KR102648057B1 - Method for processing wood treated with synthetic resin and wax to reduce harmful formaldehyde emission - Google Patents

Abstract

The present invention relates to a wood processing method for treating wood with synthetic resin and wax to reduce harmful formaldehyde emissions. The processing method of the present invention uses a phenolic resin with a low solid content to maximize the improvement of dimensional stability and strength properties. A possible treatment method is double impregnation using a combination of phenol resin and a wax (FT wax) that is not harmful to the human body, and hardening the phenol resin by pressing it in a high-melting-point FT wax solution. This not only promotes hardening, but also promotes hardening in the wood tissue. By introducing and treating with high hardness FT wax, the dimensional stability and strength properties of the processed wood are doubled and the amount of formaldehyde released is suppressed. Therefore, wood processed by the processing method of the present invention can be usefully used as decking material or flooring material.

Description

Method for processing wood treated with synthetic resin and wax to reduce harmful formaldehyde emission}

The present invention relates to a method of processing wood by treating synthetic resin and wax to reduce harmful formaldehyde emissions.

As a response strategy to climate change around the world, policies are being implemented to protect and nurture forests, the only carbon dioxide sink on Earth, and to increase the use of wood, a carbon storage,. The trend of restricting or banning the export of wood is spreading in advanced wood producing countries such as Canada and the United States, as well as Southeast Asian countries with abundant wood resources. In Korea, which relies on imports for more than 80% of its wood demand, it is experiencing difficulties in wood supply and demand. To solve this problem, it is necessary to improve the utilization of domestic wood and develop technology to produce high-quality wood products through reforming treatment of low-quality wood. It is a necessary situation.

Wood modification methods can be broadly classified into chemical treatment methods and physical treatment methods. Representative chemical treatment methods include high heat treatment (hygroscopicity reduction treatment), formalization (acetalization) treatment, esterification (acetylation) treatment, and isocyanate treatment. The purpose of these treatments is to convert the hydrophilic groups (hydroxyl groups) in the wood cell walls into hydrophobic groups. It mainly provides dimensional stability to wood by substituting it, forming cross-links between hydroxyl groups, or thermally decomposing xylose, a 5-carbon sugar that is a component of hemicellulose, among the main components of wood cell walls, and changing it into a hydrophobic material. Physical treatment methods include coating treatment and volumetric treatment. Covering treatment involves applying or injecting waterproof and moisture-proof paint, and volumetric treatment methods include polyethylene glycol (PEG) treatment, wax treatment, and synthetic resin treatment. The volumetric treatment method not only provides dimensional stability by injecting and impregnating materials into the cell walls and cell lumen or gaps of wood tissue, but can also achieve the effect of additionally improving strength properties. Among the volumetric treatment methods, there is a synthetic resin treatment method that can be expected to greatly improve not only dimensional stability but also strength. As synthetic resins, phenol resin, urea resin, resorcinol resin, melamine resin, etc. can be used, but the most commonly used synthetic resin is It is a phenol resin. Phenolic resin not only has excellent water resistance, heat resistance, and weather resistance, but also has low viscosity and is alkaline, so it has good penetration into the wood tissue. Therefore, synthetic resin treated wood refers to phenol resin treated wood and is also called Impreg. For phenol resin treatment, resol type (backlite type A), which is an initial condensate, is used, and a resin with a solid content (non-volatile content) of 30 to 40% is mainly used.

When a phenol resin with a high solid content is used, the properties of the treated wood are excellent, but since a large amount of unreacted formaldehyde used in the production of the resin remains in the resin, the amount of harmful formaldehyde released from the treated wood can be a problem. . To prevent such harm to the human body, there are limits to the amount of formaldehyde released from wood products manufactured using synthetic resins around the world. When a resin with a low solid content used in the treatment of synthetic resins, including phenol resins, is used, the amount of formaldehyde released is reduced, but problems such as low dimensional stability or strength occur, so technology to overcome this is urgently needed.

Meanwhile, as a technology related to wood processing, Korean Patent No. 2175300 discloses a method of manufacturing eco-friendly synthetic wood with enhanced flame retardancy and strength, and Korean Patent No. 1851730 discloses treatment of phenolic resin and strengthening using microwave irradiation. Although a wood processing method has been disclosed, a wood processing method for treating synthetic resin and wax to reduce the harmful formaldehyde emissions of the present invention has not yet been disclosed.

The present invention was developed in response to the above-mentioned needs. The present invention provides a method of processing wood by treating synthetic resin and wax to reduce the amount of harmful formaldehyde released, and the processing method of the present invention provides a method of processing wood using a phenol resin with a low solid content. This is a treatment method that can maximize the improvement of dimensional stability and strength properties by using a double impregnation treatment using a combination of phenol resin and a wax (FT wax) that is not harmful to the human body, and pressurizing the phenol resin in a FT wax solution with a high melting point. Not only does it promote hardening by hardening, but at the same time, by introducing and treating the wood tissue with high-hardness FT wax, it is confirmed that the dimensional stability and strength properties of the processed wood are doubled, and the amount of formaldehyde emissions is suppressed. , completed the present invention.

In order to achieve the above object, the present invention includes the steps of (1) pressurizing and injecting an aqueous synthetic resin solution into wood to be processed;

(2) After step (1), drying the wood injected with the aqueous synthetic resin solution at low temperature and reduced pressure;

(3) After step (2), impregnating the low-temperature, reduced-pressure-dried wood with molten FT (Fischer-Tropsch) wax at 100-130°C to remove moisture remaining in the low-temperature, reduced-pressure-dried wood; and

(4) After step (3), the synthetic resin injected into the wood from which the moisture has been removed is cured at a temperature of 135 to 150°C and a pressure of 1.3 to 1.5 MPa, and the FT wax is infiltrated into the internal structure of the wood, followed by 90 Recovering wood treated with synthetic resin and wax by lowering the temperature and pressure of ~110°C to atmospheric pressure provides a method of processing wood treated with synthetic resin and wax with reduced emissions of harmful formaldehyde, including the step of lowering the temperature and pressure to atmospheric pressure.

In addition, the present invention provides synthetic resin and wax-treated wood with reduced harmful formaldehyde emissions processed by the above processing method.

The present invention relates to a wood processing method for treating wood with synthetic resin and wax to reduce harmful formaldehyde emissions. The processing method of the present invention uses a phenolic resin with a low solid content to maximize the improvement of dimensional stability and strength properties. A possible treatment method is double impregnation using a combination of phenol resin and a wax (FT wax) that is not harmful to the human body, and hardening the phenol resin by pressing it in a high-melting-point FT wax solution. This not only promotes hardening, but also promotes hardening in the wood tissue. By introducing and treating with high hardness FT wax, the dimensional stability and strength properties of the processed wood are doubled and the amount of formaldehyde released is suppressed.

The present invention includes the steps of (1) pressurizing and injecting an aqueous synthetic resin solution into wood to be processed;

(2) After step (1), drying the wood injected with the aqueous synthetic resin solution at low temperature and reduced pressure;

(3) After step (2), impregnating the low-temperature, reduced-pressure-dried wood with molten FT (Fischer-Tropsch) wax at 100-130°C to remove moisture remaining in the low-temperature, reduced-pressure-dried wood; and

(4) After step (3), the synthetic resin injected into the wood from which the moisture has been removed is cured at a temperature of 135 to 150°C and a pressure of 1.3 to 1.5 MPa, and the FT wax is infiltrated into the internal structure of the wood, followed by 90 It relates to a method of processing synthetic resin and wax-treated wood with reduced harmful formaldehyde emissions, including recovering wood treated with synthetic resin and wax by lowering the temperature and pressure of ~110°C to atmospheric pressure.

The wood is preferably radiata pine, but is not limited thereto.

Synthetic resins that can be used in the present invention include urea resin, melamine resin, phenolic resin, or urea-melamine cocondensation resin, but the preferred synthetic resin in the production of synthetic resin-treated wood, which is injected into wood tissue to strengthen the material, is phenolic resin. Phenolic resin is mainly used because it has a lower viscosity than other synthetic resins, has good penetration into the wood structure, has excellent water resistance, and has a superior effect on reinforcing the wood material compared to other synthetic resins. Typically, synthetic resin-treated wood is treated with phenol resin. It was done.

The wax used in the present invention is preferably FT wax, a synthetic wax manufactured using coal or natural gas as a raw material by the Fischer-Tropsch method. FT wax has high crystallinity and linear molecular structure, so it has high hardness and low molecular weight, so it has low viscosity, so it has good penetration into wood and is suitable for reinforcing wood materials. In particular, FT wax has a wide melting point range of 80~115℃ depending on the manufacturing method, and has excellent heat resistance stability at high temperatures.

A preferred example of the processing method of synthetic resin and wax-treated wood with reduced harmful formaldehyde emissions according to the present invention is (1) adding a 10 to 20% (w/v) phenol resin aqueous solution to the radiata pine to be processed at 9 to 18 kgf/ Pressurized injection for 3 to 6 hours at a pressure of ㎠; (2) After step (1), drying the radiata pine injected with 10 to 20% (w/v) of phenol resin aqueous solution at low temperature and reduced pressure at a temperature of 20 to 60°C; (3) After step (2), impregnating the low-temperature, reduced-pressure-dried radiata pine wood with molten FT wax at 100-130°C to remove moisture remaining in the low-temperature, reduced-pressure-dried radiata pine wood; and (4) after step (3), the phenolic resin injected into the dehydrated radiata pine is cured under a temperature of 135 to 150°C and a pressure of 1.3 to 1.5 MPa, and the FT wax penetrates into the internal tissue of the radiata pine. A method of processing synthetic resin and wax-treated wood with reduced harmful formaldehyde emissions, including recovering the radiata pine treated with phenolic resin and wax by lowering the temperature and pressure of 90 to 110°C to atmospheric pressure, but limited thereto. don't do it,

Looking at the steps of the above processing method in detail,

Step 1: The pressure injection method of the synthetic resin aqueous solution is processed using the normal filling method used in wood chemical treatment. The pressurized injection step of the synthetic resin aqueous solution of the present invention is ① inserting dry wood into the main container and sealing it → ② depressurizing the inside of the main container and exhausting it (650-700 mmHg, 30-60 minutes) → ③ injecting the synthetic resin aqueous solution into the main container (main Fill the inside of the container with aqueous solution) → ④ Push the synthetic resin aqueous solution into the main container using a pressurized pump (pressure force 9~18kgf/㎠, 3~6 hours) → ⑤ Stop the pressure → ⑥ Recover the synthetic resin aqueous solution → ⑦ Main container It consists of the following steps: depressurizing the inside, post-exhausting (650~700mmHg, 30~60 minutes), recovering the excessively injected synthetic resin solution → ⑧ normal pressure → ⑨ recovering wood into which the synthetic resin solution was pressurized.

Step 2: This is a low-temperature, reduced-pressure drying step for wood pressure-injected with synthetic resin. Since wood that has been pressure-injected with a synthetic resin aqueous solution has a high moisture content of over 100%, this is a drying step in which moisture is removed through reduced pressure at a low temperature of 60°C or lower. If dried at a high temperature exceeding 60℃, deformations such as splitting and distortion due to material shrinkage occur, so reduced pressure drying is performed to shorten the drying time at a low temperature below 60℃. After going through the low-temperature, reduced-pressure drying step, the moisture content of wood pressure-injected with a synthetic resin aqueous solution decreases to an average of 40-50%, and only a small amount of moisture and uncured synthetic resin remain in the cell walls, cell lumen, and gaps of the wood tissue. do. The low-temperature, reduced-pressure drying step according to the present invention is ① inserting high moisture content wood into which a synthetic resin aqueous solution has been pressurized and sealed into the main container → ② setting the temperature inside the main container to a range of 50 to 60°C → ③ decompressing (650 to 700 mmHg, 6 It consists of the following steps (~12 hours, decompression drying time varies depending on the volume of wood) → ④ decompression stop → ⑤ normal pressure → ⑥ recovery of treated wood.

Step 3 is a drying step that completely removes the remaining moisture remaining after drying the synthetic resin pressurized wood in a FT wax solution melted at 120°C at low temperature and under reduced pressure.

When heat (dry heat) drying (drying using hot air) above 100℃ is performed, a large temperature difference occurs between the surface and the interior of the wood due to the low thermal conductivity of the wood, resulting in fine cracks on the surface of the material due to the stress difference and damage to the surface of the material. Heat deterioration occurs, causing the color of the wood to turn brown (the larger the wood, the longer it takes to dry, and the temperature difference between the surface layer and the interior is large, causing severe deformation and discoloration).

When impregnated in a high-temperature molten FT wax solution and dried, the moisture contained in the wood tissue (especially the surface layer) evaporates and at the same time, the wax penetrates into the area where the moisture was. In other words, the moisture is replaced by wax, thereby suppressing deformation such as fine splitting. do. In addition, the wax prevents oxygen (air) from contacting the surface of the material, preventing discoloration (browning) from occurring due to oxidation. The synthetic resin (phenol resin) used in step 3 of the present invention is characterized by not being hardened (phenol resin curing temperature 135-145°C).

The three steps of high temperature and normal pressure drying of synthetic resin pressure-injected wood of the present invention are ① impregnating low-temperature, reduced-pressure dried synthetic resin pressure-injected wood into a molten wax bath installed in the main container → ② maintaining the molten wax temperature at 120°C and generating air bubbles from the wood. It consists of the step of heat treatment until there is no moisture (moisture is also evaporated).

Step 4 is the resin curing and wax introduction stage of the synthetic resin pressure-injected wood. This is a treatment stage in which the uncured synthetic resin remaining in the wood tissue is completely cured and FT wax is injected into the wood tissue to strengthen the material.

The temperature of the wax solution is raised to the curing temperature of the synthetic resin, and then pressurized to allow the high-temperature FT wax to penetrate into the wood tissue, simultaneously heating and hardening the surface layer of the wood and the synthetic resin remaining inside the tissue. Only the temperature of the wax solution is raised to the curing temperature and the normal pressure is maintained. If maintained, the synthetic resin in the surface layer of the wood will harden, but the synthetic resin that has penetrated into the wood structure will delay hardening due to slow heat transfer. However, when pressure is applied, FT wax, which has a resin hardening temperature, penetrates into the wood tissue, and heat is quickly transferred, promoting hardening. Specifically, ① After confirming that no bubbles are generated from the wood impregnated with molten wax at a temperature of about 120℃, the main container door is closed and sealed → ② After setting the internal temperature of the main container at 140℃, compressed gas is introduced into the main container. Gradually introduce and raise the internal pressure to 1.5MPa (as the pressure rises, the internal temperature of the main chemical vessel gradually rises and rises by 5~10℃ above the set temperature) → ③ The internal pressure of the main chemical vessel is checked in real time, and when the pressure drops, compressed gas is supplied. Initial pressure (1.5MPa) is maintained by additional introduction → ④ The temperature inside the main chemical vessel rises to 145~150℃, maintained for 1~2 hours → ⑤ The internal temperature of the main chemical vessel is lowered to about 100℃ → ⑤ It consists of the steps of gradually lowering the pressure inside the main chamber to atmospheric pressure → ⑥ opening the main chamber and recovering the treated wood.

In addition, the present invention relates to synthetic resin and wax-treated wood with reduced harmful formaldehyde emissions processed by the above processing method. The formaldehyde emission amount of the wood is less than 0.07 mg/L, and it has excellent dimensional stability, bending strength, and surface hardness.

Wood according to the above processing method is preferably used as decking material or flooring material, but is not limited thereto.

Hereinafter, the present invention will be described in more detail using examples. These examples are only for illustrating the present invention in more detail, and it is obvious to those skilled in the art that the scope of the present invention is not limited thereto.

<Example 1>

The wood species used was New Zealand radiata pine, which is imported in large quantities into Korea. Radiata pine is a fast-growing tree, so its annual rings are wide and its material is relatively weak, making it a low-grade wood. This species is very suitable for verifying the material strengthening effect by double impregnation of phenolic resin and FT wax. An industrial phenol resin with a non-volatile content of 43% was purchased and used by diluting it with tap water so that the non-volatile content was 10% or 20%.

In the production of synthetic resin-treated wood, phenolic resin is mainly used, which has a low viscosity compared to other synthetic resins, good penetration into wood tissue, and excellent water resistance, which has a good effect on reinforcing the wood material. Therefore, phenolic resin was also used in the examples of the present invention.

Dimensional stability was measured and compared according to the wood water absorption measurement method of KS F 2204 and the wood shrinkage test method of KS F 2203, the bending strength was measured by the wood bending test method of KS F 2208, and the surface hardness was measured by the wood bending test method of KS F 2212. Hardness was measured and compared according to the test method, and formaldehyde emission was measured and compared using the desiccator method of KS M 1998.

As a result, Tables 1 to 3 show comparative results for dimensional stability (Table 1), bending strength and surface hardness (Table 2), and formaldehyde emission (Table 3).

Dimensional stability
Processing method radiata pine absorption amount volumetric shrinkage Absorption amount (g/㎠) Decrease rate (%) Shrinkage rate (%) Decrease rate (%) Untreated 0.17 - 5.4 - Phenolic resin 10% aqueous solution treatment alone 0.12 29.4 3.8 29.6 Phenolic resin 20% aqueous solution treatment alone 0.14 17.6 4.1 24.1 10% phenolic resin + FT wax double impregnation treatment 0.03 82.4 3.4 37.0 20% phenolic resin + FT wax double impregnation treatment 0.03 82.4 2.4 55.6

Comparing the moisture absorption by treatment method of radiata pine, it can be seen that both phenolic resin alone and phenolic resin-FT wax double impregnation treatment have less moisture absorption than untreated wood, creating a hydrophobic substance that inhibits moisture penetration into the wood tissue. . In particular, when treated with FT wax compared to phenolic resin alone, the effect of suppressing moisture penetration into the wood tissue is excellent, reducing moisture absorption by more than 80% compared to untreated wood and more than 75% compared to wood treated with phenolic resin alone. This contributed to improving dimensional stability.

By injecting and curing a high-temperature FT wax solution rather than pressurizing and curing the phenol resin after injecting it, the wax fills the cell lumen and gaps along with the cured phenol resin in the wood tissue, resulting in a synergistic effect of suppressing moisture penetration. You can judge. The shrinkage inhibition effect also showed excellent results in the phenol resin-FT wax double impregnation treatment compared to the phenol resin treatment alone. In the case of phenol resin treatment alone, the phenol resin penetrates into the wood cell walls and hardens, and the cell lumen or gap remains empty, so the effect of inhibiting shrinkage is small. However, by pressurizing the injection of FT wax to harden the phenol resin, the hardened phenol resin is contained in the cell walls. , the cell lumen or gap was filled with FT wax, and the shrinkage inhibition effect was increased due to the volume effect (filling effect).

Bending strength and surface hardness
Processing method radiata pine Bending strength surface hardness Strength (N/㎟) Increase rate (%) Hardness (N/㎟) Increase rate (%) Untreated 67.4 - 11.6 - Phenolic resin 10% aqueous solution treatment alone 77.5 15.0 21.1 82.0 Phenolic resin 20% aqueous solution treatment alone 75.7 12.3 26.6 129.3 10% phenolic resin + FT wax double impregnation treatment 86.6 28.5 34.2 194.8 20% phenolic resin + FT wax double impregnation treatment 85.1 26.3 40.6 250.0

Wood treated with phenol resin-FT wax double impregnation had a high-density structure in which FT wax with high hardness was injected into the wood structure in addition to the hardened phenol resin and solidified, resulting in increased bending strength and surface hardness. In particular, the rate of increase in surface hardness is remarkable, making it possible to manufacture wooden products with excellent wear resistance, making it suitable for manufacturing flooring materials such as decking materials and flooring materials.

formaldehyde emissions
Processing method radiata pine Emission amount (mg/L) Decrease rate (%) Phenolic resin 10% aqueous solution treatment alone 0.14 - Phenolic resin 20% aqueous solution treatment alone 0.41 - 10% phenolic resin + FT wax double impregnation treatment 0.07 50.0 20% phenolic resin + FT wax double impregnation treatment 0.05 37.8

The quality standards for formaldehyde emissions from wood products in Korea are divided into SE0 (emissions of 0.3 mg/L or less), E0 (emissions of 0.3 to 0.5 mg/L), E1 (emissions of 0.5 to 1.5 mg/L), and E0. The above products are recognized as eco-friendly.

Formaldehyde is known to be a carcinogen, and since unreacted formaldehyde is released from wood products using synthetic resins, the amount released is strictly regulated. In the case of phenol resin treatment alone, 10% of non-volatile matter is in the SE0 grade, but in the case of 20% non-volatile matter, the emission level is E0 grade, and in the phenol resin-FT wax double impregnation treatment, the harmful formaldehyde emission is significantly reduced, so that it is SE0 grade or higher. It appears to have quality.

The FT wax layer acts as a coating agent on the cured phenol resin, showing the effect of suppressing the release of unreacted formaldehyde from the cured phenol resin layer.

When trying to strengthen the material by using phenolic resin in wood of poor quality, by pressurizing and curing FT wax with a high melting point rather than injecting phenolic resin and then curing it with heat, the bending strength and surface are improved in addition to dimensional stability against moisture. Not only can the effect of increasing strength properties such as hardness be obtained, but it also has the effect of suppressing formaldehyde emission, making it possible to manufacture high-quality wood products.

Claims (7)

(1) pressure-injecting an aqueous synthetic resin solution into the wood to be processed;
(2) After step (1), drying the wood injected with the aqueous synthetic resin solution at low temperature and reduced pressure;
(3) After step (2), impregnating the low-temperature, reduced-pressure dried wood with molten FT (Fischer-Tropsch) wax at 100-130°C to remove moisture remaining in the low-temperature, reduced-pressure dried wood; and
(4) After step (3), the synthetic resin injected into the wood from which the moisture has been removed is cured at a temperature of 135 to 150°C and a pressure of 1.3 to 1.5 MPa, and the FT wax is infiltrated into the internal structure of the wood, followed by 90 Recovering wood treated with synthetic resin and wax by lowering the temperature and pressure of ~110°C to atmospheric pressure. A method of processing wood treated with synthetic resin and wax with reduced emissions of harmful formaldehyde, including: The method of claim 1, wherein the wood is radiata pine. The method of claim 1, wherein the synthetic resin is one selected from urea resin, melamine resin, phenol resin, and urea-melamine cocondensation resin. According to paragraph 1,
(1) Injecting a 10 to 20% (w/v) phenol resin aqueous solution into the radiata pine to be processed at a pressure of 9 to 18 kgf/cm2 for 3 to 6 hours;
(2) After step (1), drying the radiata pine injected with 10 to 20% (w/v) of phenol resin aqueous solution at low temperature and reduced pressure at a temperature of 20 to 60°C;
(3) After step (2), impregnating the low-temperature, reduced-pressure-dried radiata pine wood with molten FT wax at 100-130°C to remove moisture remaining in the low-temperature, reduced-pressure-dried radiata pine wood; and
(4) After step (3), the phenol resin injected into the radiata pine tree from which the moisture was removed was cured under a temperature of 135 to 150°C and a pressure of 1.3 to 1.5 MPa, and the FT wax was infiltrated into the internal tissue of the radiata pine tree. Then, recovering the radiata pine treated with phenol resin and wax by lowering the temperature and pressure of 90 to 110°C to atmospheric pressure. A method of processing synthetic resin and wax-treated wood with reduced harmful formaldehyde emissions, including: Synthetic resin and wax-treated wood with reduced harmful formaldehyde emissions, processed by any one of the processing methods selected from claims 1 to 4. The synthetic resin and wax-treated wood with reduced harmful formaldehyde emissions according to claim 5, wherein the formaldehyde emission of the wood is 0.07 mg/L or less. The synthetic resin and wax-treated wood with reduced harmful formaldehyde emissions according to claim 5, wherein the wood is a decking material or a flooring material.