CN115556205B

CN115556205B - Lignin-based wood reinforced preservative, preparation method and application thereof

Info

Publication number: CN115556205B
Application number: CN202211293933.5A
Authority: CN
Inventors: 孙理超; 彭雨馨; 刘涛; 刘珍珍; 王清文; 欧荣贤; 郝笑龙
Original assignee: South China Agricultural University
Current assignee: South China Agricultural University
Priority date: 2022-10-21
Filing date: 2022-10-21
Publication date: 2023-08-29
Anticipated expiration: 2042-10-21
Also published as: CN115556205A

Abstract

The invention discloses a lignin-based wood reinforced preservative, a preparation method and application thereof, and relates to the technical field of wood protection. The lignin-based wood enhancement preservative comprises an A component and a B component; the A component comprises lignin, DMDHEU resin and water in parts by weight; the component B comprises a catalyst and water. The lignin-based wood reinforced preservative provided by the invention has a double preservative system and is excellent in preservative effect on wood. Hydroxyl on DMDHEU resin and hydroxyl on wood undergo a crosslinking reaction, and after curing, cell wall pores can be blocked, so that the activity space of enzymes is effectively reduced, growth substances required by mould and putrescence bacteria such as oxygen, moisture and the like are isolated, and simultaneously, the hydroxyl and the lignin undergo crosslinking, thereby reducing the loss of the lignin and further playing a role in efficient corrosion prevention. The lignin is crosslinked with DMDHEU resin, and the cell cavities of the wood are physically filled, so that the anti-corrosion performance is enhanced, and the physical and mechanical properties of the wood are improved.

Description

Lignin-based wood reinforced preservative, preparation method and application thereof

Technical Field

The invention relates to the technical field of wood protection, in particular to a lignin-based wood reinforced preservative, a preparation method and application thereof.

Background

The wood and the wood products are used as high-efficiency and low-cost carbon sealing bodies, and compared with the traditional building materials such as steel, glass, cement and the like, the energy-saving and carbon-reducing advantages are obvious. The artificial fast-growing wood has the advantages of high yield, high growth speed, short harvesting period and the like, and has been widely paid attention to how to carry out high-value utilization in recent years. However, the loose material and low density of the artificial fast-growing wood cause the artificial fast-growing wood to be extremely easy to mold, decay, blue change and moth, which affects the service life and the comprehensive utilization rate of the artificial fast-growing wood. The wood preservative treatment can improve the performances of the artificial fast-growing wood such as decay resistance, worm damage resistance and the like, but can reduce the physical and mechanical properties of the wood to a certain extent.

The most widely used water-borne preservative at present, and the copper arsenate CCA (chromated copper arsenate) is the most widely used water-borne preservative in recent years, wherein the active ingredients are oxides or salts of copper, chromium and arsenic. However, arsenic and chromium contained in CCA may be harmful to human health and environmental quality, and the waste treatment of CCA treated materials still lacks an adequate way, so CCA is forbidden in many countries, and new methods for wood preservation are urgently needed. Chinese patent CN111993514a discloses a method for preserving wood, which uses ammonia-soluble quaternary ammonium copper solution as preservative, and improves the corrosion resistance and moisture resistance of wood by immersing the preservative solution for vacuum pretreatment and then carbonizing the wood. However, amine or ammonia is volatile, pollutes the environment and affects human health.

Therefore, the development of the non-toxic and environment-friendly lignin-based wood enhanced preservative has important significance for the technical field of wood protection.

Disclosure of Invention

Based on the above, the invention provides the lignin-based wood reinforced preservative, the preparation method and the application thereof, and the lignin-based wood reinforced preservative has the characteristics of low production cost, simple preparation process, no toxicity and environmental protection, and can simultaneously improve the anti-corrosion effect and the physical and mechanical properties of wood.

In order to achieve the above object, the present invention provides the following solutions:

according to one of the technical schemes, the lignin-based wood enhancement preservative comprises a component A and a component B;

the component A comprises, by mass, 8-23 parts of lignin, 50-65 parts of DMDHEU resin (dimethylol dihydroxy cycloethylene urea resin) and 10-40 parts of water; the component B comprises 1-2 parts of catalyst and 100 parts of water.

Further, the lignin is sulfonate alkali lignin or sulfate lignin, and the average molecular weight is 800-1700.

Further, the solid content of the DMDHEU resin is 40-60%.

The lignin in the invention is a natural phenolic polymer compound formed by a phenylpropane unit through a carbon-carbon bond and an ether bond, has high phenolic content and network forming capability, is a weak biocide and can inhibit fungi by more than 50%.

The active nitrogen methylol on the DMDHEU resin can be crosslinked with hydroxyl on the benzene ring of lignin to form macromolecular impregnated wood, so that the moisture absorption is reduced, and a certain corrosion prevention effect is achieved. Lignin has a certain antibacterial effect and is synergistic with DMDHE resin for antibacterial.

The catalyst in the invention is favorable for the DMDHEU resin to be better fixed in wood and form a good and firm macromolecular crosslinked network with phenolic hydroxyl groups in the wood.

Further, the catalyst is one or more of magnesium chloride, zinc chloride and zinc nitrate.

According to a second technical scheme, the preparation method of the lignin-based wood reinforced preservative comprises the following steps of:

uniformly mixing lignin and water, and then adding DMDHEU resin to uniformly disperse to obtain a component A;

and adding the catalyst into water to dissolve, thus obtaining the component B.

Further, mixing lignin with water, stirring for 15-30 min at 400-800 r/min, and then adding DMDHEU resin for ultrasonic dispersion for 30-60 min to obtain the component A. The preparation process is carried out at room temperature.

In a third technical scheme of the invention, the lignin-based wood enhancement preservative is applied to wood protection.

Further, the wood is fast-growing wood, and specifically is one of poplar, pine or fir.

Further, the wood is immersed in the component A, dried and then immersed in the component B, and cured, so that the wood after the corrosion-resistant treatment is obtained.

Further, the conditions for impregnation in the component A and the component B are as follows: vacuumizing for 0.5-1 h under the vacuum degree of minus 0.09 to minus 0.08, and pressurizing for 1-2 h under the pressure of 0.5-0.6 MPa.

Further, the step of air-drying for 1 day is included after the completion of the impregnation in the A component.

Further, the curing specifically includes: curing at 55-65deg.C for 2-4 hr, and then heating to 115-125deg.C at 20-30deg.C/min for 2-6 hr.

The technical conception of the invention is as follows:

most of the current preservative studies on lignin are still in a theoretical stage and cannot be applied. The invention provides a novel lignin and DMDHEU resin co-modification scheme, which uses biomass resource lignin, and utilizes the advantages of natural antibacterial property, innocuity, harmlessness and low cost of lignin, thereby solving the problem that lignin is easy to run off when entering wood, and enhancing the anti-corrosion performance of DMDHEU resin to the wood. In addition, lignin is taken as a natural skeleton structure of the wood, so that the physical and mechanical properties of the wood can be improved to a certain extent, and the corrosion resistance and physical and mechanical properties of the modified wood are obviously improved.

The invention discloses the following technical effects:

(1) The lignin-based wood reinforced preservative provided by the invention has a double preservative system and is excellent in preservative effect on wood. Hydroxyl on DMDHEU resin and hydroxyl on wood undergo a crosslinking reaction, and after curing, cell wall pores can be blocked, so that the activity space of enzymes is effectively reduced, growth substances required by mould and putrescence bacteria such as oxygen, moisture and the like are isolated, and simultaneously, the hydroxyl and the lignin undergo crosslinking, thereby reducing the loss of the lignin and further playing a role in efficient corrosion prevention. The lignin is crosslinked with DMDHEU resin, and the cell cavities of the wood are physically filled, so that the anti-corrosion performance is enhanced, and the physical and mechanical properties of the wood are improved.

(2) The DMDHEU resin is partially crosslinked with lignin and is fixed in wood, so that the adhesion capability of the lignin is enhanced, the anti-loss performance of the preservative is further enhanced, and the service life of the preservative is prolonged.

(3) The lignin is used as a natural skeleton structure of the wood, so that the physical and mechanical properties of the wood can be improved to a certain extent, a better mechanical supporting effect is achieved on the wood, and the lignin and the wood have better biocompatibility.

(4) The catalyst magnesium chloride helps the DMDHEU resin to fix in the wood.

(5) The preparation method is simple, the reaction conditions such as temperature are not high, and the prepared preservative is nontoxic and harmless and has low cost. The lignin-based reinforced preservative prepared by the method has moderate viscosity, and can be well solidified in the wood in the vacuum high-pressure impregnation process to form a strong and compact crosslinked structure. The fast-growing wood treated by the lignin-based enhanced preservative has obviously improved physical and mechanical properties and corrosion resistance, and has important significance for high-value utilization of the fast-growing wood.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is an infrared spectrum of poplar samples prepared in example 3 and comparative example 1 of the present invention;

FIG. 2 is a graph showing the weight gain of poplar samples prepared in examples 1-5 and comparative examples 2-3 according to the present invention;

FIG. 3 shows the expansion coefficients of poplar samples prepared in examples 1 to 5 and comparative examples 2 to 3 according to the present invention;

FIG. 4 shows flexural modulus of poplar samples modified in examples 1-5 and comparative examples 2-3 according to the present invention;

FIG. 5 shows the flexural strength of poplar samples prepared in examples 1-5 and comparative examples 2-3 according to the present invention;

FIG. 6 is a graph showing the hardness test results of poplar samples prepared in examples 1 to 5 and comparative examples 2 to 3 according to the present invention;

FIG. 7 is a graph showing the results of the cis-grain compressive strength test of the poplar samples prepared in examples 1 to 5 and comparative examples 2 to 3 according to the present invention;

FIG. 8 is a graph showing the mass loss of poplar samples prepared in examples 1 to 5 and comparative examples 1 to 3 according to the present invention after 30 days of treatment with white rot fungi;

FIG. 9 is an electron microscopic image of poplar samples prepared in comparative examples 1-2 and example 2 according to the present invention after 30 days of decay experiments with white rot fungi.

Detailed Description

Various exemplary embodiments of the invention will now be described in detail, which should not be considered as limiting the invention, but rather as more detailed descriptions of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the invention described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present invention. The specification and examples of the present invention are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.

The experimental methods used in the examples below were all conventional, unless otherwise specified.

The percentage of the total mass of the composition is "%", unless otherwise specified. However, the percentage of the solution, unless otherwise specified, means that 100mL of the solution contains several grams of solute; the percentage between liquids refers to the ratio of the volumes at 20 ℃.

The room temperature and the normal temperature are 20-30 ℃ unless otherwise specified.

The raw materials used in the examples and comparative examples of the present invention were obtained from the purchase route unless otherwise specified.

The average molecular weight of the alkali sulfonate lignin used in the examples of the present invention and comparative examples is 800 to 1700.

The small wood blocks used in the examples of the present invention and the comparative examples were poplar wood blocks.

Example 1

Step 1, weighing 8.2g of alkali sulfonate lignin at normal temperature and normal pressure, adding 38.3g of deionized water, stirring for 30min at 400r/min at normal temperature, then adding 55.7g of DMDHEU resin with the solid content of 55%, enabling the concentration of the DMDHEU resin to be 30%, and performing ultrasonic dispersion on the solution for 30min to obtain the component A. 1.5g of magnesium chloride solid is weighed at normal temperature and pressure, and 100g of deionized water is added for dissolution, so that a component B is prepared.

And 2, fully immersing the wood block into the component A, vacuumizing for 30min at the vacuum degree of-0.08, and then pressurizing for 1h at the pressure of 0.5 MPa. Air-drying at room temperature for 1 day, immersing the wood block into the component B, vacuumizing for 30min under-0.08 vacuum degree, and pressurizing for 1h under 0.5 MPa. Finally, curing for 2 hours at 60 ℃ in an electric blast drying oven, and then heating to 120 ℃ at the speed of 25 ℃/min, and curing for 2 hours to obtain the reinforced anti-corrosion treatment wood.

Example 2

Step 1, weighing 12.3g of alkali sulfonate lignin at normal temperature and normal pressure, adding 34.2g of deionized water, stirring for 30min at 400r/min at normal temperature, then adding 55.7g of DMDHEU resin with the solid content of 55%, enabling the concentration of the DMDHEU resin to be 30%, and carrying out ultrasonic dispersion on the solution for 30min to obtain the component A. 1.5g of magnesium chloride solid is weighed at normal temperature and pressure, and 100g of deionized water is added for dissolution, so that a component B is prepared.

And 2, fully immersing the wood block into the component A, vacuumizing for 30min at the vacuum degree of-0.08, and then pressurizing for 2h at the pressure of 0.5 MPa. Air-dried at room temperature for 1 day. The wood block was then immersed in the B component, evacuated for 30min at-0.08 vacuum, and then pressurized at 0.5MPa for 1h. Finally, curing for 2 hours at 60 ℃ in an electric blast drying oven, and then heating to 120 ℃ at the speed of 25 ℃/min, and curing for 2 hours to obtain the reinforced anti-corrosion treatment wood.

Example 3

And step 1, weighing 16.3g of alkali sulfonate lignin at normal temperature and normal pressure, adding 30.1g of deionized water, stirring for 30min at normal temperature and 500r/min, then adding 55.7g of DMDHEU resin with the solid content of 55%, enabling the concentration of the DMDHEU resin to be 30%, and performing ultrasonic dispersion on the solution for 30min to obtain the component A. 1.5g of magnesium chloride solid is weighed at normal temperature and pressure, and 100g of deionized water is added for dissolution, so that a component B is prepared.

And 2, fully immersing the small wood blocks into the component A, vacuumizing for 30min at the vacuum degree of-0.08, and then pressurizing for 2h at the pressure of 0.5 MPa. Air-dried at room temperature for 1 day. The small wood pieces were then immersed in the B-component, evacuated for 30min at-0.08 vacuum, and then pressurized at 0.5MPa for 1h. Finally, curing for 2 hours at 60 ℃ in an electric blast drying oven, and then heating to 120 ℃ at the speed of 25 ℃/min, and curing for 2 hours to obtain the preservative treated wood.

Example 4

Step 1, weighing 22.5g of alkali sulfonate lignin at normal temperature and normal pressure, adding 95.9g of deionized water, stirring for 30min at normal temperature and 600r/min, and then adding 62.5g of DMDHEU resin with the solid content of 55% to ensure that the concentration of the DMDHEU resin is 20%. The solution was ultrasonically dispersed for 30 minutes to prepare the a-component. 1.5g of magnesium chloride solid is weighed at normal temperature and pressure, and 100g of deionized water is added for dissolution, so that a component B is prepared.

And 2, fully immersing the small wood blocks into the component A, vacuumizing for 30min at the vacuum degree of-0.08, and then pressurizing for 1h at the pressure of 0.5 MPa. Air-dried at room temperature for 1 day. The small wood pieces were then immersed in the B-component, evacuated for 30min at-0.08 vacuum, and then pressurized at 0.5MPa for 1h. Finally, curing for 2 hours at 60 ℃ in an electric blast drying oven, and then heating to 120 ℃ at the speed of 25 ℃/min, and curing for 2 hours to obtain the preservative treated wood.

Example 5

Step 1, weighing 9g of alkali sulfonate lignin at normal temperature and normal pressure, adding 11.5g of deionized water, stirring for 60min at normal temperature and 400r/min, and then adding 55.7g of DMDHEU resin with the solid content of 55%, so that the concentration of the DMDHEU resin is 40%. The solution was ultrasonically dispersed for 60 minutes to prepare the A component. 1.5g of magnesium chloride solid is weighed at normal temperature and pressure, and 100g of deionized water is added for dissolution, so that a component B is prepared.

And 2, fully immersing the small wood blocks into the component A, vacuumizing for 30min at the vacuum degree of-0.08, and then pressurizing for 2h at the pressure of 0.5 MPa. Air-drying at room temperature for 1 day, immersing the small wood block into the component B, vacuumizing for 30min under-0.08 vacuum degree, and pressurizing for 1h under 0.5 MPa. Finally, curing for 2 hours at 60 ℃ in an electric blast drying oven, and then heating to 120 ℃ at the speed of 25 ℃/min, and curing for 2 hours to obtain the preservative treated wood.

Comparative example 1

Drying the wood at the temperature of 103 (+ -2) DEG C until the wood is absolute dry, and preparing physical mechanical test pieces with various sizes.

Comparative example 2

Step 1, weighing 9.5g of alkali sulfonate lignin at normal temperature and normal pressure, adding 70g of deionized water, and stirring for 60min at normal temperature and 500r/min to obtain a component A. 1.5g of magnesium chloride solid was weighed at normal temperature and pressure, and 100g of deionized water was added to prepare a component B.

And 2, fully immersing the small wood blocks into the component A, vacuumizing for 30min at the vacuum degree of-0.08, and then pressurizing for 2h at the pressure of 0.5 MPa. Air-dried at room temperature for 1 day. The small wood pieces were then immersed in the B-component, evacuated for 30min at-0.08 vacuum, and then pressurized at 0.5MPa for 1h. Finally, curing for 2 hours at 60 ℃ in an electric blast drying oven, then heating to 120 ℃ at the speed of 25 ℃/min, and curing for 2 hours to obtain the anti-corrosion mildew-proof agent treated wood.

Comparative example 3

Step 1, 55.7g of DMDHEU resin with the solid content of 55% is weighed at normal temperature and normal pressure, and 46.4g of deionized water is added. The component A is prepared. 1.5g of magnesium chloride solid was weighed at normal temperature and pressure, and 100g of deionized water was added to prepare a catalyst magnesium chloride.

And 2, fully immersing the small wood blocks into the component A, vacuumizing for 30min at the vacuum degree of-0.08, and then pressurizing for 2h at the pressure of 0.5 MPa. Air-drying at room temperature for 1 day, immersing the small wood block into the component B, vacuumizing for 30min under-0.08 vacuum degree, and pressurizing for 1h under 0.5 MPa. Finally, curing for 2 hours at 60 ℃ in an electric blast drying oven, then heating to 120 ℃ at the speed of 25 ℃/min, and curing for 2 hours to obtain the anti-corrosion mildew-proof agent treated wood.

Comparative example 4

The only difference from example 2 is that the DMDHEU resin is replaced with an epoxy resin (EP).

Results: compared with example 2, the anti-corrosion and mildew-proof agent prepared in the comparative example has poorer anti-corrosion performance of wood, and the physical and mechanical properties of wood are poorer than those of the wood treated by the anti-corrosion and mildew-proof agent prepared in example 2.

Examples 1-5 finally produced a poplar block modified with both DMDHEU resin and lignin, comparative example 1 was a blank comparative example, an unmodified poplar block was obtained, comparative example 2 was a lignin-modified-only poplar block, and comparative example 3 was a DMDHEU resin-only poplar block.

The following tests were performed on the poplar wood pieces prepared in examples 1 to 5 and comparative examples 1 to 3:

fourier infrared (FTIR) determination: perkinElmer Spectrum100FTIR spectrometer and Nicoletnexus470 FTIR spectrometer using potassium bromide tabletting technique at 4000-500cm ^-1 In-range scanning, resolution is4cm ^-1 FTIR spectra of comparative example 1 and example 2 were tested.

Weight gain rate measurement: the experiments used poplar blocks of 20mm (L) by 20mm (T) by 20mm (R) size, with 10 replicates per group. The sample is first dried to absolute dryness and its mass m is recorded ₀ . And then placing the sample into an immersion vacuum tank for vacuum pressurization until the sample repeatedly absorbs the immersion liquid, then air-drying for 24 hours, and then placing the sample into a blast drying box for heating and curing, wherein the curing condition is that the sample is cured for 2 hours at 60 ℃ firstly, and then the temperature is raised to 103 ℃ for curing for 12 hours. Taking out the solidified test piece, placing the test piece in a dryer for about 1h, and cooling to room temperature to measure the absolute dry mass m of the immersed material ₁ . Weight gain rate of 100% (m) ₁ -m ₀ )/m ₀ And an average value is calculated.

Determination of the coefficient of expansion: the expansion coefficient resistance measurement experiment is carried out by using unmodified and modified poplar samples with the diameter of 20mm (L) by 20mm (T) by 20mm (R), and 10 parallel samples are used in each group. The chord and radial dimensions of all samples after absolute drying are measured, then water is soaked for 10 days, water is changed every 48 hours during the period, and the chord and radial dimensions of the water saturation state of the test samples after soaking for 10 days are recorded. The coefficient of expansion resistance is (S _u -S _t )/S _u *100, wherein S _u Is the average wet expansion rate of untreated material, S _t Is the average wet expansion rate of the treatment material.

Flexural Strength, flexural modulus measurement: the experiment selects unmodified and modified poplar samples with the length of 180mm (L) and the length of 10mm (T) and the length of 10mm (R), 15 parallel samples are adopted in each group, a model CMT-1000 universal mechanical testing machine is adopted for three-point bending test, wherein the span is 150mm, the loading speed is 6mm/min, the bending modulus and the bending strength are measured, and the average value is obtained.

Hardness measurement: unmodified and modified poplar samples of 50mm (L) by 50mm (T) by 20mm (R) were used in the experiment, 15 samples were used in each group, and the hardness of the samples was measured according to GB/T1941-2009 and the average value was obtained.

Compressive strength along grain: unmodified and modified poplar samples of 50mm (L) by 50mm (T) by 20mm (R) are selected for the experiment, 15 samples are used in each group of parallel samples, the grain compressive strength of the samples is measured according to GB/T1939-2009, and the average value is obtained.

And (3) corrosion resistance test: the experiment selects unmodified poplar samples and modified poplar samples with the length of 20mm (L) and the length of 20mm (T) and the length of 10mm (R), each group of parallel samples is 36, and the absolute dry mass m of the immersed samples to be measured is measured ₃ And sterilized at high temperature (121 ℃ C. For 30 minutes). The sample was then placed under aseptic conditions in a petri dish filled with white rot fungus mycelia. Culturing at 25deg.C for 12 weeks under 65% humidity, scraping mycelium on the surface of sample, sterilizing at high temperature, and oven drying to obtain white rot fungus rot sample mass m ₄ . The mass loss rate was 100 x (m ₃ -m ₄ )/m ₃ 。

The test results were as follows:

FIG. 1 is an infrared spectrum of poplar samples prepared in example 3 and comparative example 1 of the present invention, showing that modification is effective from the change of infrared characteristic peaks. EXAMPLE 3 carbonyl at 1737cm ^-1 Offset to 1708cm ^-1 The position and vibration are enhanced because the structure of the DMDHEU resin molecule is offset by O=C-N bond after the DMDHEU resin molecule is introduced into the system. The characteristic absorption peak of the C-O-C bond is 1049cm ^-1 Offset to 1034cm ^-1 The surface wood can be crosslinked with the DMDHEU resin and the DMDHEU resin can form ether bonds through self-condensation reaction. Example 3 at 772 and 818cm- ¹ Alcohol-specific methylene groups occur, which are formed by crosslinking lignin with DMDHEU resin or with wood.

FIG. 2 shows the weight gain of the poplar samples modified in examples 1 to 5 and comparative examples 2 to 3 according to the present invention (the "example" in the figure means "example"). The weight gain rate of comparative example 2 was 20.4%, while the weight gain rate of comparative example 3 reached 46.3%. This is because the alkaline lignin used in this study has a relatively large molecular weight and a non-uniform molecular weight distribution (Mn: 1595, PD: 1.03), only a portion of the small molecular lignin can enter wood cells, and lignin is relatively difficult to fix in the wood cell cavities. Unlike lignin, DMDHEU resin has a molecular weight of only 178, can diffuse into the interior of wood relatively easily under external pressure, deposit in the cell cavities and cell gaps of wood, and even part of the resin can enter the cell walls of wood to react with hydroxyl groups on the cell walls of wood to crosslink. As the lignin concentration increases, the rate of weight gain of examples 1 and 2 also increases, meaning that the addition of DMDHEU resin helps to fix lignin in the wood and reduce lignin loss in the wood. The weight gain of the modified wood in example 2 reached a maximum of 42.5%. However, as the lignin concentration increases, the rate of weight gain of example 3 decreases. Presumably, the higher lignin concentration in the impregnation solution resulted in an increase in viscosity, which made penetration into the wood cells difficult; meanwhile, the high concentration of the impregnating solution is easy to pre-polymerize, so that the products with large molecular weight are more difficult to enter wood cells, and the weight increasing effect is weakened.

FIG. 3 shows the expansion coefficients of the poplar samples modified in examples 1 to 5 and comparative examples 2 to 3 according to the present invention (the "example" in the figure means "example"). The ASE of both comparative examples 2-3 and examples was greater than 0, indicating that both lignin and DMDHEU resin impregnation treatments had a positive effect on the dimensional stability of wood, resulting in a treated wood with better water resistance. After wood is treated by lignin, part of lignin can enter into the wood cell cavities to physically fill the wood cell cavities, so that the absorption of external moisture can be reduced, and the dimensional stability of the wood is improved. The DMDHEU resin with small molecular weight can well fill pores of wood cell walls, permanent cell wall expansion is generated, accessibility of water molecules to adsorption sites is reduced, and therefore stability of wood size is improved to a greater extent. The ASE of examples 2 and 5 was effective in the composite impregnation modification, and it was revealed that a part of lignin was crosslinked with DMDHEU resin to form a network and fixed in wood, and the degree of swelling of wood was increased, blocking the water passage of wood. And the DMDHEU resin with high concentration is beneficial to enhancing the water resistance of the modified material.

FIGS. 4 to 5 show flexural modulus (FIG. 4) and flexural strength (FIG. 5) of poplar samples modified in examples 1 to 5 and comparative examples 2 to 3 according to the present invention, and "examples" in the figures represent "examples". The flexural modulus of the treatment material of comparative example 3 increased from 5.5GPa to 7.1GPa, and the flexural modulus of examples 1 to 5 showed a gradual increase trend with increasing lignin concentration, with MOE increasing to 8.3GPa,8.9GPa,8.6GPa,8.2GPa,9GPa, respectively. Because lignin is physically filled in the cell cavities of the wood, the lignin plays roles of dispersing and transferring stress to wood cells, so that the DMDHEU resin is deformed under the action of external force to reduce the filling of pores of the cell walls of the wood, has a certain supporting effect on the pores of the cell walls, and increases the resistance to external load, thereby enhancing the capability of the wood for resisting external deformation. The flexural strength of examples 1-5 also showed a substantially rising trend, with the flexural strength of comparative example 2 increased to 72MPa and the MOR of comparative example 3 increased to 80.1MPa. After lignin is modified by compounding DMDHEU resin, the bending strength of the wood reaches 90MPa at maximum. This is because as the lignin concentration increases, more lignin molecules may crosslink with the resin to form a network polymer, which is deposited in the cell cavity to form a rigid reinforcement, resulting in an increase in the rate of weight gain of the modified wood and an increase in bending strength. In addition, the hydroxyl reaction of the DMDHEU resin and the wood cell wall and the self-condensation reaction of the DMDHEU resin increase the rigidity of the cell wall, so that the bending strength and the bending modulus of the wood are improved.

FIGS. 6-7 are results of the test of the grain compressive strength (FIG. 7) and hardness (FIG. 6) of the poplar samples modified in examples 1-5 and comparative examples 2-3 according to the present invention, and "example" in the figure indicates "example". As can be seen from fig. 6-7, after lignin/DMDHEU resin impregnation modification, the hardness of poplar fast-growing wood increased from 2339N to 3190N (example 1), 3742N (example 2), 3660N (example 3), 3210N (example 4) and 3850N (example 5), respectively, by 36%,60%,56%,37% and 64%. The compressive strength of the following grain in comparative example 1 was 56.3MPa, and the compressive strength of the following grain gradually increased with the increase of lignin concentration, and in example 5, the compressive strength of the following grain reached a maximum of 113MPa, which was improved by 90% compared with untreated material. The reason why the compressive strength of the wood after the modification is remarkably increased is that the chemical modifier is impregnated into the conduits of the wood and the cells cavities, the micropores of the walls and the gaps between the cells of the wood. The modifier is deposited in a large amount in the porous structure of wood cells after solidification, and when the modifier is stressed, the deformation of the gaps of the wood cells becomes small, so that the relative degree of freedom of the microfiber filaments is reduced, and finally the compressive strength of the wood is increased.

FIG. 8 is a graph showing the mass loss after 30 days of treatment with white rot fungi of examples 1 to 5 and comparative examples 1 to 3 of the present invention, wherein "example" in the graph indicates "example". According to GB/T1349.2, calculating the mass loss rate, wherein the mass loss rate of comparative example 1 after white rot fungi decay is 58%, and the mass loss rate belongs to a non-corrosion-resistant grade (more than or equal to 45%); the mass loss rate of comparative example 2 impregnated with lignin alone was 23, belonging to the corrosion resistant class (11-24%); the mass loss rate of comparative example 3 was 15.5%, which was corrosion resistant grade (11 to 24%). The mass loss rate of the compound modified treatment material is 13 percent (example 1), 8.5 percent (example 2), 18 percent (example 3), 10 percent (example 4) and 12 percent (example 5) respectively, and the compound modified treatment material belongs to corrosion resistance grade and above. The results show that the poplar wood has no anti-corrosion effect on white rot fungi, and the anti-bacterial effect is obviously improved after the DMDHEU resin and lignin are compounded and modified, so that the anti-corrosion grade and above can be achieved, wherein the effect of the embodiment 2 is better.

FIG. 9 is an electron microscopic image of the poplar samples prepared in comparative examples 1-2 and example 2 after 30 days of decay experiments with white rot fungi. A large number of distinct hyphae were observed in the electron microscopy image of comparative example 1, and some wood matrix was destroyed. The electron microscopic image of comparative example 2 showed that a small number of mycelia remained on the cell wall, and the wood matrix was slightly destroyed, indicating better corrosion resistance than the untreated wood of comparative example 1. The number of hyphae found on the cell wall in the wood of example 2 was the least, and the mass loss of the modified wood of example 2 was 8.5% in combination, indicating that the modified wood of example 2 had higher corrosion resistance than comparative examples 1 and 2. The electron microscopy results are consistent with the mass loss rate results, which further proves that the DMDHEU resin and lignin have good antibacterial property on white rot fungi.

The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.

Claims

1. The use of a lignin-based wood enhancement preservative in wood protection, characterized in that the lignin-based wood enhancement preservative consists of a component a and a component B;

the A component consists of 8-23 parts of lignin, 50-65 parts of DMDHEU resin with the solid content of 40-60% and 10-40 parts of water in parts by mass; the component B consists of 1-2 parts of a catalyst and 100 parts of water;

firstly, soaking wood in the component A, drying, then soaking in the component B, and curing to obtain the wood after the corrosion-resistant treatment;

the curing is specifically as follows: curing at 55-65deg.C for 2-4 hr, and then heating to 115-125deg.C at 20-30deg.C/min for 2-6 hr;

the lignin is sulfonate alkaline lignin or sulfate lignin, and the average molecular weight is 800-1700.

2. The use according to claim 1, wherein the catalyst is one or more of magnesium chloride, zinc chloride and zinc nitrate.

3. The use according to claim 1, characterized in that the method for preparing lignin-based wood-reinforcing preservative comprises the steps of:

and adding the catalyst into water to dissolve, thus obtaining the component B.

4. The use according to claim 1, wherein the conditions of impregnation in both the a-and B-components are: vacuumizing for 0.5-1 h under the vacuum degree of-0.09 to-0.08, and pressurizing for 1-2 h under the pressure of 0.5-0.6 MPa.

5. The use according to claim 1, further comprising the step of air-drying for 1 day after the completion of the impregnation in the a-component.