A wood debarking process

Abstract

A wood degreasing process, comprising the following steps: providing a degreasing promoting liquid; pretreatment: soaking wood in the degreasing promoting liquid for 0.5-3.5 hours; heat treatment: taking the wood out of the degreasing promoting liquid and placing it into a carbonization kiln; wood repairing treatment: providing a curing agent, dissolving the curing agent in a solvent to form a repairing agent solution, and then soaking the wood after the heat treatment into the repairing agent solution; and lumber drying treatment: drying the wood after the modification treatment to complete the degreasing of the wood. The degreasing process uses the degreasing promoting liquid in the early stage of degreasing and adopts a low-temperature weak alkaline solution, which can make the resin precipitate from the wood and undergo saponification reaction with the alkaline substance provided by the sodium bicarbonate, so as to achieve the purpose of removing the resin, and at the same time, the temperature of the heat treatment can be reduced and the speed of the heat treatment can be increased, so that the heat treatment can be carried out at medium temperature, thereby reducing the influence on the color and mechanical properties of the wood and improving the stability of the product.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wood processing, in particular to a wood degreasing process. BACKGROUND

[0002] The wood of Pinus, Picea, Larix, Pseudotsuga, Abies and Cathaya has normal resin ducts in its structure, secretes resin, and has rich resin content. In the process of wood processing and utilization, high content of resin will affect the sawing, sanding, painting and gluing processes of wood. In addition, when the environmental temperature is relatively high, the resin will also seep out to the surface of the wood, polluting the wood products. Therefore, the wood needs to be degreased during the processing and utilization process to improve its processing performance and surface quality and expand its application range.

[0003] At present, various pine or fir wood has slightly different degreasing methods due to their characteristics, fat content and different inclusions, but the current wood degreasing methods and processes can be summarized into five kinds: (1) alkali saponification method, (2) solvent extraction method, (3) catalytic polymerization method, (4) high-temperature drying method, and (5) vacuum drying method. Generally, in order to improve the degreasing effect, two or more degreasing methods are often combined, but the actual application in production plants is not ideal. For example, the degreasing rate of pine wood treated by alkali saponification method is low, easy to discolor, and dull in luster. Under high-temperature conditions, especially under high-temperature alkaline conditions, the treated wood generally has a blackening phenomenon, which hinders the development of pine solid wood product production. SUMMARY

[0004] Therefore, the present application provides a wood degreasing process to solve the above technical problems.

[0005] A wood degreasing process, comprising the following steps:

[0006] STEP 101: providing a degreasing promoting liquid, the degreasing promoting liquid comprising sodium bicarbonate, sodium sulfate, and water, wherein the sodium bicarbonate accounts for 40-65 parts, the sodium sulfate accounts for 22-48 parts, and the rest is water, based on 100 parts;

[0007] STEP 102: pretreatment: soaking the wood in the degreasing promoting liquid for 0.5-3.5 hours, and maintaining the degreasing promoting liquid at 40-60°C and circulating flow;

[0008] STEP 103: heat treatment: taking the wood out of the degreasing promoting liquid, placing it in a carbonization kiln, and maintaining the temperature of the carbonization kiln at 80-140°C for 1-3 hours;

[0009] STEP 104: wood repair treatment: providing a curing agent, dissolving the curing agent in a solvent to form a repair agent solution, and then soaking the wood after the heat treatment into the repair agent solution, soaking at room temperature for 0.5-1.5 hours, the curing agent including aluminum chloride, calcium chloride, and water, the aluminum chloride accounting for 17-27 parts, the calcium chloride accounting for 35-65 parts, and the rest being water, based on 100 parts;

[0010] STEP 105: lumber drying treatment: providing a high-frequency vacuum drying machine and drying the modified wood to complete the degreasing of the wood.

[0011] Further, the pH value of the degreasing promoting liquid is maintained between 9 and 11.

[0012] Further, the degreasing promoting liquid is circulated under the action of a circulating pump to keep the temperature of the degreasing promoting liquid at 40-60°C.

[0013] Further, the degreasing promoting liquid includes sodium bicarbonate, sodium sulfate, and water, based on 100 parts, the sodium bicarbonate accounting for 48 parts, the sodium sulfate accounting for 32 parts, and the rest being water.

[0014] Further, in the pretreatment process, the wood is soaked in the degreasing promoting liquid for 1.5 hours, and the degreasing promoting liquid is stored in 55°C circulating water.

[0015] Further, the degreasing promoting liquid includes sodium bicarbonate, sodium sulfate, and water, based on 100 parts, the sodium bicarbonate accounting for 51 parts, the sodium sulfate accounting for 37 parts, and the rest being water.

[0016] Further, in the pretreatment process, the wood is soaked in the degreasing promoting liquid for 1.5 hours, and the degreasing promoting liquid is stored in 50°C circulating water.

[0017] Further, the degreasing promoting liquid includes sodium bicarbonate, sodium sulfate, and water, based on 100 parts, the sodium bicarbonate accounting for 42 parts, the sodium sulfate accounting for 37 parts, and the rest being water.

[0018] Further, in the pretreatment process, the wood is soaked in the degreasing promoting liquid for 2.5 hours, and the degreasing promoting liquid is stored in 60°C circulating water.

[0019] Compared with the prior art, the wood degreasing process provided by the application uses the degreasing promoting liquid and low-temperature weak alkaline solution in the early stage of degreasing, so that the resin in the wood is precipitated and subjected to esterification with the alkaline substance provided by the sodium bicarbonate, the purpose of removing the resin is achieved, and the sodium ions provided by the sodium bicarbonate and sodium sulfate can reduce the temperature of heat treatment and improve the speed of heat treatment, so that the heat treatment can be performed at medium temperature, the influence on the color and mechanical properties of the wood is reduced, and the stability of the product is improved. In addition, through the repair treatment process, a large amount of solution enters the inside of the wood, and then the pores and gaps in the wood are filled by generating calcium carbonate precipitates, so that the dimensional stability is improved and the mechanical properties of the wood are ensured, and then while ensuring the effective removal of the resin content in the wood and improving the gloss of the wood, the discoloration and blackening of the wood are avoided, and the quality of the subsequent wood products is improved. DETAILED DESCRIPTION

[0020] The specific embodiments of the application are further described below. It should be understood that the description of the embodiments of the application herein is not intended to limit the protection scope of the application.

[0021] A wood degreasing method, comprising the following steps:

[0022] STEP 101: providing a degreasing promoting liquid, the degreasing promoting liquid comprising sodium bicarbonate, sodium sulfate, and water, wherein the sodium bicarbonate accounts for 40-65 parts, the sodium sulfate accounts for 22-48 parts, and the rest is water, based on 100 parts;

[0023] STEP 102: pretreatment: soaking the wood in the degreasing promoting liquid for 0.5-3.5 hours, and maintaining the degreasing promoting liquid at 40-60°C and circulating flow;

[0024] STEP 103: heat treatment: taking the wood out of the degreasing promoting liquid, placing it in a carbonization kiln, and maintaining the temperature of the carbonization kiln at 80-140°C, and heat treating for 1-3 hours;

[0025] STEP 104: wood repair treatment: providing a solidifying agent, dissolving the solidifying agent in a solvent to form a repair agent solution, and then soaking the wood after heat treatment in the repair agent solution for 0.5-1.5 hours at room temperature, wherein the solidifying agent comprises aluminum chloride, calcium chloride, and water, wherein the aluminum chloride accounts for 17-27 parts, the calcium chloride accounts for 35-65 parts, and the rest is water, based on 100 parts;

[0026] STEP 105: lumber drying treatment: providing a high-frequency vacuum dryer, and drying the modified wood to complete the degreasing of the wood.

[0027] In the step 101, the main role of the sodium bicarbonate is to soften the resin and the fiber. Specifically, the alkaline substance provided by the sodium bicarbonate can react with the resin to decompose the resin. Before the wood is made into a wood product, the wood must be degreased. First, the density of the wood after degreasing is reduced, and it is not easy to deform before. Second, in order to enhance the adhesion of wood and glue, paint and coloring, otherwise the resin will slowly dissolve the paint on the surface of the wood during use, affecting the quality of the product. The content of the sodium bicarbonate should be limited to 40-65 parts. If the content is too low, the desired pH value cannot be reached. The pH value of the degreasing promoting liquid should be maintained between 9 and 11, that is, the pH value should be maintained in an alkaline environment. Because only in an alkaline environment can the resin be dissolved and precipitated to react with the resin to decompose the resin. If the pH value is too low, the resin cannot be precipitated, and the pH value cannot be higher than 11, because too strong alkaline can easily cause the wood to discolor. In addition, if the content of sodium bicarbonate is too low, it will also cause insufficient CO3 2- ions in the subsequent reaction. The sodium bicarbonate can provide a certain amount of CO3 2- ions and Ca 2+ react to form a precipitate that can fill the gaps in the wood, thereby improving the dimensional stability and flame retardant properties of the board. The sodium ions provided by the sodium bicarbonate are used to promote heat treatment, that is, to reduce the temperature during heat treatment and to improve the speed during heat treatment. However, sodium bicarbonate is alkaline and cannot be added in excess. If the pH is higher than 11, the wood will discolor. Therefore, in order to obtain sufficient sodium ions, the sodium sulfate needs to be added.

[0028] The sodium sulfate acts as a heat treatment promoter. Specifically, because the water-soluble sodium sulfate is slightly alkaline, it can supplement the alkalinity of the sodium bicarbonate, thereby improving the efficiency of heat treatment. Meanwhile, the sulfate ions remaining in the wood will react with the Ca 2+ in the stabilizer described below to form calcium sulfate precipitate, and with Al 3+ to form aluminum sulfate, which is a complex with certain viscosity that can improve the adhesion of the precipitate generated by other reactions inside the wood. The content of the sodium sulfate is limited to 22-48 parts. If the content is less than 22 parts, it cannot provide sufficient promotion effect, that is, it is difficult to achieve the purpose of supplementing the alkalinity of the promoting liquid. If the content is higher than 48 parts, the sodium sulfate will absorb water, causing other components to precipitate.

[0029] In STEP 102, the pretreatment method can be a conventional medium-temperature heat treatment method, i.e. the wood to be delignified is soaked in the delignification-promoting liquid. In the implementation, the pretreatment is performed in a special treatment pool. The treatment pool not only keeps the delignification-promoting liquid at 40-60°C, but also makes the delignification-promoting liquid flow in a circulation mode. The delignification-promoting liquid can flow in a circulation mode under the action of a circulating pump. Through circulation, the resin can be better dissolved, i.e. the problem that the delignification-promoting liquid around the wood cannot further react because the components of the delignification-promoting liquid have been completely reacted can be avoided. The delignification-promoting liquid is kept at a certain temperature, so that the sodium bicarbonate and sodium sulfate have a stable solubility, and the sodium bicarbonate and sodium sulfate are prevented from being precipitated and adhered to the surface of the wood when the temperature decreases, thereby affecting the quality of the wood. If the temperature is too high, too much water in the delignification-promoting liquid will evaporate, resulting in a decrease in the solvent, and thus the sodium bicarbonate and sodium sulfate are precipitated, thereby affecting the quality of the wood.

[0030] In STEP 103, it is known that cellulose or hemicellulose belongs to biomass material, which will generate lignin and other products after pyrolysis reaction, and carbonization occurs during heating, which helps to improve the stability of the wood. The carbonization treatment process itself is a prior art, but in the present application, by soaking in the delignification-promoting liquid, the influence of heat treatment on the mechanical properties of the wood can be reduced. Specifically, the industrial box-type heat treatment kiln is used for medium-temperature heat treatment of the wood, and the carbonization kiln is kept at 80-140°C. In the present embodiment, the temperature of the carbonization kiln is kept at 120°C. Keeping the temperature at 80-140°C can promote the resin to be discharged while achieving the purpose of heat treatment, and below 80°C has no treatment effect, and above 140°C will increase the loss of mechanical properties of the wood, i.e. the surface of the wood may become brittle.

[0031] In STEP 104, the curing agent is composed of aluminum chloride, calcium chloride, and water, and the aluminum chloride accounts for 17-27 parts, the calcium chloride accounts for 35-65 parts, and the rest is water, based on 100 parts. The aluminum chloride is a slightly acidic salt, which, in the early stage of use, neutralizes the alkaline substances remaining in the wood to maintain the acid-base balance in the wood, and Al 3+ reacts with CO3 2- ions to generate aluminum hydroxide precipitate attached to the inside of the wood, thereby improving the flame-retardant effect and dimensional stability of the wood. At the same time, Al 3+ can also react with the sulfate to generate aluminum sulfate, which is a gelatinous substance that can improve the adhesion of the precipitate, thereby preventing the precipitate from precipitating out of the wood. In addition, the aluminum chloride can also react with the residual resin to completely cure it in the wood, preventing the resin from precipitating out in the later stage and affecting the adhesion of the paint. The calcium chloride will separate out Ca 2+and the Ca 2+ ions in the solution can react with the CO3 2- ions remaining in the wood, and the precipitate can fill the pores of the wood fibers, thereby improving the dimensional stability and fire resistance of the wood. The content of the aluminum chloride should be limited to 17-27 parts, and too high a content can excessively react with the sulfate and CO3 2- ions, resulting in the inability to generate Ca 2+ precipitate, and too low a content can result in the inability to form sufficient effects.

[0032] The role of the calcium chloride is to add Ca 2+ to the solution to ensure sufficient precipitate formation to fill the pores formed by the soaking of the wood fibers, thereby improving the dimensional stability and fire resistance of the wood. The content of the calcium chloride should be limited to 35-65 parts, and too low a content cannot provide sufficient Ca 2+ , and too high a content can affect the Al 3+ reaction and cause resource waste.

[0033] In STEP 105, the high-frequency vacuum dryer is a conventional process and is not described in detail.

[0034] Experimental material: larch (500*100*40mm, moisture content 11.7%)

[0035] Example 1

[0036] STEP 101: Provide a degreasing accelerator solution including sodium bicarbonate, sodium sulfate, and water, with the sodium bicarbonate accounting for 48 parts, the sodium sulfate accounting for 32 parts, and the rest being water, based on 100 parts;

[0037] STEP 102: Pretreatment: Soak the wood in the degreasing accelerator solution for 1.5h, and maintain the degreasing accelerator solution at 55°C and in circulating flow;

[0038] STEP 103: Heat treatment: Take the wood out of the degreasing accelerator solution, place it in a carbonization kiln, and maintain the temperature of the carbonization kiln at 135°C for 2h of heat treatment;

[0039] STEP 104: Wood repair treatment: Provide a curing agent, dissolve 22 parts of aluminum chloride and 45 parts of calcium chloride in water to form a repair solution, and then soak the wood after the heat treatment in the repair solution for 1h at room temperature;

[0040] STEP 105: Drying of the finished product: Provide a high-frequency vacuum dryer, and dry the modified wood to complete the degreasing of the wood.

[0041] Example 2

[0042] STEP 101: providing a debinding promoting liquid, which includes sodium bicarbonate, sodium sulfate, and water, wherein the sodium bicarbonate accounts for 51 parts, the sodium sulfate accounts for 37 parts, and the rest is water, in 100 parts;

[0043] STEP 102: pretreatment: soaking the wood in the debinding promoting liquid for 1.5 h, and maintaining the debinding promoting liquid at 50°C and circulating flow;

[0044] STEP 103: heat treatment: taking the wood out of the debinding promoting liquid, placing it into a carbonization kiln, and maintaining the temperature of the carbonization kiln at 130°C, and heat treating for 1.5 h;

[0045] STEP 104: wood repairing treatment: providing a curing agent, dissolving 20 parts of aluminum chloride and 55 parts of calcium chloride in water to form a repairing agent solution, and then soaking the wood after the heat treatment into the repairing agent solution for 1 h at room temperature;

[0046] STEP 105: lumber drying treatment: providing a high-frequency vacuum drying machine, and drying the wood after the modification treatment to complete the debinding of the wood.

[0047] Example 3

[0048] STEP 101: providing a debinding promoting liquid, which includes sodium bicarbonate, sodium sulfate, and water, wherein the sodium bicarbonate accounts for 42 parts, the sodium sulfate accounts for 37 parts, and the rest is water, in 100 parts;

[0049] STEP 102: pretreatment: soaking the wood in the debinding promoting liquid for 2.5 h, and maintaining the debinding promoting liquid at 60°C and circulating flow;

[0050] STEP 103: heat treatment: taking the wood out of the debinding promoting liquid, placing it into a carbonization kiln, and maintaining the temperature of the carbonization kiln at 140°C, and heat treating for 1 h;

[0051] STEP 104: wood repairing treatment: providing a curing agent, dissolving 18 parts of aluminum chloride and 50 parts of calcium chloride in water to form a repairing agent solution, and then soaking the wood after the heat treatment into the repairing agent solution for 1.5 h at room temperature;

[0052] STEP 105: lumber drying treatment: providing a high-frequency vacuum drying machine, and drying the wood after the modification treatment to complete the debinding of the wood.

[0053] Detection method: the bending strength and the compression strength along the grain are detected according to GB / T 1936.1-2021 Wood - Determination of modulus of rupture and GB / T 1935-2021 Wood - Determination of compression parallel to the grain, and the paint film adhesion is detected according to the relevant method in 4.57 of GB / T 17657-2022 Wood-based panels and veneered wood-based panels - Determination of physical and mechanical properties.

[0054] Test results

[0055] Compressive strength parallel to the grain / MPa Bending strength / MPa Paint film adhesion Example 1 51.31 72.54 6 Example 2 53.48 74.82 6 Example 3 52.32 73.43 6 Control 55.82 75.63 3

[0056] Examples 1-3 are larch wood treated by the degreasing process, and the control group is untreated larch wood.

[0057] From the data in the table, compared with the control group, the mechanical properties of the larch after degreasing treatment in examples 1-3 decrease less, and the paint film adhesion increases more, thereby proving that the mechanical properties of the wood treated by the degreasing process do not have great loss, and the practical performance of the adhesion is greatly improved.

[0058] Compared with the prior art, the wood degreasing process provided by the present application uses the degreasing promoting liquid in the early stage of degreasing and adopts a low-temperature weak alkaline solution, which can make the resin precipitate from the wood and undergo lipolysis decomposition reaction with the alkaline substance provided by the sodium bicarbonate, achieve the purpose of dissolving and removing the resin, and through the sodium bicarbonate and sodium sulfate, both of which are alkaline substances, the acidic substances generated inside the wood during the heat treatment process can be neutralized to protect the wood fibers from being destroyed by pyrolysis during subsequent heat treatment, thereby improving the physical and mechanical properties of the wood. In addition, through the repair treatment process, a large amount of solution enters the inside of the wood, and then through the generation of calcium carbonate and aluminum hydroxide precipitates, the pores and voids inside the wood are filled, thereby improving the dimensional stability and ensuring the mechanical properties of the wood, and further ensuring the effective removal of the resin content in the wood, improving the gloss of the wood, and avoiding discoloration and blackening of the wood, thereby improving the quality of the subsequent wood products.

[0059] The above is only a preferred embodiment of the present application, and is not used to limit the protection scope of the present application, any modification, equivalent replacement or improvement within the spirit of the present application is covered within the scope of the claims of the present application.

Claims

1. A wood degreasing process comprising the steps of: STEP 101: providing a degreasing promoting liquid comprising sodium bicarbonate, sodium sulfate, and water, wherein the sodium bicarbonate accounts for 40-65 parts, the sodium sulfate accounts for 22-48 parts, and the rest is water, based on 100 parts, and the sodium bicarbonate is contained in an amount to maintain the pH of the degreasing promoting liquid between 9 and 11 to precipitate resins in wood; STEP 102: pretreatment: soaking wood in the degreasing promoting liquid for 0.5-3.5 hours, and maintaining the degreasing promoting liquid at 40-60°C and circulating the degreasing promoting liquid; STEP 103: heat treatment: taking the wood out of the degreasing promoting liquid, placing the wood in a carbonization kiln, and maintaining the temperature of the carbonization kiln at 80-140°C for 1-3 hours; STEP 104: wood repair treatment: providing a curing agent, dissolving the curing agent in a solvent to form a repair agent solution, and then soaking the wood after heat treatment into the repair agent solution, soaking at room temperature for 0.5-1.5 hours, the curing agent including aluminum chloride, calcium chloride, and water, the aluminum chloride accounting for 17-27 parts, the calcium chloride accounting for 35-65 parts, and the rest being water, the Al 3+ ions in the aluminum chloride react with the CO3 2- ions remaining in the wood to form precipitates that fill the pores of the wood fibers, thereby improving the flame retardant effect and dimensional stability of the wood. 3+ The aluminum sulfate generated by the reaction with sulfate ions improves the adhesion of the precipitate, the aluminum chloride reacts with the residual resin to completely cure it inside the wood, preventing the precipitation of the resin in the later stage and affecting the use effect of the wood, and the Ca 2+ ions separated from the calcium chloride react with the CO3 2- ions remaining in the wood to form precipitates that fill the pores of the wood fibers, thereby improving the flame retardant effect and dimensional stability of the wood. 2+ ions separated from the calcium chloride react with the CO3 2- ions remaining in the wood to form precipitates that fill the pores of the wood fibers, thereby improving the flame retardant effect and dimensional stability of the wood. STEP 105: drying treatment of the lumber: providing a high-frequency vacuum dryer, and drying the wood after the repair treatment to complete the degreasing of the wood.

2. The wood degreasing process of claim 1, wherein: The degreasing promoting liquid is circulated by a circulating pump to maintain the temperature of the degreasing promoting liquid at 40-60°C.

3. The wood degreasing process of claim 1, wherein: The degreasing promoting liquid comprises sodium bicarbonate, sodium sulfate, and water, wherein the sodium bicarbonate accounts for 48 parts, the sodium sulfate accounts for 32 parts, and the rest is water, based on 100 parts.

4. The wood degreasing process of claim 3, wherein: In the pretreatment process, the wood is soaked in the degreasing promoting liquid for 1.5 hours, and the degreasing promoting liquid is stored in 55°C circulating water.

5. The wood degreasing process of claim 1, wherein: The degreasing promoting liquid comprises sodium bicarbonate, sodium sulfate, and water, wherein the sodium bicarbonate accounts for 51 parts, the sodium sulfate accounts for 37 parts, and the rest is water, based on 100 parts.

6. The wood degreasing process of claim 5, wherein: In the pretreatment process, the wood is soaked in the degreasing promoting liquid for 1.5 hours, and the degreasing promoting liquid is stored in 50°C circulating water.

7. The wood degreasing process of claim 1, wherein: The degreasing promoting liquid comprises sodium bicarbonate, sodium sulfate, and water, wherein the sodium bicarbonate accounts for 42 parts, the sodium sulfate accounts for 37 parts, and the rest is water, based on 100 parts.

8. The wood degreasing process of claim 7, wherein: In the pretreatment process, the wood is soaked in the degreasing promoting liquid for 2.5 hours, and the degreasing promoting liquid is stored in 60°C circulating water.