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Waterborne coatings are coming, how to prepare the technology

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"Water-based paint production enterprises have been fighting for a decade, and now it's time to shine." Zhu Yanan, Secretary-General of China Waterborne Wood Coatings Technology Alliance, said in an interview with China Chemical News recently. The new environmental protection policy is becoming more and more stringent, consumers' health awareness is increasing, and high VOCs coatings seem to be exhausted. But according to the reporter of China Chemical Industry News, in wood coatings, the proportion of water-based is far below 10%. In addition to the low acceptance of downstream companies, the main reason is that the application cost and product performance of water-based coatings are still not satisfactory. In the face of the coming water-based era, what new requirements are put forward for supporting resins, coloring systems, additives, etc.? How should raw material manufacturers respond? A reporter from China Chemical Industry News conducted an extensive interview.

Resin R & D should be a system

Yang Huan, market service manager of Wanhua Chemical Group Co., Ltd., believes that the further oil-to-water conversion of wood paints mainly faces the following technical challenges: firstly, the hardness of the paint film is insufficient, secondly, it is difficult to achieve a fully enclosed effect, and thirdly, the problem of wood bulging Fourth, the drying process is greatly affected by the environment. The reporter from China Chemical Industry News learned that most of the performance of the coating is achieved by resin. The key to water-based wood coatings depends on the performance and cost of water-based resins.

Yang Huan pointed out that different fields of furniture use have different requirements on coating performance. For example, outdoor furniture requires water-resistant and water-white paint, and high requirements for weather resistance and flexibility; indoor furniture requires high hardness, appearance, chemical resistance, and mechanical properties. This requires the targeted selection of different resin systems into the formulation design. From the resin point of view, there are many classifications of oil-based paint resins, such as nitro paint, PU paint, UV paint and so on. Most of the resins used in wood coatings before were acrylic emulsions. Although the cost is low, the drying is fast, and the sandability is good, but the performance is single, it is difficult to compare with the above oily coatings. Therefore, more water-based resin systems are needed to form the overall effect to replace oily. Resin. How to improve the performance, how to reduce the sensitivity of the paint film to the environment during the drying process, how to solve the bulge problem, and how to improve the wettability of the water-based resin to the wood have to be solved by the resin supplier. The PUD, PUA, waterborne UV, and waterborne two-component systems that have been successfully developed have given downstream users more options.

Hua Dongshuan, deputy general manager of Hebei Chenyang Industry and Trade Group Co., Ltd., said in an interview that the development of new chemical materials is changing rapidly, which provides a strong guarantee for the optimization of the performance of water-based coatings. At present, water-based resins of multinational companies such as Opel Di and DSM are used more frequently in China. The water-based resin products produced by domestic enterprises have room for improvement in the stability of performance indicators. "For example, temperature control is critical in emulsion production. If the temperature control equipment is not sensitive, there will be a wide range of temperature fluctuations, resulting in performance differences between batches that are outside the allowable error. Domestic companies are in the detection of finished products, production control There is still a big gap in terms of means compared with international manufacturers. At present, some enterprises are introducing foreign production equipment and implementing fully automated control. Only when the equipment is highly automated and the control is precise, can product performance indicators be stable, and downstream companies In order to produce a stable product." Hua Dongshuan said.

The coloring system needs water permeability

Due to different solvents, the requirements of water-based paints on coloring systems are quite different from those of oil-based paints, which has spawned the development of water-based coloring systems.

According to Shu Han, a technical engineer of Dongguan Caizhihong Chemical Co., Ltd., color concentrate is a coloring scheme for transparent colors in the paint industry and plays an increasingly important role in the application of water-based paints. A good water-based color concentrate not only needs to have good compatibility with water-based coatings, but also the toner used must have good fire resistance, temperature resistance, color migration resistance and sufficient vividness, and it has a solvent-based performance All the characteristics of the product can be better accepted by users.

At present, the transparent coloring system used in the water-based system on the market mainly includes two systems of acid dyes and metal complex color concentrates. Acid dyes can easily react with weakly alkaline water-based paints and can easily fade. The previous metal complex chromogen requires the dissolution of organic solvents, and the cost is relatively high. In order to adapt to the application of water-based coatings, Caizhihong has developed a series of coloring products such as CH-W121 water-based yellow essence, CH-W721 water-based brown essence, CH-W823 water-based black essence, and CH-223 water-based orange essence. The metal complex pigments in these aqueous color concentrates are not in a state of complete compatibility in an aqueous system, but a stable dispersion state.

Industry experts point out that color paste is also a large category of products in water-based paint coloring systems. With the water-based coatings, there is a lot of room for future development of colorants that can be used with water-based coatings. Water-based transparent colorants are mainly used for wood coloring and topcoats for higher-end cars. After using transparent color paste, Wood Grace can show the wood grain well and improve the wood grade. The use of transparent color paste in combination with aluminum silver paste and pearlescent pigments in automotive coatings can improve the effect of automotive coatings. The water-based solid color paste is widely used in water-based industrial paint coloring systems, and its performance is greatly related to the light resistance, weather resistance and chemical resistance of the pigment itself.

With the increasing amount of water-based coatings in the future, the water-based coloring system will also become more and more mature, which can provide more personalized solutions for downstream users.

Additives need new recruits

It is understood that the main difference between water-based paints and oil-based paints is the solvent. The film formation, flow and leveling of the paint, and the performance of the paint film are closely related to the solvent. There are many types of oil-based paint solvents, and the solvent can be adjusted according to needs. However, water-based paints have only water and a small amount of coexisting solvents. It is difficult to achieve the film-forming, flow and leveling properties of oil-based paints, and additives are needed to adjust.

The reporter learned from interviews that, theoretically, water-based emulsions can obtain better physicochemical properties than oily systems due to their higher molecular weight. However, since the raw materials of the oily system have been fully developed, technical R&D personnel can obtain ultra-high-performance coatings through the selection of special raw materials or additives. In contrast, water-based products are not very rich, and there are no emulsions with superior performance to choose from. It is very important to use the film-forming additives correctly and match the additives of the appropriate system to improve the performance of the paint film.

It is foreseeable that as the oil-to-water process accelerates, a number of new film-forming auxiliaries, rheology auxiliaries, leveling agents, cross-linking agents, and functional fillers suitable for water-based coatings will emerge.

In addition, because the waterborne wood coating formulation contains a large amount of organic substances, it is very suitable for the growth of microorganisms. Microbial mucus will decompose the ingredients in the wood coating, affecting the product's fluidity and other properties, causing the product to deteriorate and affect its use. Therefore, it is very necessary to control the growth of microorganisms. The preservatives in the tank need to have the following characteristics: broad-spectrum antibacterial, wide pH application range, meeting protection requirements under process conditions, safe operation, good compatibility, low addition, and complying with relevant regulations .

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