What is a wood preservative?

Drugs made of single or multiple compounds have toxic or inhibitory effects on organisms that harm wood and can protect wood for a long time. As a wood preservative, it should meet the following main conditions: ① strong toxicity. It has lasting toxicity or inhibitory effect on microorganisms (mainly basidiomycetes) and pests that harm wood. 2 insist. Preservatives treated in wood are not easy to lose water and are not easy to be affected by atmospheric factors. The agent itself should be relatively stable, and when it comes into contact with other materials, it will not cause the quality of the treated wood and have adverse effects. ③ Safe use. Both drugs and treated wood are harmless to people and warm-blooded animals, and will not pollute the environment during production and use, and the treated wood will not emit harmful gases when burning. ④ Economical and practical. The amount of preservatives in wood per unit volume is large, so the cost is low. Although it is difficult to meet the above conditions completely, the wood preservatives currently used have developed into single or multifunctional agents, such as wood mildew-proof and discoloration-proof agents, wood insecticides, flame retardants, decorative preservatives, hydrophobic preservatives and so on. And continue to develop more perfect high-quality preservatives.

In the folk, people have long noticed the use of chemicals to prevent the corruption of wood and bamboo. For example, ancient people used natural resin, tar, natural asphalt, animal and vegetable oil or salt to treat wood and bamboo. However, the application of wood preservatives as commodities in production began in the18th century. With the development of production and the increase of wood consumption, the varieties of wood preservatives have also developed greatly, forming a branch drug different from pesticides. Since 1980s, many chemicals have been patented as wood preservatives every year. According to incomplete statistics, there are hundreds of preservatives sold as commodities all over the world. In addition to some main agents, bactericides, insecticides, flame retardants, waterproofing agents and various additives are often added to these commercial agents, so that wood preservatives have multiple functions and improve the quality of wood protection.

Wood preservatives can be roughly divided into three categories: ① Tar. The most commonly used is coal tar creosote. Also known as wood preservative oil. In use, a certain amount of coal tar or petroleum heavy oil is often mixed. In order to further improve the performance of anticorrosive oil, a small amount of pentachlorophenol, arsenic, sulfur or pesticides are added. ② Oily (soluble) type. It is a compound soluble in organic solvents. Commonly used are pentachlorophenol, copper naphthenate, copper 8- hydroxyquinoline, organic tin salt and organic iodized salt. Since the late 1970s, some organic fungicides and insecticides have been developed and applied to wood protection. ③ water solubility. In the early days, single inorganic salts were used as wood preservatives, such as zinc chloride, sodium fluoride and copper sulfate. In order to improve the performance, compound anticorrosive agents are used, such as copper-chromium-arsenic, copper-chromium-boron, copper-chromium-fluorine, fluorine-chromium-arsenic phenol, copper-ammonium arsenate and acidic copper chromate. There are many brands of such preservatives, among which copper, chromium and arsenic are one of the most widely used preservatives in the world. In addition, the aqueous emulsions of ammonia-soluble pentachlorophenol, pentachlorophenol and naphthenate were developed in 1970s and 1980s, which were mainly used to save organic solvents and facilitate the fixation of chemicals in wood. For convenience, some preservatives are also made into concentrated solution, ointment, dispersant, suppository or paint. As a special purpose, there are also gas preservatives.

Any effective wood preservative must first determine its toxicity, that is, the preservative content per unit volume of wood; The initial toxicity value that can prevent bacteria, insects or termites from invading is also called the initial dose value. It is an important quality index of preservatives, which can be obtained through laboratory and field experiments. In addition, there are various performance tests.