CN110587744B

CN110587744B - Preparation method of complex wood

Info

Publication number: CN110587744B
Application number: CN201910889970.4A
Authority: CN
Inventors: 余养伦; 于文吉; 张耀明; 闫昊鹏
Original assignee: Research Institute of Wood Industry of Chinese Academy of Forestry
Current assignee: Research Institute of Wood Industry of Chinese Academy of Forestry
Priority date: 2019-09-20
Filing date: 2019-09-20
Publication date: 2021-04-23
Anticipated expiration: 2039-09-20
Also published as: CN110587744A

Abstract

The invention relates to a preparation method of complex wood, and belongs to the technical field of wood processing. The preparation method of the complex wood comprises the following steps: step 1: preparing a proper amount of wood; step 2: introducing plant polyphenol into wood to obtain polyphenol wood; and step 3: introducing metal salt into the polyphenol wood to obtain polyphenol metal salt wood; and 4, step 4: and drying the polyphenol metal salt wood to obtain the complex wood. The invention introduces a dynamic multi-sacrifice bond network structure of 'cellulose-plant polyphenol-metal salt' into wood to support cellulose and/or hemicellulose, so that the dynamic multi-sacrifice bond network structure reduces or even does not generate expansion or shrinkage when absorbing or desorbing moisture, simultaneously dissipates a large amount of energy in a wood material system under the dynamic action of continuous fracture and reconstruction of sacrifice bonds, eliminates or weakens internal stress, protects the integrity of a cellulose skeleton covalent bond network, and provides a new method for solving the cracking problem of wood.

Description

Preparation method of complex wood

Technical Field

The invention relates to the technical field of wood processing, in particular to a preparation method of complex wood.

Background

Along with the technological progress and social development, the demand of human beings on wood is larger and larger, the application range is wider and wider, and the required quality is higher and higher. However, the lack of forest resources in China and the inherent properties of wood make wood materials difficult to meet the increasing market demands in the fields of products and applications. The wood functional improvement technology aims at improving the quality of wood materials, endows the wood materials with new performance, expands the application range of the wood materials and becomes an important component part for sustainable development of the society and the economy in China.

Wood materials and wood products have outstanding properties such as environmental properties-visual, tactile, auditory, olfactory and regulatory properties of wood, material properties-processability, high strength to weight ratio, thermal and electrical insulation, biological functions-renewability and degradability-which are well recognized by mankind, but their application is limited by swelling and drying shrinkage, cracking and deformation, decay and mildew, discoloration and the like.

In the prior art, in order to prevent cracking of wood, a wood modification solution is generally used, for example, patent CN106182249A discloses a preparation method of high-strength wood with sterilization and cracking prevention, belonging to the technical field of wood treatment. The method comprises the steps of boiling wood, placing the wood into a pressure tank for blasting treatment, drying the wood after treatment to control the water content, soaking the wood in a wood modification solution, taking the soaked wood out, drying the wood, uniformly spraying a nano silica sol modified by hexadecyl trimethoxy silane on the surface of the wood, and drying the wood after spraying, wherein the wood modification solution is prepared by extracting and concentrating lily leaves and tea seed meal and preparing the allyl glycidyl ether, dimethyl acetamide, diethylene glycol, sodium hydroxide, diammonium hydrogen phosphate, cyproconazole and the like.

Aiming at the main defects of the wood in the using process, people adopt physical and chemical technologies to carry out functional improvement, and the functional improvement comprises a wood strengthening technology, a wood size stability enhancing technology, a wood anticorrosion and mildew-proof technology, a wood discoloration prevention and dyeing technology and the like.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a preparation method of complex wood; the complex wood prepared by the method has the advantages of cracking reduction, even no cracking, stable size and the like.

In order to solve the technical problems, the invention provides the following technical scheme:

the invention provides a preparation method of complex wood, which comprises the following steps:

step 1: preparing a proper amount of wood;

step 2: introducing plant polyphenol into wood to obtain polyphenol wood;

and step 3: introducing metal salt into the polyphenol wood to obtain polyphenol metal salt wood;

and 4, step 4: and drying the polyphenol metal salt wood to obtain the complex wood.

Preferably, the absolute water content of the wood is 6-300%.

Further, the step 2 is as follows:

21) dissolving plant polyphenol in water, and stirring uniformly to form a plant polyphenol water solution;

22) soaking the wood in plant polyphenol water solution to introduce plant polyphenol into cell cavity, cell wall or cell gap;

23) drying the wood impregnated with the aqueous solution of plant polyphenols to form a polyphenol wood.

Further, the concentration of the plant polyphenol water solution is 1-250 g/L, the average molecular weight is 170-50000, and the plant polyphenol water solution is 1-40 polymers; the ratio of plant polyphenol to wood is as follows: 0% -15%; the impregnation time of the wood in the plant polyphenol water solution is 10min-48h, the impregnation temperature is 0-80 ℃, and the impregnation method is normal pressure, pressurization or pressurization after vacuum pumping.

Preferably, the plant polyphenol is one or more of tannin extract, tannin, tannic acid, terminal food acid and pyrogen terminal food acid.

Further, the step 3 is:

31) dissolving metal salt in the aqueous solution, and stirring uniformly to form a metal salt aqueous solution;

32) immersing the polyphenol wood in a metal salt aqueous solution to introduce metal ions into the cell cavities, cell walls or intercellular spaces.

Further, the concentration of the metal salt water solution is 0.3 g/L-300 g/L; the ratio of the metal salt to wood is as follows: 0.1% -12%; the wood is soaked in the metal salt water solution for 10min to 180 days at the soaking temperature of 0 to 80 ℃, and the soaking method is normal pressure, pressurization or pressurization after vacuum pumping.

Preferably, the metal salt is one or more of iron salt, copper salt, aluminum salt, titanium salt, calcium salt, molybdenum salt, tungsten salt, chromium salt, magnesium salt, potassium salt and double salts thereof, and the pH value of the aqueous solution of the metal salt is 3.5-4.5.

Preferably, the absolute water content of the dried polyphenol metal salt wood is 25-50%, and then the oxygen content in the air is adjusted to 22-50% until the absolute water content of the polyphenol metal salt wood is 6-12%.

The existing research considers that the causes of wood cracking are many, and the main factor is that polysaccharides (cellulose, hemicellulose and other substances) in wood absorb or release water in the processes of moisture absorption and desorption to cause wood expansion or shrinkage, so that the wood is unstable in size and cracks.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, plant polyphenol and metal salt are introduced into the cell wall of wood, phenolic hydroxyl groups of the plant polyphenol are combined with hydroxyl groups of cellulose and hemicellulose, and meanwhile, ortho-position phenolic hydroxyl groups are complexed with metal ions to crosslink adjacent molecular chains of the cellulose/hemicellulose into a net structure, just as if a plurality of supports are supported on the molecular chains of the cellulose/hemicellulose, the expansion or contraction of the molecular chains is reduced or even not generated during moisture absorption or desorption; on the basis of the above, a large number of multiple sacrificial bond networks consisting of hydrogen bonds (the plant polyphenol phenolic hydroxyl groups are combined with the hydroxyl groups in the wood to form multi-point hydrogen bonds) and coordination bonds (the ortho hydroxyl groups on the plant polyphenol phenolic rings are complexed with metal salts to form coordination bonds) are formed in the cellulose skeleton. Because the sacrificial bond energy is less than the covalent bond (covalent bond network is formed between cellulose, hemicellulose, lignin and phenolic resin), the sacrificial bond is broken in preference to the covalent bond when the wood is subjected to internal stress or external force. The dynamic action of the continuous breakage and reconstruction of the sacrificial bonds dissipates a large amount of energy in a wood system, eliminates or weakens internal stress, and protects the integrity of a cellulose skeleton covalent bond network. This provides a new approach to the problem of wood cracking.

Firstly, introducing plant polyphenol into wood to swell the wood; then introducing metal salt into the wood, combining plant polyphenol with cellulose and hemicellulose in the wood to form a multi-point hydrogen bond, complexing the plant polyphenol with the metal salt, and combining the cellulose-plant polyphenol-metal salt into a whole just like forming a plurality of support supports in cellulose skeleton molecules; then, accompanied by evaporation and oxidation reactions of water, the "cellulose-plant polyphenol-metal salt" is further cross-linked and oxidized, finally forming a complex wood. The dynamic multi-sacrifice bond network structure of the invention 'cellulose-plant polyphenol-metal salt' supports cellulose and/or hemicellulose, so that the expansion or shrinkage of the structure is reduced or even not generated when the structure absorbs moisture or desorbs, and simultaneously, under the dynamic action of continuous fracture and reconstruction of sacrifice bonds, a great deal of energy in a wood recombination material system is dissipated, the internal stress is eliminated or weakened, the integrity of a cellulose skeleton covalent bond network is protected, and the problem of easy cracking of wood is solved from the molecular level.

Drawings

FIG. 1 is a diagram of a dry shrinkage and wet swelling molecular chain of a cell wall cellulose skeleton in the prior art;

FIG. 2 is a molecular chain structure diagram of the complex wood cellulose framework in dry and wet states;

FIG. 3 shows the condition of lignum Pini nodi before and after treatment in example 1;

FIG. 4 is a comparative graph of oak treatment in example 2 of the present invention;

FIG. 5 is a graph of catalpa bungei before and after complexation in example 3 of the present invention;

FIG. 6 is a graph of complexed pre-and post-quercus acutissima veneers in example 5 of the present invention;

FIG. 7 is a graph comparing the contact angles of complexed pre-and post-quercus acutissima veneers in example 5 of the present invention.

Detailed Description

In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following detailed description is given with reference to specific embodiments.

In the present invention, the materials and reagents used are not specifically described, and are commercially available.

Example 1

A method of making a complexed wood comprising:

step 1: preparing a proper amount of wood

Cutting lignum Pini nodi with length of 200cm, sawing, processing into sawn timber with certain specification, and drying to control absolute water content at 6%;

step 2: introducing black wattle bark tannin into wood

Dissolving black wattle bark tannin in water, and stirring uniformly to form a semi-colloidal aqueous solution with coexisting molecular dispersion state and molecular aggregation state, wherein the concentration is 20 g/L;

then, soaking the wood prepared in the step 1 in the black wattle bark tannin solution; adopting hydraulic pressure to carry out impregnation for 12h, wherein the impregnation temperature is 25 ℃, and the pressure is 1.2MPa, introducing plant polyphenol into a cell cavity, a cell wall or a cell gap, controlling the impregnation amount of tannin to be 3% of the mass of wood through hydraulic pressure flow, taking out the wood, placing the wood in a drying kiln to be dried, gradually evaporating the water in the wood, controlling the water content of the wood, and taking out the wood when the absolute water content is 80% to form the polyphenol wood;

and step 3: introduction of metal salts into polyphenolic wood

Dissolving aluminum sulfate in the aqueous solution, and uniformly stirring to form an aluminum sulfate aqueous solution with the concentration of 0.3 g/L;

soaking the polyphenol wood prepared in the step 2 in the aluminum sulfate aqueous solution prepared in the step 3 for 12h at the temperature of 25 ℃, adopting hydraulic pressure to pressurize and soak, wherein the pressure is 1.2MPa, introducing the aluminum sulfate aqueous solution into a cell cavity, a cell wall or a cell gap, controlling the impregnation amount of aluminum sulfate to be 1.5% of the mass of the wood through hydraulic pressure, and taking out the wood to form polyphenol aluminum salt wood;

and 4, step 4: dried polyphenol aluminum salt wood

And placing the wood in a drying kiln, gradually evaporating the moisture in the wood by adopting a conventional drying method, and taking out the wood when the absolute moisture content is 12% to obtain the complex wood.

The existing research considers that the causes of wood cracking are many, and the main factor is that polysaccharides (cellulose, hemicellulose and the like) in wood absorb or release water in the processes of moisture absorption and desorption to cause wood expansion or contraction, as shown in figure 1, so that the wood is unstable in size and cracked.

According to the invention, plant polyphenol and metal salt are introduced into the cell wall of the wood recombinant material, phenolic hydroxyl groups of the plant polyphenol are combined with hydroxyl groups of cellulose and hemicellulose, meanwhile, ortho phenolic hydroxyl groups are complexed with metal ions, and molecular chains of adjacent cellulose/hemicellulose are crosslinked into a net structure, as if a plurality of supports are supported on the molecular chains of the cellulose/hemicellulose, so that the expansion or contraction of the molecular chains is reduced or even not generated during moisture absorption or desorption, as shown in figure 2.

Comparing the complex wood obtained by the method of the embodiment before and after the treatment, it can be seen from fig. 3 that the untreated wood has more cracks, and the complex wood obtained after the treatment has no cracks on the surface and has higher stability.

Meanwhile, the physical and mechanical properties of the wood before and after the treatment are measured, as shown in table 1, as can be seen from table 1, the air-dried density, strength and elastic modulus of the material are increased after the complexing treatment; the dimensional stability is greatly improved; the turpentine oil is fixed in the wood and does not drift to the surface of the material, as shown in fig. 3.

TABLE 1 comparison of Properties of Pinus nutans before and after complexing treatment

Performance index	Without complexing treatment	Complexing treatment
			Air-dried Density (g/cm)³)	0.43	0.48
Flexural Strength (MPa)	59.2	68.2
			Modulus of elasticity (GPa)	9.2	9.7
Radial dry shrinkage factor (%)	0.15	0.04
			Chord dry shrinkage factor (%)	0.33	0.08

Example 2

A method of making a complexed wood comprising:

step 1: preparing proper amount of log

Cutting fresh quercus acutissima into wood sections with the length of 300cm, and removing barks to obtain quercus acutissima logs;

step 2: introducing polyphenol into Quercus acutissima

Dissolving valonea extract in water solution, and stirring to obtain semi-colloidal water solution with both molecular dispersion state and molecular aggregation state, wherein the concentration is 2.0 g/L;

then soaking the quercus acutissima logs prepared in the step 1 in the valonea extract solution; adopting pressure impregnation, wherein the impregnation time is 24h, the temperature is 25 ℃, and the pressure is 1.8MPa, introducing the valonea extract aqueous solution into a cell cavity, a cell wall or a cell gap, taking out the quercus acutissima, placing the quercus acutissima in a drying kiln or air, gradually evaporating the water in the quercus acutissima, and taking out the quercus acutissima when the absolute water content of the quercus acutissima is 12% to form polyphenol quercus acutissima;

and step 3: introducing metal salt into the above polyphenol Quercus acutissima

Dissolving ferrous chloride in an aqueous solution, and uniformly stirring to obtain a ferrous chloride salt solution with the concentration of 30 g/L;

soaking the polyphenol wood prepared in the step 2 in the ferrous chloride solution prepared in the step 3 for 60 days at room temperature by adopting normal-pressure soaking to obtain polyphenol ferrous chloride oak;

and 4, step 4: dried polyphenol ferrous chloride oak

And placing the wood in a drying kiln to gradually evaporate water in the polyphenol ferrous chloride oak, introducing oxygen when the absolute moisture content of the polyphenol ferrous chloride oak is 50%, so that the oxygen content of the medium in the drying kiln reaches 30%, and recovering the oxygen content of the medium in the drying kiln to a normal level when the absolute moisture content of the polyphenol ferrous chloride oak is 30%, until the absolute moisture content is 6-12%, so as to obtain the complex wood.

Before and after the wood treatment in this example, as shown in fig. 4, the complex wood obtained by the method of the present invention has no crack on the surface and good wood stability.

The physical and mechanical properties of the wood before and after the treatment were also measured, as shown in table 2. As can be seen from Table 2, after the complexing treatment, the density, the strength and the elastic modulus of the material are increased to a certain extent, and the radial dry shrinkage coefficient and the chord dry shrinkage coefficient are greatly reduced, namely the dimensional stability is greatly increased.

TABLE 2 comparison of Performance of pre-and post-complexation treated Quercus acutissima

Performance index	Untreated	Complexing treatment
			Air-dried Density (g/cm)³)	0.65	0.69
Flexural Strength (MPa)	128.9	137.8
			Modulus of elasticity (GPa)	16.8	17.2
Radial dry shrinkage factor (%)	0.21	0.04
			Chord dry shrinkage factor (%)	0.40	0.07

Example 3

A method of making a complexed wood comprising:

step 1: preparing appropriate amount of fructus Sorbi Pohuashanensis

Cutting the catalpa bungei into wood sections with the length of 200cm, processing the wood sections into sawn timber with a certain specification after sawing, and controlling the absolute water content to be 6 percent after drying;

step 2: introducing polyphenol into catalpa bungei

Dissolving the Marxist tannin extract in an aqueous solution, and uniformly stirring to form a semi-colloidal aqueous solution with coexisting molecular dispersion state and molecular aggregation state, wherein the concentration is 0.3 g/L;

then, soaking the catalpa bungei sawn timber prepared in the step 1 in the Mabushi tannin extract solution; soaking for 4h at 25 deg.C under 12MPa under pressure to make the wood amount of the extract solution 0.3%, taking out, placing in a drying kiln or air, gradually evaporating water, and taking out when the absolute water content of fructus Sorbi Pohuashanensis is 48% to obtain polyphenol fructus Sorbi Pohuashanensis sawn wood;

and step 3: introducing ferric chloride into the saw material of polyphenol catalpa bungei

Uniformly stirring ferric chloride in the aqueous solution to form a ferric chloride aqueous solution with the concentration of 0.3 g/L;

soaking the polyphenol catalpa bungei prepared in the step 2 in the ferric chloride solution prepared in the step 3 for 12h at 40 ℃ under the pressure of 1.6MPa by adopting hydraulic soaking, wherein the soaking amount of the ferric chloride is 3 percent of the mass of the wood, and taking out the catalpa bungei wood to obtain the polyphenol iron chloride catalpa bungei;

and 4, step 4: dried polyphenol Sorbus pohuashanensis (lour.) Merr

Placing in a drying kiln at 60 deg.C to gradually evaporate water to an absolute water content of 10-12% to obtain complex wood, as shown in FIG. 5.

TABLE 3 comparison of Catalpa bungei Performance before and after complexation treatment

Performance index	Without complexing treatment	Complexing treatment
			Air-dried Density (g/cm)³)	0.52	0.55
Flexural Strength (MPa)	98.8	104.8
			Modulus of elasticity (GPa)	10.3	10.5
Radial dry shrinkage factor (%)	0.10	0.03
			Chord dry shrinkage factor (%)	0.23	0.06

The physical and mechanical properties of the wood before and after the treatment were also measured, as shown in table 3. As can be seen from Table 3, after the complexing treatment, the density, the bending strength and the modulus of the material are improved to a certain extent, and the radial dry shrinkage coefficient and the chord dry shrinkage coefficient are greatly reduced, namely the dimensional stability is greatly increased.

Example 4

A method of making a complexed wood comprising:

step 1: preparing proper amount of poplar sawn timber

Cutting poplar into wood sections with the length of 200cm, processing the cut poplar into sawn timber with a certain specification after sawing, and controlling the water content to be 15% after drying;

step 2: introducing polyphenol into poplar

Dissolving tannic acid in water, and stirring to obtain tannic acid water solution with concentration of 3 g/L;

then, soaking the poplar sawn timber prepared in the step 1 in the tannic acid solution; soaking for 2h at 25 deg.C under 0.3MPa to make tannin amount to 2.5% of poplar sawn timber, taking out the poplar sawn timber, placing in air to gradually evaporate water in the poplar sawn timber, and taking out when absolute water content is 50% to obtain poplar polyphenol sawn timber;

and step 3: introducing zinc borate and ammonia soluble alkylamine copper into poplar polyphenol sawn timber

Zinc borate and copper ammonia soluble Alkylamine (ACQ) were added in a ratio of 1: 1 proportion in the water solution, and after stirring uniformly, forming a copper-zinc mixed metal salt water solution with the concentration of 1.5 g/L;

soaking the polyphenol poplar prepared in the step 2 in the copper-zinc mixed metal salt solution prepared in the step 3 for 2 hours at 25 ℃, soaking by adopting hydraulic pressure at 0.4MPa to ensure that the soaking amount of the copper-zinc mixed metal salt is 3.2 percent of the mass of the wood, and taking out the polyphenol poplar to obtain the polyphenol copper-zinc mixed metal salt poplar;

and 4, step 4: drying polyphenol copper-zinc mixed metal salt poplar

Placing the poplar wood with the polyphenol copper-zinc mixed metal salt in a drying kiln to gradually evaporate water in the material, wherein the absolute water content is 12%, and obtaining the poplar complex wood as shown in table 4.

As can be seen from the physical and mechanical properties in table 4, the density, strength, and elastic modulus of the material are increased after the complexing treatment; the dimensional stability is greatly increased; the corrosion resistance, mildew resistance and flame retardant property of the material are greatly improved, and the loss of introduced metal ions (zinc ions and copper ions) is greatly reduced.

TABLE 4 comparison of Populus wood Performance before and after complexation treatment

Performance index	Untreated	Complexing treatment
			Density (g/cm)³)	0.47	0.53
Bending Strength (MPa)	89.2	96.5
			Modulus of elasticity along grain (GPa)	7.7	8.6
Radial dry shrinkage factor (%)	0.18	0.04
			Chord dry shrinkage factor (%)	0.27	0.08
Flame retardant properties	B2	B1
			Mildew resistance	4 stage	Level 1
Corrosion resistance	Grade IV (decay-free)	I grade (Strong corrosion resistant)
			Loss of copper ion	---	12％
Loss of zinc ion	---	11％

Example 5

A method for preparing a complex veneer comprises the following steps:

step 1: preparing a proper amount of veneer

Cutting Quercus acutissima (Albiziavalcataria) wood into 2560cm wood sections, slicing into single boards with the thickness of 0.3mm, and drying to control the water content to be 30%;

step 2: valonea extract guiding-in veneer

Dissolving valonea extract in water, and uniformly stirring to form valonea extract water solution with the concentration of 1.5 g/L;

then soaking the sliced veneer prepared in the step 1 in the valonea extract solution; the dipping time is 120min, the temperature is room temperature, pressurized dipping is adopted, the pressure is 1.2MPa, the dipping amount of the valonea extract is 2.0 percent of the wood mass, the veneer is taken out and placed in a drying kiln, the moisture in the veneer is gradually evaporated, and when the absolute moisture content of the veneer is 30 percent, the veneer is taken out to form a polyphenol veneer;

and step 3: introduction of metal salt into polyphenol single plate

Dissolving ferric sulfate in water, and stirring uniformly to form a ferric sulfate aqueous solution with the concentration of 3.0 g/L;

soaking the polyphenol single plate prepared in the step 2 in the ferric sulfate solution prepared in the step 3 for 90min at room temperature, adopting pressure soaking at the pressure of 1.2MPa to ensure that the soaking amount of ferric sulfate is 1.2% of the mass of the single plate, and taking out the single plate to obtain the polyphenol ferric sulfate salt single plate;

and 4, step 4: drying polyphenol ferric sulfate salt veneer

Placing the polyphenol ferric sulfate salt single plate in the air to gradually evaporate the water in the single plate, wherein the absolute water content is 12%, and obtaining the complex single plate, as shown in figure 6, and the contact angle is shown in figure 7.

As can be seen from FIG. 6, the color of the quercus acutissima veneer is changed into dark gray after complexing treatment, and the texture is more layered; as can be seen from fig. 7, the contact angle of the surface of the treated quercus acutissima veneer is increased compared with that of the untreated quercus acutissima veneer, which shows that the complexing treatment increases the hydrophobic property of the quercus acutissima veneer, and the treated quercus acutissima veneer has no cracks on the surface and good stability.

In conclusion, the invention introduces plant polyphenol, fixes the plant polyphenol in the wood, supports cellulose and/or hemicellulose, and ensures that the plant polyphenol does not cause expansion and drying shrinkage in the processes of moisture absorption and desorption, so that the wood has better stability, and simultaneously has the functions of improving mildew resistance, corrosion resistance and the like of the material.

The foregoing is a preferred embodiment of the present invention, and it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and are intended to be within the scope of the invention.

Claims

1. A method for preparing complex wood, which is characterized by comprising the following steps:

step 1: preparing a proper amount of wood;

step 2: introducing plant polyphenols into wood: soaking the wood in plant polyphenol water solution to lead plant polyphenol into cell cavities, cell walls or cell gaps to obtain polyphenol wood; the concentration of the plant polyphenol water solution is 1 g/L-250 g/L, the average molecular weight is 170-50000, and the plant polyphenol water solution is 1-40 polymers;

and step 3: introducing metal salts into polyphenol wood: soaking the polyphenol wood in a metal salt aqueous solution to lead metal ions into cell cavities, cell walls or intercellular spaces to obtain polyphenol metal salt wood; the concentration of the metal salt water solution is 0.3 g/L-300 g/L; the metal salt is one or more of ferric salt, copper salt, aluminum salt, titanium salt, calcium salt, molybdenum salt, tungsten salt, chromium salt, magnesium salt, potassium salt and double salt thereof;

2. The method according to claim 1, wherein the plant polyphenol is introduced into wood cells, and is bonded to cellulose and hemicellulose in the wood through hydrogen bonding, and the metal salt is bonded to the plant polyphenol through a complexation reaction.

3. The method for preparing complexed wood according to claim 1, wherein the step 2 is:

22) soaking the wood in plant polyphenol water solution;

23) drying the wood impregnated with the aqueous solution of plant polyphenol.

4. The method according to claim 3, wherein the wood is impregnated in the plant polyphenol aqueous solution for 10min to 48h at a temperature of 0 to 80 ℃ under normal pressure or under vacuum and then under pressure.

5. The method of claim 4, wherein the plant polyphenol is one or more of tannin extract, tannin, tannic acid, gallic acid, pyrogallic acid.

6. The method for preparing complexed wood according to claim 1, wherein the step 3 is:

31) dissolving metal salt in water, and stirring uniformly to form a metal salt water solution;

32) immersing the polyphenol wood in a metal salt aqueous solution.

7. The method of claim 6, wherein the wood is immersed in the aqueous solution of metal salt at 0-80 ℃ for 10min-180 days, and the impregnation is performed under normal pressure, under pressure, or under vacuum and then under pressure.

8. The method of claim 6 wherein the aqueous solution of metal salt has a pH of 3.5 to 4.5.

9. The method according to claim 1, wherein in the step 4, the absolute moisture content of the dried polyphenol metal salt wood is 25 to 50%, and then the oxygen content in the air is adjusted to 22 to 50% until the absolute moisture content of the polyphenol metal salt wood is 6 to 12%.