehyde release and the like.

Description

A kind of whole biomass wood-bamboo composite material based on tannin biomimetic cross-linking and preparation method thereof

technical field

The invention relates to the field of wood-bamboo biomass composite materials, in particular to a full biomass wood-bamboo composite material based on biomimetic cross-linking of tannins and a preparation method thereof.

Background technique

Wood-bamboo composite materials use renewable wood and bamboo as the basic raw materials, usually with a certain synthetic resin adhesive, and are prepared under hot pressing conditions. They are mainly used for home manufacturing and interior decoration, and are closely related to people's lives.

Synthetic resin adhesives play an important role in the preparation of wood-bamboo composite materials and determine the quality and performance of products. Among them, formaldehyde series resins, including urea-formaldehyde resins, phenolic resins and melamine-formaldehyde resins, are the most important adhesives at present, with excellent performance and low cost, but they have been criticized due to the defect of formaldehyde release. In order to eliminate the formaldehyde release of wood-bamboo composite materials, isocyanate-based adhesives have been applied, but the following deficiencies exist in the use of isocyanate-based adhesives: 1) The price of isocyanates is usually about 5 times that of formaldehyde series resins, and the production cost is high; 2) The use of isocyanates to produce wood-based panels is prone to problems such as sticking and hot pressing, and it is necessary to use a release agent; 3) isocyanates are easy to react with water, so the metering and pumping systems cannot have water. Poor system compatibility; 4) Isocyanate monomers are highly toxic and usually need to be produced in a fully enclosed environment. Affected by the above factors, the market share of isocyanate-based adhesives in the field of wood-bamboo composite materials in my country has always been small.

Biomass adhesives are currently a hot spot of concern. Among them, tannin-based adhesives have been industrialized in some countries. Scientists in my country have also carried out fruitful work on the structural modification and product development of tannins. However, the adhesives prepared solely with tannins still have shortcomings such as low bonding strength and poor water resistance.

As a natural polyphenolic substance, tannin widely exists in various tissues of various plants. The structure of tannin is complex and diverse, and it contains a large number of active groups such as phenolic hydroxyl groups. These groups are used in traditional tannin adhesives. In the preparation process of the agent, it is not used reasonably and leads to defects such as poor water resistance of the glued products. There is still a lot of room for making full use of the structural advantages of tannins to prepare tannin-based adhesives with high bonding strength, excellent water resistance and environmental friendliness.

At present, there is a lack of an environmentally safe and biomimetic cross-linked tannin-based all-biomass wood-bamboo composite material and its preparation method.

SUMMARY OF THE INVENTION

In view of the above-mentioned defects of the prior art, the present invention provides an environment-friendly and safe all-biomass wood-bamboo composite material based on biomimetic cross-linking of tannins and a preparation method thereof.

In order to solve the problems of the prior art, the present invention achieves the above object through the following technical solutions: a kind of biomimetic cross-linked tannin-based full biomass wood-bamboo composite material of the present invention; The chemical structural formula of the biomass wood-bamboo composite material is shown in formula (I):

A preparation method of a tannin biomimetic cross-linked full biomass wood-bamboo composite material of the present invention comprises the following steps: coating the tannin-based biomimetic wood adhesive based on phenolamine synergy on the surface of wood, bamboo or veneer , or evenly mixed with the wood-bamboo structural units, and then according to the conventional wood-bamboo composite material manufacturing process parameters, the full biomass wood-bamboo composite material based on tannin biomimetic cross-linking is obtained. The wood and bamboo structural units are fibers or shavings.

The preparation method of the tannin-based biomimetic wood adhesive based on phenolamine synergy according to the present invention comprises the following steps:

(1) first tannin concentrate is oxidized with hydrogen peroxide H ₂ O ₂ to obtain a tannin concentrate rich in benzoquinone functional groups;

(2) uniformly mixing the tannin concentrate prepared in step (1) with the sodium hydroxide NaOH solution, and adjusting the pH of the mixture to 6.0-8.0 to obtain a tannin mixture;

(3) blending the tannin mixture prepared in the step (2) with the hyperbranched polyamine in a ratio of 1:0.1-0.9 by absolute dry weight, and realizing cross-linking of small tannins through the biomimetic principle of insect epidermis hardening, Tannin-based biomimetic wood adhesive based on phenolamine synergy was prepared by Schiff base reaction.

Further, in step (1), the absolute dry weight ratio of hydrogen peroxide to tannin concentrate is 1:20-100.

Further, in step (3), the prepared tannin-based biomimetic wood adhesive based on phenolamine synergy has a solution solid content of 20% to 65%.

Further, in step (3), the preparation method of hyperbranched polyamine: first react ethylenediamine, diethylenetriamine, triethylenetetramine and other polyethylene polyamines with methyl acrylate, and then react with ethylene diamine. Amine reaction synthesis to obtain hyperbranched polyamines. The invention realizes high cross-linking by synthesizing polyamines with hyperbranched structure, and ensures that the cured resin can form a dense network structure so as to improve the gluing performance of the resin.

Hyperbranched polyamines include, but are not limited to, ethylenediamine, diethylenetriamine, triethylenetetramine and other polyethylene polyamines are synthesized and prepared in two steps, and hyperbranched polyamines are synthesized in two steps. , diethylene triamine, triethylene tetraamine or other polyethylene polyamines react with methyl acrylate to synthesize hyperbranched skeletons, and then react with ethylenediamine to obtain polyamines with hyperbranched structures.

Further, in step (3), the curing process is biomimetic cross-linking, and the degree of cross-linking can be achieved by adjusting the ratio of the tannin mixture to the hyperbranched polyamine. 2 to 8 minutes. The invention provides a biomimetic cross-linking method of tannin. Under the action of phenol oxidase and oxygen, the phenolic compounds contained in the cuticle of insects react with amino groups on proteins to form cuticle finally. The mechanism of this process is the synergistic reaction of phenolamines. Inspired by the hardening of the cuticle of insects, in the present invention, tannins are oxidized to convert a large number of phenolic hydroxyl groups into quinones, which are then reacted with polyamines to achieve cross-linking.

Beneficial effects: the tannin-based biomass adhesive with biomimetic cross-linking characteristics used in the present invention has a simple preparation process, a wide range of raw material sources, cheap and easy-to-obtain raw materials, high efficiency, environmentally friendly production and use processes, and environmental protection and safety. The wood-bamboo laminated products, laminated wood and wood-based panels and other wood-bamboo composite materials have the characteristics of high bonding strength, excellent water resistance, and no formaldehyde release.

Compared with the prior art, the present invention has the following advantages: (1) the present invention utilizes the oxidation of tannins to generate highly active benzoquinone, which can react rapidly with hyperbranched polyamines at room temperature, resulting in high bonding strength and excellent water resistance. And environmentally friendly biomimetic adhesives.

(2) The wood-bamboo composite material prepared by the present invention can realize controllable performance by adjusting the amount of tannin, and at the same time, the curing can be reduced to less than 120 ° C. Compared with the existing biomass adhesive, the energy consumption is reduced, and the prospects for industrial application.

(3) Tannin-type biomass adhesive is used in the manufacturing process of the present invention, and the curing process is biomimetic cross-linking, allowing a large number of active groups such as phenolic hydroxyl groups to participate in the curing reaction, thereby significantly improving the performance of the wood-bamboo composite material. Tannin is the backbone of the adhesive resin, and tannin is also derived from nature, so it helps to realize the full biomass production of wood-bamboo composite materials.

(4) Lee et al. discovered the synergistic effect of phenol-amines in the process of epidermal sclerosis of insects. Inspired by this discovery, the present invention realizes tannins by simply treating tannins and introducing synergistic reactions of phenol-amines. The biomimetic cross-linking of the adhesive significantly improves the physical and mechanical properties and water resistance of the adhesive.

Description of drawings

Fig. 1 is the chemical structural formula of the tannin biomimetic wood adhesive based on the synergistic cross-linking network of phenolamines of the present invention.

Fig. 2 is a chemical structure diagram of branched polyamines (PA _4N , PA _5N , PA _6N , PA _7N ) of the present invention.

Detailed ways

The following examples will specifically illustrate the content of the present invention, but the present invention is not limited thereto. Modifications or substitutions made to the methods, steps or conditions of the present invention without departing from the spirit and essence of the present invention all belong to the scope of the present invention.

Example 1

As shown in Figure 1 and Figure 2, a biomimetic cross-linked tannin-based full biomass wood-bamboo composite material of the present invention is characterized in that: the tannin-based biomimetic cross-linked full biomass wood-bamboo composite material The chemical structural formula of is shown in formula (I):

A preparation method of a tannin biomimetic cross-linked full biomass wood-bamboo composite material of the present invention comprises the following steps: coating the tannin-based biomimetic wood adhesive based on phenolamine synergy on the surface of wood, bamboo or veneer , or evenly mixed with the wood-bamboo structural units, and then according to the conventional wood-bamboo composite material manufacturing process parameters, the full biomass wood-bamboo composite material based on tannin biomimetic cross-linking is obtained. The wood and bamboo structural units are fibers or shavings.

The preparation method of the tannin-based biomimetic wood adhesive based on phenolamine synergy according to the present invention comprises the following steps:

(1) first tannin concentrated solution is oxidized with hydrogen peroxide H ₂ O ₂ to obtain the tannin concentrated solution rich in benzoquinone functional group; the absolute dry weight ratio of hydrogen peroxide and tannin concentrated solution is 1: 20 to 100.

(2) uniformly mixing the tannin concentrate prepared in step (1) with the sodium hydroxide NaOH solution, and adjusting the pH of the mixture to 6.0-8.0 to obtain a tannin mixture;

(3) blending the tannin mixture prepared in the step (2) with the hyperbranched polyamine in a ratio of 1:0.1-0.9 by absolute dry weight, and realizing cross-linking of small tannins through the biomimetic principle of insect epidermis hardening, Tannin-based biomimetic wood adhesive based on phenolamine synergy was prepared by Schiff base reaction.

The curing process is biomimetic cross-linking, and the degree of cross-linking can be achieved by adjusting the ratio of the tannin mixture to the hyperbranched polyamine.

Example 1

A method for preparing a biomimetic cross-linked tannin-based full biomass wood-bamboo composite material comprises the following steps:

(1) take by weighing the tannin concentrate of 5g, add the tannin concentrate to the hydrogen peroxide H ₂ O ₂ aqueous solution, and the add-on of the hydrogen peroxide H ₂ O ₂ aqueous solution is 5% of the total volume;

(2) Mix the tannin concentrate prepared in step (1) with the sodium hydroxide solution uniformly, and adjust the pH of the mixed solution to 7.0.

(3) adding 5g of hyperbranched polyamine PA _6N to the tannin mixed solution obtained in step (2) and blending and stirring rapidly for 30min to obtain a solid content of 50%. The tannin mixed solution and The mass ratio of hyperbranched polyamines to dryness is 1:1. The cross-linking of small tannins is achieved through the biomimetic principle of insect epidermis hardening. Through the Schiff base reaction, a tannin-based biomimetic wood adhesive based on phenolamine synergy is prepared. .

The solution solid content of the phenolamine-based tannin-based biomimetic wood adhesive is 20% to 65%. The preparation method of hyperbranched polyamine: firstly, ethylenediamine, diethylenetriamine, triethylenetetramine and other polyethylenepolyamines are reacted with methyl acrylate, and then reacted with ethylenediamine to synthesize the hyperbranched polyamine.

The tannin-based biomimetic wood adhesive prepared in step (3) was applied on a plywood for pressing, and one side was sizing, the sizing amount was 200 g/m ² , the hot pressing temperature was 120° C., and the heat was applied to the plywood. The pressing time is 6 minutes, and the bonding strength and water resistance of the plywood are tested according to the requirements of the national standard GB/T17657-2013 "Test methods for physical and chemical properties of wood-based panels and veneer wood-based panels".

Example 2

The difference between Example 2 and Example 1 is: in step (3), at normal temperature, 10g of hyperbranched polyamine PA _6N is added to the tannin mixed solution obtained in step (2) of Example 1 to blend and rapidly. Stir for 30min to obtain a solid content of 50%, the tannin mixed solution and the hyperbranched polyamine in a dry mass ratio of 1:2 to obtain a tannin-based biomimetic wood adhesive based on phenolamine synergy .

Example 3

The difference between Example 3 and Example 1 is: in step (3), at normal temperature, to the tannin solution obtained in step (2) of Example 1, add 5g of hyperbranched polyamine PA _6N to blend and rapidly. Stir for 30min to obtain a solid content of 40%, the tannin mixed solution and the hyperbranched polyamine in a dry mass ratio of 1:1 to obtain a tannin-based biomimetic wood adhesive based on phenolamine synergy .

Example 4

The difference between embodiment 4 and embodiment 1 is: in step (3), at normal temperature, to the tannin solution obtained in step (2) of embodiment 1, add 5g of hyperbranched polyamine PA _6N to blend and rapidly. Stir for 30min to obtain a solid content of 30%, the tannin mixed solution and the hyperbranched polyamine in a dry mass ratio of 1:1, to obtain a tannin-based biomimetic wood adhesive based on phenolamine synergy .

Example 5

The difference between Example 5 and Example 1 is: in step (3), at normal temperature, to the tannin solution obtained in step (2) of Example 1, add 5g of hyperbranched polyamine PA _5N to blend and rapidly. Stir for 30min to obtain a solid content of 40%, the tannin mixed solution and the hyperbranched polyamine in a dry mass ratio of 1:1 to obtain a tannin-based biomimetic wood adhesive based on phenolamine synergy .

Example 6

The difference between Example 6 and Example 1 is: in step (3), at normal temperature, to the tannin solution obtained in step (2) of Example 1, add 5g of hyperbranched polyamine PA _4N to blend and rapidly. Stir for 30min to obtain a solid content of 40%, the tannin mixed solution and the hyperbranched polyamine in a dry mass ratio of 1:1 to obtain a tannin-based biomimetic wood adhesive based on phenolamine synergy.

Take the tannin-based biomimetic wood adhesive based on phenolamine synergy prepared in the embodiment to press the three-layer plywood, according to the requirements of the national standard GB/T 17657-2013 "Physicochemical Performance Test Method for Wood-based Panels and Finished Wood-based Panels", The test results were respectively tested on the universal mechanical testing machine for bonding strength 1 (dry strength), bonding strength 2 (soak the test piece in 63°C water for 3 hours), and bonding strength 3 (soak the test piece in boiling water for 3 hours). As shown in Table 1.

Table 1

Example Bonding strength 1 (MPa) Bonding strength 2 (MPa) Bonding strength 3(MPa) Example 1 1.90 1.37 1.24 Example 2 1.93 1.54 0.80 Example 3 1.90 1.38 1.12 Example 4 2.15 0.80 0.72 Example 5 2.16 2.29 1.04 Example 6 1.44 1.13 0.84

As shown in Table 1, according to the measured bonding strength of Example 1 to Example 6, the analysis was carried out. After screening, it was obtained: when the mass ratio of tannin to hyperbranched polyamine PA _5N was 1:1, the overall solid content was At 40%, the best plywood gluing data were obtained. It indicated that the phenolamine synergistic network of tannins and hyperbranched polyamines was successfully constructed.

As described above, the present invention has been described through description and specific embodiments. On the basis of the present invention, any person skilled in the art who is familiar with the technical field of the present invention can, within the technical scope disclosed by the present invention, follow the technical solutions of the present invention and the inventive concept thereof. Equivalent replacements or changes should be included within the protection scope of the present invention.

Claims (7)

1. The utility model provides a full living beings wood bamboo combined material based on bionical cross-linking of tannin which characterized in that: the chemical structural formula of the tannin biomimetic cross-linked full-biomass wood-bamboo composite material is shown as the formula (I):

2. the method for preparing the tannin biomimetic cross-linked based full-biomass wood-bamboo composite material in claim 1, is characterized by comprising the following steps:

coating tannin-based bionic wood adhesive based on phenol-amine synergy on the surface of wood and bamboo or a veneer, or uniformly mixing the wood and bamboo structural units, and then preparing the tannin bionic cross-linked full-biomass wood-bamboo composite material according to the conventional wood-bamboo composite material manufacturing process parameters; the wood-bamboo structural unit is fiber or wood shavings.

3. The method for preparing the tannin based bionic wood adhesive based on phenol amine synergy as claimed in claim 2, is characterized by comprising the following steps:

(1) firstly, the concentrated tannin solution is treated with hydrogen peroxide H₂O₂Carrying out oxidation treatment to obtain tannin concentrated solution rich in benzoquinone functional groups;

(2) uniformly mixing the tannin concentrated solution prepared in the step (1) with a sodium hydroxide NaOH solution, and adjusting the pH of the mixed solution to 6.0-8.0 to prepare a tannin mixed solution;

(3) and (3) blending the tannin mixed solution prepared in the step (2) with hyperbranched polyamine according to the absolute dry weight ratio of 1: 0.1-0.9, realizing tannin small molecule crosslinking by an insect epidermis hardening bionic principle, and preparing the tannin-based bionic wood adhesive based on phenol-amine synergy by Schiff base reaction.

4. The method for preparing the tannin based bionic wood adhesive based on phenol amine synergy according to claim 3, wherein the method comprises the following steps: in the step (1), the absolute dry weight ratio of the hydrogen peroxide to the tannin concentrated solution is 1: 20-100.

5. The method for preparing the tannin based bionic wood adhesive based on phenol amine synergy according to claim 3, wherein the method comprises the following steps: in the step (3), the solution solid content of the prepared tannin-based bionic wood adhesive based on phenol-amine synergy is 20-65%.

6. The method for preparing the tannin based bionic wood adhesive based on phenol amine synergy according to claim 3, wherein the method comprises the following steps: in the step (3), the preparation method of the hyperbranched polyamine comprises the following steps: firstly, ethylenediamine, diethylenetriamine, triethylenetetramine and other polyethylene polyamines react with methyl acrylate, and then react with ethylenediamine to synthesize the hyperbranched polyamine.

7. The method for preparing the tannin based bionic wood adhesive based on phenol amine synergy according to claim 3, wherein the method comprises the following steps: in the step (3), the curing process is bionic crosslinking, the crosslinking degree can be realized by adjusting the proportion of the tannin mixed solution and the hyperbranched polyamine, the hot-pressing curing temperature is 100-160 ℃, and the hot-pressing time is 2-8 minutes.

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