A wood dimensional stability modifier and its use

Abstract

The application discloses a wood dimensional stability modifier, which is composed of the following components in percentage by mass: 7-12% of magnesium chloride, 1-2% of sodium hydroxide, 3-5% of ethyl orthosilicate, 4-7% of polyethylene glycol, 1-1.5% of sodium lignosulfonate, and the balance of water; and the wood dimensional stability modifier is used for improving the wood dimensional stability. The wood dimensional stability modifier adopts cheap raw materials, utilizes the synergistic effect among the raw materials, improves the effect of the magnesium chloride on the wood dimensional stability improvement, and further obtains a modified application method which is good in stability and low in cost.

Description

Technical Field

[0001] This invention relates to a method for modifying wood, specifically to a wood dimensionally stable modifier and its application. Background Technology

[0002] Fast-growing timber from plantations, due to its short growth and rotation cycles and high proportion of young timber, inevitably suffers from poor quality, susceptibility to corrosion, low density, low strength, and easy cracking and deformation. Its mechanical properties and dimensional stability fail to meet usage requirements, significantly limiting its applications. It is typically used as raw material for fiberboard, particleboard, plywood, and other engineered wood products, indirectly used in furniture and other fields, or as raw material for papermaking and construction templates. Therefore, research on the dimensional stability of fast-growing timber is crucial. Common methods include high-temperature thermal modification, compression densification, chemical modification, and impregnation modification. Impregnation modification utilizes vacuum or pressure impregnation methods to add modifiers into the wood, causing physical adsorption or filling within the wood, sealing cell cavities or swelling cell walls, increasing the bulk density of the wood, and thus improving its properties. Depending on the type of modifier, impregnation modification can be categorized into waterproofing agent impregnation, polyethylene glycol impregnation, resin impregnation, and silicon-containing compound impregnation. Silicon-containing compound impregnation treatment usually utilizes organosiloxanes, organosilanes, etc. to form silica sol, which forms stable Si-O-C and Si-O-Si chemical bonds with wood, and at the same time produces a condensation reaction. Therefore, the hygroscopicity and water absorption of the treated wood are reduced, and the dimensional stability is increased.

[0003] In existing technologies, silica-containing solvents such as tetraethyl orthosilicate, along with some additives, are impregnated into wood under vacuum pressure to improve its properties. However, for industrial production, tetraethyl orthosilicate, organosiloxanes, or organosilane solvents are too expensive. To reduce costs, the amount added is reduced to improve the wood, but the resulting wood properties are unsatisfactory. While treating with cheaper hydrated metal salts such as magnesium chloride hexahydrate shows some modification, the effect is still insufficient. Therefore, there is an urgent need for a cost-effective method that produces wood with good properties after treatment. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a wood dimensional stability modifier, using magnesium chloride as the main agent, tetraethyl silicate as an auxiliary agent, and polyethylene glycol (PEG) and sodium lignosulfonate as crosslinking agents to improve wood dimensional stability, aiming to obtain a modification method with good stability and low cost.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0006] A wood dimensional stabilizer modifier, comprising, by mass percentage, the following components: 7%–12% magnesium chloride hexahydrate, 1%–2% sodium hydroxide, 3%–5% tetraethyl orthosilicate, 4%–7% polyethylene glycol (molecular weight 600), 1%–1.5% sodium lignosulfonate, with the balance being water.

[0007] The use of wood dimensional stabilizers as described above to improve wood dimensional stability includes the following steps:

[0008] (1) Fast-growing timber should be left to air dry after felling;

[0009] (2) Preparation of the modifier: Take the following components by mass percentage: 7% to 12% magnesium chloride hexahydrate, 1% to 2% sodium hydroxide, 3% to 5% tetraethyl orthosilicate, 4-7% polyethylene glycol (molecular weight 600), 1-1.5% sodium lignosulfonate, and the balance is water;

[0010] (3) Vacuum-pressure impregnation: The air-dried wood in step (1) is placed in the modifier prepared in step (2) and impregnated under vacuum; the entire vacuum impregnation process is repeated 2 to 3 times to ensure that the wood is impregnated to saturation.

[0011] (4) Drying: After depressurization, take out the impregnated wood and place it in a forced-air drying environment of 30℃~40℃ for 36~48h (if the modifier is directly dried at high temperature, it is easy for the surface to react but the inside to not react. The modifier is also very hydrophilic, and if not handled properly, the wood will easily absorb water in the later stage); then adjust the forced-air drying temperature to 60~90℃ and continue drying for 2~4h to obtain improved wood with high dimensional stability.

[0012] Preferably, in step (3), the impregnation under vacuum is performed by maintaining a vacuum of -0.06 to -0.1 MPa for 4 to 6 hours to fully soak the wood, and then adjusting the vacuum to 0.5 to 0.8 MPa and continuing the impregnation for 6 to 24 hours.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] The wood dimensional stabilizer modifier of this invention uses inexpensive raw materials. By utilizing the synergistic effect between the raw materials, the effect of magnesium chloride on improving the dimensional stability of wood is enhanced, thereby obtaining a modification application method with good stability and low cost. Attached Figure Description

[0015] Figure 1 These are images showing the effect after 8 pieces of red pine wood have been treated with water and dried.

[0016] Figure 2 These are the effect diagrams of the wood after water saturation treatment and drying obtained in Examples 1-7.

[0017] Figure 3 Images of the improved wood samples (20×20×20mm) with high dimensional stability prepared in Examples 1-4 after standing for three days.

[0018] Figure 4 Image A shows four modified wood samples (20×20×20mm) obtained from Comparative Example 2 after being left to stand for three days. Figure 4 B is Figure 3 Enlarged view of the wood sample on the right. Detailed Implementation

[0019] The specific embodiments are described in detail below with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise specified, the raw materials and reagents used in the embodiments are commercially available. The fast-growing forest timber used in the embodiments is Guangxi red pine with high growth stress, harvested at the Fubo Experimental Field of the Tropical Forestry Experimental Center of the Chinese Academy of Forestry in Pingxiang City, Guangxi.

[0020] Example 1

[0021] A method for improving wood using a wood-dimensionally stabilizing modifier, comprising the following steps:

[0022] (1) After the red pine trees are felled, they are left to air dry and then sawn into red pine wood pieces with dimensions of 200×20×100mm.

[0023] (2) Preparation of modifier: The total amount of modifier prepared is 20L, and the proportions of each component are as follows: magnesium chloride hexahydrate 7% (mass fraction), sodium hydroxide 1% (mass fraction), tetraethyl orthosilicate 3% (mass fraction), polyethylene glycol (molecular weight 600) 4% (mass fraction), sodium lignosulfonate 1% (mass fraction), and the remainder is water;

[0024] (3) Vacuum-pressure impregnation: The red pine wood obtained after sawing in step (1) is placed in a vacuum-pressure impregnation tank. The modifier prepared in step (2) is drawn into the vacuum-pressure impregnation tank. The vacuum-pressure impregnation tank is evacuated to -0.06 MPa. The wood is impregnated at this vacuum level for 6 hours to fully soak it. Then the pressure is increased to 0.5 MPa and impregnated for 24 hours. The entire vacuum impregnation process is repeated twice (i.e., impregnating at -0.06 MPa for 6 hours, then pressurizing to 0.5 MPa and impregnating for 24 hours, this is one time. Then the same vacuum impregnation operation is repeated again) to ensure that the wood is impregnated to a saturated state.

[0025] (4) Drying: After depressurizing and removing the impregnated wood, it is placed in a forced-air drying environment at 30°C for 42 hours; then the forced-air drying temperature is adjusted to 60°C and the drying continues for 4 hours to obtain improved wood with high dimensional stability.

[0026] Example 2

[0027] A method for improving wood using a wood-dimensionally stabilizing modifier, comprising the following steps:

[0028] (1) After the red pine trees are felled, they are left to air dry and then sawn into red pine wood pieces with dimensions of 200×20×100mm.

[0029] (2) Preparation of modifier: The total amount of modifier prepared is 20L, and the proportions of each component are as follows: magnesium chloride hexahydrate 8% (mass fraction), sodium hydroxide 1.5% (mass fraction), tetraethyl orthosilicate 3.5% (mass fraction), polyethylene glycol (molecular weight 600) 4.5% (mass fraction), sodium lignosulfonate 1.1% (mass fraction), and the remainder is water;

[0030] (3) Vacuum-pressure impregnation: The red pine wood obtained after sawing in step (1) is placed in a vacuum-pressure impregnation tank. The modifier prepared in step (2) is drawn into the vacuum-pressure impregnation tank. The vacuum-pressure impregnation tank is evacuated to 0.1 MPa. The wood is impregnated at this vacuum level for 4 hours to fully soak it. Then the pressure is increased to 0.8 MPa and impregnated for 6 hours. The entire vacuum impregnation process is repeated 3 times (i.e., impregnating at 0.1 MPa for 4 hours, then pressurizing to 0.8 MPa and impregnating for 6 hours, which is 1 time. Then the same vacuum impregnation operation is repeated 2 times to ensure that the wood is impregnated to a saturated state).

[0031] (4) Drying: After depressurizing and removing the impregnated wood, it is placed in a forced-air drying environment at 40°C for 48 hours; then the forced-air drying temperature is adjusted to 70°C and the drying continues for 4 hours to obtain improved wood with high dimensional stability.

[0032] Example 3

[0033] A method for improving wood using a wood-dimensionally stabilizing modifier, comprising the following steps:

[0034] (1) After the red pine trees are felled, they are left to air dry and then sawn into red pine wood pieces with dimensions of 200×20×100mm.

[0035] (2) Preparation of modifier: The total amount of modifier prepared is 20L, and the proportions of each component are as follows: magnesium chloride hexahydrate 9% (mass fraction), sodium hydroxide 1.5% (mass fraction), tetraethyl orthosilicate 3.5% (mass fraction), polyethylene glycol (molecular weight 600) 4.5% (mass fraction), sodium lignosulfonate 1.3% (mass fraction), and the remainder is water;

[0036] (3) Vacuum-pressure impregnation: The red pine wood obtained after sawing in step (1) is placed in a vacuum-pressure impregnation tank. The modifier prepared in step (2) is drawn into the vacuum-pressure impregnation tank. The vacuum-pressure impregnation tank is evacuated to -0.08 MPa. Then, the wood is impregnated at this vacuum level for 5 hours to fully soak it. Then, the pressure is increased to 0.6 MPa and impregnated for 15 hours. The entire vacuum impregnation process is repeated 3 times (i.e., -0.08 MPa, then impregnated at this vacuum level for 5 hours, then pressure increased to 0.6 MPa and impregnated for 15 hours, this is 1 time. Then the same vacuum impregnation operation is repeated 2 more times) to ensure that the wood is impregnated to a saturated state.

[0037] (4) Drying: After depressurizing and removing the impregnated wood, it is placed in a forced-air drying environment at 35°C for 36 hours; then the forced-air drying temperature is adjusted to 90°C and the drying continues for 4 hours to obtain improved wood with high dimensional stability.

[0038] Example 4

[0039] (2) Preparation of modifier: The total amount of modifier prepared is 20L, and the proportions of each component are as follows: magnesium chloride hexahydrate 10% (mass fraction), sodium hydroxide 1.5% (mass fraction), tetraethyl orthosilicate 4% (mass fraction), polyethylene glycol (molecular weight 600) 4.5% (mass fraction), sodium lignosulfonate 1.1% (mass fraction), and the remainder is water;

[0040] The remaining operations are the same as in Example 1.

[0041] Example 5

[0042] (2) Preparation of modifier: The total amount of modifier prepared is 20L, and the proportions of each component are as follows: magnesium chloride hexahydrate 12% (mass fraction), sodium hydroxide 2% (mass fraction), tetraethyl orthosilicate 5% (mass fraction), polyethylene glycol (molecular weight 600) 7% (mass fraction), sodium lignosulfonate 1.5% (mass fraction), and the remainder is water; the rest of the operation is the same as in Example 1.

[0043] Example 6

[0044] (2) Preparation of modifier: The total amount of modifier prepared is 20L, and the proportions of each component are as follows: magnesium chloride hexahydrate 12% (mass fraction), sodium hydroxide 1.7% (mass fraction), tetraethyl orthosilicate 5% (mass fraction), polyethylene glycol (molecular weight 600) 5% (mass fraction), sodium lignosulfonate 1.5% (mass fraction), and the remainder is water;

[0045] The remaining operations are the same as in Example 1.

[0046] Example 7

[0047] (2) Preparation of modifier: The total amount of modifier prepared is 20L, and the proportions of each component are as follows: magnesium chloride hexahydrate 11% (mass fraction), sodium hydroxide 1.5% (mass fraction), tetraethyl orthosilicate 5% (mass fraction), polyethylene glycol (molecular weight 600) 5% (mass fraction), sodium lignosulfonate 1.3% (mass fraction), and the remainder is water;

[0048] The remaining operations are the same as in Example 1.

[0049] Comparative Example 1

[0050] After the red pine trees were felled, they were air-dried and then sawn into pieces measuring 200×20×100mm. Eight pieces of red pine wood (i.e., the red pine wood obtained after sawing was not treated in any way) were tested.

[0051] Water saturation treatment: The wood is placed in a vacuum pressure impregnation tank, and water is drawn into the tank until it is full. The vacuum pressure impregnation tank is then evacuated to -0.08 MPa and maintained at this vacuum level for 5 hours to fully saturate the wood. Then the pressure is increased to 0.8 MPa and maintained for 24 hours. The entire process is repeated 3 times to ensure that the wood is fully saturated.

[0052] After the wood from Comparative Example 1 and Examples 1-7 was saturated with water, it was directly placed in an oven at 103°C for 12 hours to dry, and the results were as follows. Figure 1 and Figure 2 :

[0053] Figure 1 As can be seen from Example 1, many cracks and deformations have occurred.

[0054] Figure 2 The results of the embodiments (from left to right are embodiments 1-7) show that there is no cracking or deformation.

[0055] Comparative Example 2

[0056] Four treatments were set up: Treatment ① was based on Example 1, with step (4) drying: after depressurizing and taking out the impregnated wood, it was placed at 60°C and dried by forced air for 12 hours to obtain the improved wood; the rest of the operation was the same as in Example 1.

[0057] Processing ② is based on Example 2. Step (4) Drying: After depressurizing and removing the impregnated wood, it is placed in a 70°C blower to dry for 10 hours to obtain improved wood; the remaining operations are the same as in Example 2.

[0058] Processing ③ is based on Example 3. Step (4) Drying: After depressurizing and taking out the impregnated wood, it is placed in a 90°C blower to dry for 10 hours to obtain improved wood; the remaining operations are the same as in Example 1.

[0059] Processing ④ is based on Example 4. Step (4) Drying: After depressurizing and taking out the impregnated wood, it is placed at 90°C and dried by forced air for 10 hours to obtain improved wood; the remaining operations are the same as in Example 4.

[0060] The wood obtained from each of Examples 1-4, and the wood obtained from the four treatments in Comparative Example 2, were cut into 20×20×20mm samples and left to stand for three days. The wood samples from Examples 1-4 were observed to resemble... Figure 3 As shown (from left to right, Examples 1 to 4), the four wood samples obtained from the treatment of Comparative Example 2 are as follows: Figure 4 As shown (from left to right, these are processes ①, ②, ③, and ④ of Example 2). From Figure 3 As can be seen, the wood color of Examples 1-4 of the present invention remains unchanged, while the wood obtained from the four treatments in Comparative Example 2 absorbs moisture severely and appears entirely black. Figure 4 B shows obvious water droplets on the surface of the wood sample.

[0061] Comparative Example 3

[0062] (2) Preparation of modifier: The total amount of modifier prepared is 20L, and the proportions of each component are as follows: sodium hydroxide 2% (mass fraction), tetraethyl orthosilicate 5% (mass fraction), polyethylene glycol (molecular weight 600) 7% (mass fraction), sodium lignosulfonate 1.5% (mass fraction), and the remainder is water;

[0063] The remaining operations are the same as in Example 1.

[0064] Comparative Example 4

[0065] (2) Preparation of modifier: The total amount of modifier prepared is 20L, and the proportions of each component are as follows: magnesium chloride hexahydrate 12% (mass fraction), sodium hydroxide 2% (mass fraction), polyethylene glycol (molecular weight 600) 7% (mass fraction), sodium lignosulfonate 1.5% (mass fraction), and the remainder is water;

[0066] The remaining operations are the same as in Example 1.

[0067] Comparative Example 5

[0068] (2) Preparation of modifier: The total amount of modifier prepared is 20L, and the proportions of each component are as follows: magnesium chloride hexahydrate 12% (mass fraction), sodium hydroxide 2% (mass fraction), tetraethyl orthosilicate 5% (mass fraction), and the remainder is water;

[0069] The remaining operations are the same as in Example 1.

[0070] The dimensional stability of the wood prepared in Example 7 and Comparative Examples 3-5 was tested using the following method: The wood obtained in each example was cut to the specified dimensions, and the dimensional stability test specimens (axial × tangential × radial) were 20mm × 20mm × 20mm, with 10 specimens per group. First, the specimens were dried to absolute dryness, and the dimensions in three directions were tested. Then, a constant temperature and humidity chamber was used for equilibration treatment, with the temperature and humidity set to "temperature 20℃ - relative humidity 65%". After the moisture content of the specimens reached equilibrium, the dimensions were measured again. The expansion resistance (EAS) of the wood was calculated according to the national standard GB / T 1934.2—2009 "Method for Determination of Wood Swelling". The results are shown in the table below:

[0071] Example 7 32.83 Comparative Example 3 26.74 Comparative Example 4 19.16 Comparative Example 5 22.21

[0072] As can be seen from Table 1, the improved wood obtained by the method of the present invention has a greater volume expansion resistance, indicating better dimensional stability.

[0073] This invention employs inexpensive chemical agents (magnesium chloride hexahydrate, polyethylene glycol, etc.) for treatment, using magnesium chloride as the main agent and tetraethyl orthosilicate as an auxiliary agent. Magnesium chloride is a preservative with good moisture-proof properties, which can significantly reduce the water absorption rate of wood, but its effect is not as good as that of silica-containing sols. PEG and sodium lignosulfonate are used to increase the cross-linking degree of the sol particles, and the polyethylene glycol and silica network, together with magnesium chloride, enhance the dimensional stability of the wood. Under the modifiers specified in this invention, the method of this invention can improve the effect of magnesium chloride on improving the dimensional stability of wood.

[0074] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. The application of a wood dimensional stabilizer modifier in improving the dimensional stability of wood, characterized in that, The modifier is composed of the following components by mass percentage: 7%~12% magnesium chloride, 1%~2% sodium hydroxide, 3%~5% tetraethyl orthosilicate, 4%~7% polyethylene glycol, 1%~1.5% sodium lignosulfonate, and the balance is water; The wood dimensional stabilizer modifier is used to improve the dimensional stability of wood and includes the following steps: (1) Fast-growing timber should be left to air dry after felling; (2) Preparation of modifier: Take the following components by mass percentage: 7%~12% magnesium chloride, 1%~2% sodium hydroxide, 3%~5% tetraethyl orthosilicate, 4-7% polyethylene glycol, 1~1.5% sodium lignosulfonate, and the remainder is water; (3) Vacuum-pressure impregnation: The air-dried wood in step (1) is placed in the modifier prepared in step (2) and impregnated under vacuum conditions; the entire vacuum impregnation process is repeated 2 to 3 times. (4) Drying: After removing the impregnated wood, dry it at 30℃~40℃ for 36~48h; then adjust the drying temperature to 60~90℃ and continue drying for 2~4h to obtain improved wood with high dimensional stability.

2. The application according to claim 1, characterized in that: In step (3), the immersion under vacuum conditions is to maintain a vacuum of -0.06 to -0.1 MPa for 4 to 6 hours, and then adjust the vacuum to 0.5 MPa to 0.8 MPa and continue immersion for 6 to 24 hours.

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