Wood preservation is a technique that protects wood from erosion by organisms such as insects and bacteria. One of the wood processing technologies is widely used for the protection of rods, square materials and plates to prolong the service life of wood and reduce the consumption of wood. The main method of international wood preservative treatment is to use an aqueous preservative that is not suitable for dissolving, and apply wood preservatives into wood fibers while applying pressure to the wood in a closed vacuum tank. After pressure-treated wood, the stability is stronger, and the wood preservative pavilion can effectively prevent molds, termites and insects from invading the wood. As a result, the treated wood has excellent anti-corrosion properties for long-term use under harsh outdoor conditions. Let me explain the relevant knowledge of wood preservation .

Why use wood preservatives

Wood is a natural organic material with obvious biological characteristics and is easily attacked by bacteria, insects, marine borers and other organisms. Before use, according to different application environments, using suitable preservatives and proper treatment can effectively delay the decay of wood. With the improvement of people's living standards, the demand for wood is also increasing. The forest resources that can be used for harvesting in our country are very limited. It is also unrealistic to hope that the use of large amounts of foreign exchange for timber imports. Based on the domestic, making full use of existing resources and taking the road of sustainable development is the only way for the development of China's timber industry. The preservation of wood and the extension of the service life of wood products are one of the important ways to save wood and protect forest resources. There are few woods used in China after antiseptic treatment, and most of them use traditional wood preservatives that are harmful to humans and the environment. Therefore, understanding the progress of wood preservatives and developing and developing new types of wood preservatives are very necessary.

Characteristics of wood preservatives

(1) High toxic effects: The effectiveness of wood preservatives is mainly determined by their toxicity to harmful organisms. The greater the biological toxicity that harms wood, the stronger its anti-corrosion effect. In general, other additives are added to the wood. The first is the anti-corrosion effect and can enhance the rigidity, strength and durability of the wood.

(2) Persistence and stability: The wood preservative should have relatively stable chemical properties. After it is injected into the wood, it will not easily evaporate, it will not be lost easily, and it will maintain its due toxicity for a long time.

(3) Strong penetration: Wood preservatives must penetrate easily into the wood and have a certain depth of investment.

(4) High safety: Wood preservatives should be highly toxic to various kinds of helminths that harm wood, but at the same time it should be low or non-toxic to humans and animals, and it should not cause pollution or damage to the environment. With people's concern for the environment and sustainable development, high-efficiency and environmental-friendly compound wood preservatives have received due attention, such as ISU30 and ISU40 from Shanghai Oumo.

(5) Low corrosiveness: Preservatives are less corrosive to various metals and ideal for neutrality.

(6) Small damage to wood: After the wood has been treated for preservation, it is appropriate for the mechanical strength, good texture and pleasant color of wood not to affect its use.

(7) Low price and wide supply: In order to promote the development of wood preservative industry, wood preservatives must have sufficient sources of supply, and raw materials have low prices and are competitive.

Classification of wood preservatives

(1) Water-borne (water-soluble) preservatives: They are wood preservatives that are soluble in water and have water as their carrier. Such as CCA, ACQ, CA-B, CB-A, ACZA, ACC, CC and so on.

(b) Organic solvents (oil-borne, oil-soluble) preservatives: A wood preservative that contains pesticides, fungicides, or both, and is dissolved in organic solvents. For example, pentachlorophenol, chlorothalonil, copper naphthenate, etc., copper quinolinate.

(3) Oil preservatives: antiseptic oil, coal tar, and oyster sauce.

  

Wood preservation method

Wood preservative treatment is the use of processing equipment and appropriate treatment processes (or methods) to inject wood preservatives into the interior of the wood, so that the preservatives are evenly distributed and fixed in the wood, forming insoluble in water, a certain degree of bacteria and insects The toxic or resistant protective layer plays a role in preventing bacteria and insects. In theory, the entire interior of the wood is infiltrated with preservatives, and its content reaches the inhibitory concentration of the worms, which is ideal. A large number of tests have shown that the main indicators for measuring the quality of wood preservative treatment are the drug loading and penetration of preservatives.

Wood pressurization treatment uses a large pressure difference between inside and outside the wood, usually infiltrating the preservative into the deeper interior of the wood, distributing it evenly, ensuring the quality of the antiseptic treatment, and its products are widely used. Non-pressure treatment, due to low drug loading of preservatives, light penetration, suitable for the temporary storage of timber and the treatment of special rigid materials (such as veneer, wood chips). In addition, during the pressurization process, the antiseptic solution is in a closed system and is not exposed to the atmosphere, and has little effect on workers and the surrounding environment. Therefore, the anticorrosive treatment currently used in the industry requires pressure treatment.

Immersion method

Under normal temperature and pressure, the wood is soaked in the tank or pool containing the preservative solution, and the wood is always in the liquid surface. The soaking time depends on species, wood specifications, moisture content, and type of agent, in order to achieve the required drug retention and penetration. In order to improve the treatment effect, ultrasonic waves, heating devices, and surfactants may be added to the soaking solution to improve the permeability of the wood. Depending on the length of the soaking time, the soaking method can be instantaneously immersed (times from seconds to minutes), short-term soaks (minutes to hours), and long-term soaks (hours to 1 month). Suitable for veneer and remedial corrosion treatment, and temporary wood storage treatment. Http://

Diffusion method

According to the principle of molecular diffusion, moisture in wood is used as a carrier for drug diffusion, and the drug diffuses from a high concentration to a low concentration and diffuses into the deep layer of wood. For this, the proliferation of preservative-treated wood must meet the following conditions: 1 The moisture content of the small material is sufficiently high, usually 35% to 40% or more, and the raw material is the best; 2 The water-borne agent (diffusion type) has high solubility and is cured. Slow; 3 high ambient temperature and humidity. According to the operation process, the diffusion method can be divided into paste expansion method, dipping or spray diffusion method, band diffusion method, drilling diffusion method (or droplet diffusion method) and two-agent diffusion method. Diffusion process equipment investment less production process is simple. Easy application and promotion in the vast rural areas. Similar to this method is the sap replacement method.

  

Hot and cold trough

Using the principle of thermal expansion and contraction, the gas in the wood expands and shrinks, resulting in a pressure difference, so as to overcome the liquid's resistance to penetration, that is, the wood is heated in a hot liquid. The air in the small wood expands, part of the water evaporates, the pressure inside the wood is higher than the atmospheric pressure, and the air and water vapor overflow to the outside. At this time, the wood is rapidly placed in a cold liquid, the wood is quenched, and the air in the wood is Negative pressure due to shrinkage, cold liquid penetrates into the wood. According to the treatment method and the configuration of the cold trough, it can be divided into double trough alternate method, single trough hot/cold liquid alternating method and single trough cooling method. Due to the low processing efficiency (compared with the pressurization method), the energy consumption per unit product is large. Commonly used for small quantities of wood preservation.

Editor's summary: So far, the most commonly used method to prevent wood decay is to use chemical agents for preservation. The most commonly used is water-soluble preservatives, accounting for about 3/4 of the total amount of preservatives used. In order to extend the useful life of wood, we can use wood preservatives in an appropriate amount, which is also to save wood and protect forest resources.

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