Because of its beautiful texture and color, easy processing, high strength to weight ratio, adjustable indoor temperature and humidity characteristics, wood is widely used in indoor and outdoor decoration, furniture and architecture。However, wood itself is a biological material, vulnerable to fungi, bacteria, insects and other biological damage and degradation, thus affecting its use quality and service life。Through certain physical and chemical means, wood anticorrosion treatment can slow down or prevent the occurrence of biological degradation, thereby extending the service life and reducing the waste of wood resources, which is an effective means of saving and efficient use of wood resources。

Wood after anti-corrosion treatment can generally extend the service life of 5 to 10 times。According to China's current annual demand for commercial wood 1.500 million m³ calculation, if the proportion of wood preservation from the current 3% to 10%, at least 40 million m³ more wood can be saved every year, accounting for about a quarter of China's current annual demand for commercial wood。

It can be seen that wood preservative treatment, as a "throttling" measure of insufficient wood resources in our country, has great practical significance and strategic value for protecting forest resources, realizing sustainable utilization of wood, and ensuring national wood security。

Discard the first generation: protecting health and the environment

China's wood preservative industry started from the anticorrosion of railway ties, and mainly used coal creosote, coal tar and other oil preservatives at the beginning。Since 2000, with the transformation of preservative wood from industry to civil market, water-borne preservatives represented by chromated copper arsenate (CCA) have gradually become the most commonly used wood preservatives in China's market。

Although CCA preservatives have the advantages of excellent anti-corrosion performance and low price, such preservatives contain carcinogenic chemicals such as chromium, arsenic and other heavy metal salts, which may harm human health and environmental quality in the process of preservative production, wood preservative treatment and use of preservative materials。At the same time, CCA anti-corrosion treatment materials lack of effective treatment ways after waste。Therefore, the United States, Europe, Japan and other countries and regions have banned or restricted the use of CCA treated materials。

However, China's anticorrosive wood market is still dominated by CCA preservatives at this stage, and the development of related technologies is still lagging behind. How to realize the green development of China's anticorrosive wood industry through technical optimization and upgrading is an urgent problem to be solved。

Improved second generation: Improved resistance to loss

At this stage, the new generation of wood preservatives used in the market to replace CCA preservatives are mainly ammonia dissolved quaternary amine copper (ACQ) and cuprizole (CA), whose main components are copper and organic biocides, and do not contain heavy metals such as chromium and arsenic。However, it is precisely because of the lack of such heavy metal elements, ACQ and CA in the wood fixation ability is poor, in contact with water or soil conditions are prone to loss, resulting in a certain degree of pollution to soil or water, while affecting the anti-corrosion effect of treated materials。

In response to this problem, the team of Professor Cao Jinzhen of Beijing Forestry University invented a universal method to accelerate copper fixation in wood such as hot water post-treatment, microwave post-treatment, hot air/steam drying post-treatment, and developed a new process to enhance the effect of waterproofing agent on copper based preservatives。This series of methods improve the production efficiency, reduce the loss rate of copper based preservatives, extend the service life of anti-corrosion treatment materials, reduce the adverse impact of anti-corrosion treatment materials on the environment, and provide a new direction for the promotion of new copper based preservatives。

Another type of environmentally friendly wood preservatives - boron preservatives, due to its easy loss, can only be used in indoor environments。Professor Cao Jinzhen's team developed a composite preservative treatment process of inorganic borate and quaternary ammonium salt using a two-step process to treat wood，Quaternary ammonium borate synthesized in situ in wood can achieve fixation through cation exchange with hydroxyl and carboxyl groups in cellulose and lignin，The water loss resistance of this borate was significantly improved，Boron loss can be reduced from close to 100% to 10%。This technology expands the scope of use of boron-based wood preservatives, provides technical support for boron-based wood preservatives to replace traditional copper preservatives and further improve the environmental protection of wood preservatives。

Development of the third generation: stable long-term, green environmental protection

In recent years, the US market has begun to use the third generation of environmentally friendly water-borne organic preservatives without metal components (Ecolife series products), and has been widely recognized by the market。However, this kind of preservatives have strong technical barriers, how to choose the right organic preservatives and choose the right additives to make water-borne products need to explore。

After a period of technical research，Professor Cao Jinzhen's team invented a low toxicity, high efficiency isothiazolinone organic preservative microemulsion，Free of toxic organic solvents and metal components，Environmentally friendly，The average particle size is about 40nm，It has excellent dilution stability, storage stability, centrifugal stability and thermal stability，It is highly permeable to wood and the preparation process is simple and safe。The microemulsion water-borne organic preservative has excellent resistance to water loss, and the treatment concentration is 0.10% can effectively prevent the growth of decay bacteria。In addition, unlike copper-containing preservatives, such preservatives do not change the apparent color of the wood after use, which can better retain the natural texture of the wood。The technology has been promoted in cooperation with related enterprises, and can be used in many fields such as solid wood balconies, restructured bamboo, and wooden pallets。

The research and development and promotion of environment-friendly microemulsion water-borne organic preservatives have expanded the types of existing wood preservatives, made up for the gap of related products in China, and promoted the development process of wood preservatives green。