A reinforcing agent and a reinforcing method for water-saturated wooden cultural relics using the reinforcing agent

Abstract

The present invention relates to a reinforcing agent and a method for reinforcing water-saturated wooden cultural relics using the reinforcing agent, belonging to the technical field of wooden cultural relic reinforcement and protection. The reinforcing agent is made from raw materials consisting of 5 parts of PVAc, 40-60 parts of methanol, 1-10 parts of shellac, and 1-7 parts of H2O2. The reinforcing agent prepared by the present invention has good permeability, a simple preparation process, maintains good biocompatibility with water-saturated wooden cultural relics, effectively improves the strength, toughness, and stability of reinforced water-saturated wooden cultural relics, and meets the requirements for color quality changes after reinforcement of water-saturated wooden cultural relics.

Description

Technical Field

[0001] The invention relates to a reinforcing agent and a method for reinforcing water-saturated wooden cultural relics by using the reinforcing agent, belonging to the technical field of reinforcing and protecting wooden cultural relics. Background Art

[0002] my country is a vast country with significant climate differences between the north and south. Archaeologically, wooden artifacts unearthed in different regions often experience varying degrees of decay. While research on the preservation of wooden artifacts in arid regions has been extensive both domestically and internationally, the preservation of wooden artifacts in humid environments (water-saturated wooden artifacts) is a more targeted and complex task. Influenced by numerous factors, including the regional environment (temperature, humidity, microbial growth, etc.) and the structural characteristics of the site, it has been less thoroughly studied and the technology is less mature. Water-saturated wooden artifacts are typically found in areas with high relative humidity and soil moisture. This results in high internal moisture content in unearthed wooden artifacts, which can be severely damaged by microbial corrosion, resulting in severe damage to the internal fiber structure. For example, the coffin wood excavated from the Tomb of Marquis Yi of Zeng had a maximum water saturation of 400%, with a moisture content ranging from 4% to 80%. Due to the fragility of wooden artifacts, conventional reinforcement methods commonly used in conventional environments often suffer from a range of issues, including difficulty in curing, overly rapid curing, bleaching, blackening, or reflective discoloration of the cured material, poor permeability, and poor compatibility of the reinforcement agent with organic artifacts. These methods also place stringent requirements on reinforcement materials, preservation environments, and construction techniques.

[0003] The current method for reinforcing water-saturated wooden cultural relics using PVAc solutions often involves modifying the PVAc. While this modification improves the performance of the PVAc, the increase in reinforcement strength is minimal compared to the requirements of cultural relic preservation, and the desired effect falls short. For example, Yin Xiaoxiang et al. added a polyallylamine solution, which reacts with carbon dioxide in the air to form a three-dimensional gel network structure, to a PVAc emulsion to increase the system's toughness and stability. However, the preparation process is complex and time-consuming. Kang Yuying et al. synthesized a silicone-modified PVAc emulsion via free radical polymerization, but the improvement in hydrophobicity was modest, as the reaction is influenced by numerous factors and the degree of polymerization is difficult to control.

[0004] Sun Peiqin and others used PVAc to coat hemp fibers, reducing the water absorption rate of hemp fibers to 5%. In-situ polymerization used small molecule monomers for polymerization reinforcement, which has good permeability. However, it is a free radical polymerization reaction, which will release heat strongly and damage water-saturated wooden cultural relics. At the same time, the composition of water-saturated wooden cultural relics is complex, containing more water and impurities, which will cause some side reactions, increase the induction period of the polymerization reaction, and cause many interfering factors in the reinforcement process. Therefore, considering the permeability factor, it is not easy to use in-situ polymerization reinforcement method in wooden cultural relics. Summary of the Invention

[0005] The purpose of the present invention is to provide a reinforcing agent that can maintain good biocompatibility with water-saturated wooden cultural relics, effectively improve the strength, toughness and stability of water-saturated wooden cultural relics after reinforcement; and meet the requirements for color quality change of water-saturated wooden cultural relics after reinforcement, and a method for reinforcing water-saturated wooden cultural relics using the reinforcing agent.

[0006] The technical solution of the present invention is

[0007] A reinforcing agent, which is made from the following raw materials in parts by mass:

[0008] 5 parts of PVAc

[0009] 40-60 parts of methanol

[0010] 1-10 parts shellac

[0011] 1~7 parts H2O2

[0012] The preparation method of the reinforcing agent is:

[0013] According to the above ratio, methanol is first placed in a container, shellac is added, and H2O2 is added dropwise. After standing for 5 to 10 minutes, it is slowly stirred to mix the methanol, shellac and H2O2 in the container evenly to form a mixed solution. During the stirring process, the mixed solution in the container gradually changes from colorless to light brown, and PVAc is added and stirred to completely dissolve it. The resulting low-viscosity brown colloidal solution is the reinforcing agent.

[0014] The mass concentration of the H2O2 is 30%.

[0015] The method for reinforcing water-saturated wooden cultural relics using the reinforcing agent comprises the following steps:

[0016] 1) First, the degree of decay of wooden cultural relics is evaluated as high, medium, low, or weak based on the water saturation rate;

[0017] 2) Prepare different proportions of reinforcing agents based on the degree of decay of wooden cultural relics of different grades. At the same time, since wooden cultural relics have been buried underground for a long time, their surface color will inevitably become darker and blacker. They need to be bleached by spraying a small amount of 2-5% oxalic acid solution multiple times, with an interval of 2 hours between each bleaching, until the surface color of the wooden cultural relics becomes lighter.

[0018] 3) After the decolorization treatment is completed, spray anhydrous methanol evenly on the surface of the wooden cultural relics to clean the oxalic acid solution remaining on the surface of the wooden cultural relics. The number of methanol sprays is 2-3 times, with an interval of 1 hour each time.

[0019] 4) After the reinforcement agent is prepared, evenly drip or spray it on the surface of the wooden cultural relics until the reinforcement agent is completely penetrated and there are no droplets hanging on the surface of the wooden cultural relics. Then dry it in a low humidity environment of 25℃ for 8-9 hours; the reinforcement of the wooden cultural relics is completed.

[0020] In the evaluation of the grades of high, medium, low and weak in step 1), a water saturation rate of 300-400% or above is defined as highly decayed; a water saturation rate of 200-300% is defined as moderately decayed; a water saturation rate of 100-200% is defined as lowly decayed; and a water saturation rate of less than 100% is defined as weakly decayed.

[0021] In order to demonstrate the performance of the reinforcing agent, the inventors tested the mass and density increase rate, as well as the compressive strength of dense and loose samples before and after reinforcement.

[0022] Density increase rate

[0023] Experimental objects: The dense blank and reinforced samples, and the loose blank and reinforced samples were selected from the coffin wood samples unearthed from the Zenghouyi Tomb.

[0024] Experimental method: First, weigh and record the mass m1 of the wooden cultural relic before reinforcement, and then weigh and record the mass m2 of the wooden cultural relic after reinforcement.

[0025] Since wooden cultural relics have a certain degree of water absorption, there will be a large error in measuring their volume directly by the drainage method. The volume (v) remains unchanged before and after reinforcement. The density (ρ) = mass (m) ÷ volume (v), so the mass increase rate of wooden cultural relics is also the density increase rate, ρ1 = m1 ÷ v, ρ2 = m2 ÷ v, and the density increase rate = (ρ2-ρ1) / ρ1×100%= (m2-m1) / m1×100%.

[0026] Experimental results: Calculations show that the density increase before and after reinforcement varies among wooden artifacts of varying degrees of decay. Dense specimens, with smaller surface areas and smaller porosities, saw a 2.3% increase in density before and after reinforcement. Loose specimens, with larger surface areas and greater porosity, saw a 33.3% increase in density before and after reinforcement. Overall, the density of the reinforcement agent is relatively low, and the weight of the wooden artifacts after reinforcement does not change significantly.

[0027] Wood parallel grain compressive strength test

[0028] Experimental objects: Dense blank and reinforced specimens, loose blank and reinforced specimens were selected from the coffin wood samples unearthed from the Zenghouyi Tomb.

[0029] Test method: The test was conducted in accordance with the National Standard of the People’s Republic of China GB 1935-1991 Test method for compressive strength of wood parallel to the grain.

[0030] Experimental results: The compressive strength of dense specimens increased by 47.0% before and after reinforcement; the compressive strength of loose specimens increased by 115.4% before and after reinforcement. The average compressive strength increased by 81.2%. This indicates that dense specimens are harder and inherently have better compressive strength, making it difficult for the reinforcement to penetrate, resulting in no significant increase in compressive strength before and after reinforcement. Loose specimens are honeycomb-shaped, softer, inherently have poor compressive strength, are severely decayed, have many large pores, and a large specific surface area. The reinforcement covers more of the surface, making it easier to penetrate, and the compressive strength increases significantly (see Appendix). Figure 1 、 2 ). Specific test results are shown in the table below:

[0031] Table 1 Mass and density increase rate (mass increase rate) of dense and loose specimens before and after reinforcement

[0032]

[0033] Table 2 Compressive strength test of dense and loose samples along the grain

[0034]

[0035] Scanning electron microscope test

[0036] Experimental Subjects: Dense blank and reinforced specimens, as well as loose blank and reinforced specimens, were selected from coffin wood samples unearthed from the Zenghouyi Tomb. Experimental Methods: Surface and cross-sectional microstructures of the wooden artifacts before and after reinforcement were observed using a field emission scanning electron microscope (SU 8010).

[0037] Experimental results: Before reinforcement, the dense wood sample had a powdered surface, with numerous pits of varying depths, powdered wood particles, and impurities. After reinforcement, the pore structure was largely filled with the reinforcement agent. Furthermore, despite the high concentration and relatively large amount of hydrogen peroxide added, the colloid did not precipitate. After curing, no insoluble matter remained or was produced, and the wood surface roughness was reduced, demonstrating that the formulation of the experimental materials used in this study was optimal. The powdered wood particles and thin wood chips were encapsulated by the reinforcement agent, bonding them to the wood and preventing them from falling off, effectively protecting and reinforcing the wooden artifact. Before reinforcement, the loose sample was particularly infested with insects. Furthermore, due to the humid burial environment, it had numerous pores and contained numerous impurities, resulting in a softened and brittle texture. After reinforcement, however, the reinforcement agent penetrated well into the wood through the pores, forming a transparent PVAc film covering the wood's surface structure, insulating the wood from harmful external factors such as oxygen and moisture. The density and viscosity of the added reinforcement are not high, and the relatively large groove pore structure in the wood is not completely filled due to gravity, making the wood surface completely flat and smooth. Otherwise, obvious white adhesive residue will appear on the surface, making it white, reflective, and poorly breathable, affecting the appearance of the cultural relics. This is also the advantage of the optimal formula of this experiment compared to the traditional epoxy resin with high viscosity and slow curing (see Appendix Figure 3 ).

[0038] Fourier transform infrared spectroscopy (FT-IR) test (see attached Figure 4 、 5 )

[0039] Experimental Subjects: Dense, unreinforced, and loose, unreinforced samples from the coffin wood excavated from the Zenghouyi Tomb were used. Experimental Methods: A Nicolet IS 50 FT-IR was used in a dry environment at 25°C to examine the molecular structural characteristics of the surface texture of both dense and loose samples before and after reinforcement. The instrument was preheated and the wood samples ground. Solid samples were then prepared using the pelleting method. Finally, infrared spectroscopy was performed and the results analyzed.

[0040] Experimental results: Figure 4 In the figure, (1) is the infrared spectrum of the dense blank sample before reinforcement, (2) is the infrared spectrum of the loose blank sample; (3) is the infrared spectrum of the dense reinforced sample after reinforcement; and (4) is the infrared spectrum of the loose reinforced sample after reinforcement.

[0041] 3422.78 cm -1 Corresponding to hydroxyl group -OH, 2938.24 cm -1 CH corresponding to methyl, methylene, and methine, 1600.81 cm -1 and 1507.64 cm -1corresponding to the CH bond on the benzene ring, 1459.07 cm -1 is the methoxy absorption peak, 1331 cm -1 to 1122 cm -1 The stretching vibration peak in the interval is the methoxy absorption peak corresponding to the guaiac ring and the lilac ring, which are the basic substances constituting lignin, 1224.83 cm -1 The corresponding absorption peaks of CC, CO and C=O are 1122.78 cm -1 、1032.22 cm -1 and 872.33cm -1 Corresponding to the CH on the benzene ring. Figure 5 From top to bottom, curve (1) is the infrared spectrum of the dense blank sample; curve (2) is the infrared spectrum of the loose blank sample; curve (3) is the infrared spectrum of the dense reinforced sample after reinforcement; curve (4) is the infrared spectrum of the loose reinforced sample after reinforcement. Curve 3 has an additional 1736 cm compared to curve 1 and curve 4 has an additional 1736 cm compared to curve 2. -1 The characteristic peak of the C=O structure formed by the aromatic ring is analyzed and is the characteristic peak of shellac, indicating that shellac has successfully adhered to the wooden artifacts. Curve 2 has an additional 1421.04 cm-1 compared to Curve 1. -1 The peak was analyzed as a characteristic peak of C=O, indicating that the difference between the two wooden artifacts with different degrees of decay lies in the fact that the honeycomb specimen has more carbonyl peaks on the benzene ring than the block specimen. This is formed by the oxidation of hydroxyl groups on the benzene ring. Therefore, the loose specimen is more oxidized and more decayed than the dense specimen. The infrared spectra of the dense reinforced specimen and the loose reinforced specimen are basically the same, indicating that the functional group composition of the two wooden artifacts after reinforcement is basically the same. The C=O on the aromatic ring of lac and the C=O on the aliphatic chain of PVAc compensate for the C=O functional groups generated by wood oxidation, proving that the reinforcement agent is fully and evenly mixed and successfully covers the surface of the wooden artifact or fills the interior of the wooden artifact, thereby strengthening the wooden artifact.

[0042] Contact angle test (see Appendix Figure 6 )

[0043] Experimental objects: Dense blank and reinforced specimens, loose blank and reinforced specimens were selected from the coffin wood samples unearthed from the Zenghouyi Tomb.

[0044] Experimental method: Contact angle test was performed on the surfaces of dense and loose samples reinforced with the optimal formula.

[0045] Experimental results: Figure 6In the figure, (1) is the contact angle of the dense blank sample; (2) is the contact angle of the loose blank sample; (3) is the contact angle of the dense reinforced sample after reinforcement; and (4) is the contact angle of the loose reinforced sample after reinforcement. The test showed that the hydrophobicity of the dense sample increased by 16.5% before and after reinforcement; the hydrophobicity of the loose sample increased by 9.64% before and after reinforcement. The average hydrophobicity increased by 11.9%. This shows that the PVAc-shellac material has a certain degree of hydrophobicity, and the increase in hydrophobicity varies slightly depending on the decay condition of the wood surface.

[0046] The beneficial effects of the present invention are:

[0047] (1) The prepared composite reinforcement is water-soluble, has good permeability, cures at room temperature, has a simple preparation process, and has good biocompatibility;

[0048] (2) The reinforced wooden cultural relics have good toughness, high strength, small color difference, low surface reflectivity, good durability, and can be reinforced and repaired twice. The overall performance of the product is excellent;

[0049] (3) The methanol solution of PVAc is a water-soluble adhesive. It uses the direct infiltration filling method to form a concentration gradient in the original environment inside the moist wooden cultural relics. It solidifies quickly and moisture will not have much impact on the reinforcement process and reinforcement time. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a picture of wooden cultural relics before reinforcement treatment.

[0051] Figure 2 This is a picture of wooden cultural relics after reinforcement treatment.

[0052] Figure 3 Scanning electron microscope micromorphology images of dense and loose samples before and after reinforcement;

[0053] Figure 4 Infrared spectra of dense and loose samples before and after reinforcement;

[0054] Figure 5 Overlay infrared spectra of dense and loose samples before and after reinforcement;

[0055] Figure 6 Contact angle test diagrams of dense and loose samples before and after reinforcement. DETAILED DESCRIPTION

[0056] First, the degree of decay of wooden cultural relics is evaluated as high, medium, low, or weak based on the water saturation rate.

[0057] Among them, a water saturation rate of 300-400% and above is defined as highly decayed; a water saturation rate of 200-300% is defined as moderately decayed; a water saturation rate of 100-200% is defined as lowly decayed; and a water saturation rate of less than 100% is defined as weakly decayed.

[0058] Example 1 (Wooden cultural relic is highly decayed)

[0059] First, prepare the following raw materials in parts by weight according to the degree of decay of the wooden cultural relic:

[0060] 5 parts of PVAc, 40 parts of methanol, 10 parts of shellac, 27 parts of H2O

[0061] First place methanol in a container, add shellac, and then add H2O2 by dropwise addition. After standing for 5 to 10 minutes, slowly stir to mix the methanol, shellac and H2O2 in the container evenly to form a mixed solution. During the stirring process, the mixed solution in the container gradually changes from colorless to light brown. Then add PVAc and stir to completely dissolve it. The resulting low-viscosity brown colloidal solution is the reinforcing agent.

[0062] Due to the long-term burial of wooden artifacts, their surface color inevitably darkens. A bleaching treatment is performed using a 2-5% by weight oxalic acid solution, sprayed repeatedly in small amounts, with two-hour intervals between each application, until the surface color of the artifact lightens. After bleaching, anhydrous methanol is evenly sprayed onto the surface to cleanse any remaining oxalic acid solution. Two to three applications of methanol are applied, with one-hour intervals between each application. Following this cleaning process, the prepared reinforcement is evenly dripped or sprayed onto the surface of the artifact until the reinforcement is completely absorbed and no droplets remain. The artifact is then dried in a low-humidity environment at 25°C for 8-9 hours. This completes the reinforcement of the wooden artifact. This reinforcement is reversible and reprocessable; the cured reinforcement can be washed off with an appropriate amount of methanol.

[0063] Example 2 (Moderately decayed wooden artifacts)

[0064] First, prepare the following raw materials in parts by weight according to the degree of decay of the wooden cultural relic:

[0065] 5 parts of PVAc, 45 parts of methanol, 8 parts of shellac, 25 parts of H2O

[0066] First place methanol in a container, add shellac, and then add H2O2 by dropwise addition. After standing for 5 to 10 minutes, slowly stir to mix the methanol, shellac and H2O2 in the container evenly to form a mixed solution. During the stirring process, the mixed solution in the container gradually changes from colorless to light brown. Then add PVAc and stir to completely dissolve it. The resulting low-viscosity brown colloidal solution is the reinforcing agent.

[0067] Due to the long-term burial of wooden artifacts, their surface color inevitably darkens. A bleaching treatment is performed using a 2-5% by weight oxalic acid solution, sprayed repeatedly in small amounts, with a 2-hour interval between each bleaching step, until the surface color of the artifact lightens. After bleaching, anhydrous methanol is evenly sprayed onto the surface to cleanse any remaining oxalic acid solution. Two to three applications of methanol are applied, with an interval of one hour between each application. Following this cleaning process, the prepared reinforcement agent is evenly dripped or sprayed onto the surface of the artifact until it is completely penetrated and no droplets remain. The artifact is then dried in a low-humidity environment at 25°C for 8-9 hours. This completes the reinforcement of the wooden artifact. Wooden artifacts reinforced with this reinforcement agent are reversible and reprocessable; the cured material (reinforcement agent) can be dissolved and washed away with methanol.

[0068] Example 3 (Wooden cultural relics with low degree of decay)

[0069] First, prepare the following raw materials in parts by weight according to the degree of decay of the wooden cultural relic:

[0070] 5 parts of PVAc, 50 parts of methanol, 6 parts of shellac, 3 parts of H2O

[0071] First place methanol in a container, add shellac, and then add H2O2 by dropwise addition. After standing for 5 to 10 minutes, slowly stir to mix the methanol, shellac and H2O2 in the container evenly to form a mixed solution. During the stirring process, the mixed solution in the container gradually changes from colorless to light brown. Then add PVAc and stir to completely dissolve it. The resulting low-viscosity brown colloidal solution is the reinforcing agent.

[0072] 4. PVAc 5 parts, Methanol 60 parts, Shellac 4 parts, H2O 21 parts

[0073] Due to the long-term burial of wooden artifacts, their surface color inevitably darkens. A bleaching treatment is performed using a 2-5% by weight oxalic acid solution, sprayed repeatedly in small amounts, with a 2-hour interval between each bleaching step, until the surface color of the artifact lightens. After bleaching, anhydrous methanol is evenly sprayed onto the surface to cleanse any remaining oxalic acid solution. Two to three applications of methanol are applied, with an interval of one hour between each application. Following this cleaning process, the prepared reinforcement agent is evenly dripped or sprayed onto the surface of the artifact until it is completely penetrated and no droplets remain. The artifact is then dried in a low-humidity environment at 25°C for 8-9 hours. This completes the reinforcement of the wooden artifact. Wooden artifacts reinforced with this reinforcement agent are reversible and reprocessable; the cured material (reinforcement agent) can be dissolved and washed away with methanol.

[0074] Example 4 (Weak and decayed wooden cultural relics)

[0075] Prepare the following raw materials in parts by weight according to the degree of decay of the wooden cultural relic:

[0076] 5 parts of PVAc, 60 parts of methanol, 4 parts of shellac, 1 part of H2O

[0077] First place methanol in a container, add shellac, and then add H2O2 by dropwise addition. After standing for 5 to 10 minutes, slowly stir to mix the methanol, shellac and H2O2 in the container evenly to form a mixed solution. During the stirring process, the mixed solution in the container gradually changes from colorless to light brown. Then add PVAc and stir to completely dissolve it. The resulting low-viscosity brown colloidal solution is the reinforcing agent.

[0078] Because wooden artifacts have been buried underground for a long time, their surface color inevitably darkens and becomes black. A 2-5% by weight oxalic acid solution is used for decolorization by spraying in small amounts multiple times, with a 2-hour interval between each decolorization, until the surface color of the wooden artifact becomes lighter. After the decolorization is complete, anhydrous methanol is evenly sprayed on the surface of the wooden artifact to cleanse the residual oxalic acid solution. The number of methanol sprays is 2-3, with an interval of 1 hour between each application. After cleaning, the prepared reinforcement agent is evenly dripped or sprayed on the surface of the wooden artifact until the reinforcement agent is completely penetrated and no droplets remain on the surface. The artifact is then dried in a low-humidity environment at 25°C for 8-9 hours. This completes the reinforcement of the wooden artifact. Wooden artifacts reinforced with this reinforcement agent are reversible and reprocessable; that is, the solidified reinforcement agent can be dissolved and washed away with methanol.

Claims

1. A method for reinforcing water-saturated wooden cultural relics, characterized by: The following steps are included: 1) First, the degree of decay of wooden cultural relics is evaluated as high, medium, low, or weak based on the water saturation rate; 2) Prepare different proportions of reinforcing agents based on the degree of decay of wooden cultural relics of different grades. At the same time, since wooden cultural relics have been buried underground for a long time, their surface color will inevitably become darker and blacker. They need to be bleached by spraying a small amount of 2-5% oxalic acid solution multiple times, with an interval of 2 hours between each bleaching, until the surface color of the wooden cultural relics becomes lighter. 3) After the decolorization treatment is completed, spray anhydrous methanol evenly on the surface of the wooden cultural relics to clean the oxalic acid solution remaining on the surface of the wooden cultural relics. The number of methanol sprays should be 2-3 times, with an interval of 1 hour between each spray. 4) After the reinforcement agent is prepared, evenly drip or spray it on the surface of the wooden cultural relic until the reinforcement agent is completely penetrated and no droplets are hanging on the surface of the wooden cultural relic. Then dry it in a low humidity environment at 25℃ for 8-9 hours. The reinforcement of the wooden cultural relic is then completed. The reinforcing agent is made of the following raw materials in parts by mass: 5 parts of PVAc 40-60 parts of methanol 1-10 parts shellac 1~7 parts H2O2 The preparation method of the reinforcing agent is: According to the above ratio, methanol is first placed in a container, shellac is added, and then H2O2 with a mass concentration of 30% is added dropwise; after standing for 5 to 10 minutes, it is slowly stirred to uniformly mix the methanol, shellac and H2O2 in the container to form a mixed solution. During the stirring process, after the mixed solution in the container gradually changes from colorless to light brown, PVAc is added and stirred to completely dissolve it. The resulting low-viscosity brown colloidal solution is the reinforcing agent; The wooden cultural relics described in step 1) are graded as high, medium, low, and weak, wherein a water saturation rate of 300-400% or above is classified as highly decayed; a water saturation rate of 200-300% is classified as moderately decayed; a water saturation rate of 100-200% is classified as lowly decayed; and a water saturation rate of 100% or below is classified as weakly decayed.

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