Development of environmentally friendly water-based paint for steel drum
Text / Liu Shengbo
[Editor's note] At the China Packaging Technology Association's "2017 Science and Technology Awards" review meeting, Hubei Jiaji Synthetic Materials Co., Ltd. project "Development of environmentally friendly water-based coatings for steel drums" won the third prize, which is also 2017 Received the only award related to the steel industry in the China-Bridge Science and Technology Award.
I. Understand the needs of the steel drum industry and establish a development project
Since the first voluntary volatile organic compound (VOC) law was enacted in California in 1966, countries have increased the control of VOC emissions and the production and use of high VOC coating products. Due to its extremely low VOC and energy saving, it has become the mainstream of the modern coatings industry. The main types of waterborne coatings: waterborne polyester, waterborne acrylic, waterborne polyurethane coatings. Water-based paints are currently developing environmentally-friendly paints, but they are used in Asia at a very low rate of only 3% (42% in Europe). In the field of water-based paints, there is still a big gap between China and developed countries. The reasons for the slow development of water in the past are mainly two aspects: First, the performance of water-based coatings cannot reach solvent-based products; second, the investment in water-based coatings is high in production and use, such as drying rooms, strong cooling equipment, and production sites. Temperature and humidity control adjustment equipment, etc.
Amino polyester coatings have long been used in automotive coatings, industrial coatings, coiled iron coatings, etc. due to their excellent flexibility and high processability. Waterborne polyesters not only inherit oily polyesters. The advantages, even in some properties beyond solvent-based products. In recent years, the price of crude oil has risen sharply, resulting in the continuous increase in the price of solvent-based coatings, and some even higher than the price of water-based coatings. This situation has also promoted the development of water-based coatings from the side, making some places Water-based coatings have an exciting and prosperous situation, which is a rare opportunity for the development of waterborne coatings.
In recent years, the degree of water-based automotive coatings has increased rapidly, especially in the original automotive paints, such as Audi, Mercedes-Benz, Honda, Toyota, Nissan, Hyundai and other well-known brands have professional water-based automotive coating lines. Mainly concentrated in automotive primer, intermediate coating, base paint gradually changed to water-based paint, for various reasons, the varnish is still dominated by solvent type. The transformation of automotive paint to water-based can not only reach the environmentally-restricted emission index, meet the low-carbon concept, reduce VOC emissions, etc., but also affirm and promote the water-based road of the paint industry.
Aqueous saturated polyester resin is widely used in automotive coatings, metal base paints, top coats and other multi-coatings due to its excellent properties.
In steel drum manufacturing companies, solvent-based amino lacquers are widely used, and high-temperature baking processes are commonly used. In the paint category and curing method, it is consistent with automotive coatings, but there are differences in specific indicators. Therefore, we chose to use water-soluble polyester resin with water-soluble amino resin to make water-based steel drum coating. This is mainly to consider the following five points:
1. The polyester amino system is used, the quality of the coating film is guaranteed, and it can meet the anti-corrosion and decorative performance requirements of the steel drum;
2, the use of polyester amino system, the barrel factory basically does not need new equipment, no additional investment is required;
3, the spraying process does not change, the painter is easy to master, and the quality is well controlled;
4. The operating cost is equivalent to that when using oily paint;
5. The comprehensive cost of paint is basically the same as that of oil paint. Steel drum enterprises can accept it.
Second, study the characteristics of the steel barrel industry and determine the direction of development
1. Problems to be solved in the application of steel drum industry
In fact, the research and application of water-based steel drum coatings in China are relatively early. Since 2008, there have been attempts by domestic coating companies to apply waterborne amino coatings to the steel drum industry, and have achieved certain results. After several years of application and adjustment, the quality of water-based steel drum coatings has been continuously improved. Currently, the performance of water-based paints is comparable to that of solvent-based paints. Some indicators are even better.
However, the special nature of the steel drum coating process has caused many water-based paint manufacturers to lose in field applications.
Throughout the development history of water-based steel drum coatings, it is possible to clearly find the problems that need to be solved in water-based steel drum coatings:
1) Construction properties of water-based steel drum coating (water-based color coating)
2) VOC content of waterborne steel drum coating
3) Shelf life of water-based steel drum coating
Our scientific and technological innovation work is carried out around the above three issues.
2. Establishment of key research directions
Specifically, the development of our water-based steel drum coating is divided into two parts:
1) Synthesis of aqueous polyester resin;
In the design of waterborne polyester resin synthesis, we focus on improving the storage stability of waterborne polyester resin in addition to the physical and chemical properties of the resin. Through practical application, our company's water-based steel drum coating can guarantee the shelf life of 12 months, while the shelf life of other manufacturers' water-based steel drum coatings is up to 6 months and short is only 3 months.
2) Development of water-based steel drum coating (color coating).
In the water-based paint color barrel process, there are two main problems to be solved:
a. Wet-on-wet construction process, it is easy to produce two colors of bleed and paint fog at the color separation and trimming;
b. Water-based paint is easy to sag: For bleed and splash, we have solved this problem by adding micro-incompatible state in the two-layer wet film by adding homemade auxiliaries. For sagging, we have adjusted the body structure and linear structure types and proportions of water-based polyester resin, and supplemented with high-efficiency anti-sagging additives, which solved this problem well.
3. Six patents produced in the development
Throughout the R&D process, we focused on objective reality and strived for perfection of products. At the same time, we did not forget the protection of intellectual property rights. During the period, we filed and authorized 6 practical patents, namely:
1) an aqueous resin synthesis condenser;
2) A horizontal sander that is easy to clean and temperature-adjustable;
3) A vertical sand mill;
4) a paint adjusting device;
5) a high speed disperser;
6) An insulative storage device for aqueous resin.
Third, breakthroughs in key issues of technological innovation
Our scientific and technological innovation work is to break through the above three key issues.
1. VOC content of waterborne steel drum coating
The state promotes environmental protection and actively promotes water-based paints, which is to reduce VOCs in paint products. However, many manufacturers' water-based steel drum coatings have a VOC of 200 g/L or more. Although individual manufacturers can achieve 150 g/L, such VOC content is still high and does not meet the HJ2537-2014 environmental labeling product. The technical requirements for waterborne coatings shall not exceed VOC requirements of 80 g/L.
The reason is mainly because many manufacturers are purchased or synthesized water-soluble polyester resins. Since the water-soluble polyester resin contains about 30% of organic solvents, the VOC content of the produced water-based steel drum coatings is high.
We synthesize polyester water solution by special process. The content of organic solvent in this water solution is less than 5%, so the VOC of the water-based steel drum coating produced is easy to achieve 80g/L or less. In actual testing, the VOC of our water-based steel drum coating is about 40 g/L.
2, the construction of water-based steel drum coating (water-based color)
After several years of research and application, water-based monochrome steel drum coatings have been basically matured in monochrome barrel coating. Whether it is film performance or construction, it has been able to meet the quality requirements of steel drums. However, water-based color coatings have been successfully produced at present, and there is currently only one coating company for water-based steel drum coatings that have been in normal use for more than one year. The main reasons are:
1) The barrel of the color barrel has multiple colors. Since the barrel painting process is wet-on-wet construction and the interval time is short (about 20 seconds), the water-based paints of different colors are easy to penetrate each other, resulting in uneven color. The produced steel drum is unqualified;
2. Most of the color-filled barrels are yellow and white. Due to the poor hiding power of the two colors, the thickness of the two colors of the paint is thick, about 3 times that of other colors. The two colors of paint are significant. In this way, at a higher wet film thickness, coupled with a significant ratio, the two colors of water-based paint are highly prone to sag.
For bleed, we have solved this problem by adding a self-made additive to form a microscopic incompatible state in the two layers of wet film. For sagging, we have adjusted the body structure and linear structure types and proportions of water-based polyester resin, and supplemented with high-efficiency anti-sagging additives, which solved this problem well.
3. Shelf life of water-based steel drum coating
The shelf life of waterborne coatings is mainly related to the stability of the resin in water, in addition to factors such as pigments, auxiliaries and formulations. Water-based steel drum coatings generally use water-based polyester resin, and water-based polyester resin has a big problem to be solved, which is the problem of stability. Specifically, the ester bond is easily hydrolyzed in water, especially in an alkaline environment. However, the water-based paints are basically alkaline. After the ester bond is hydrolyzed, the molecular weight of the resin becomes small, which seriously affects the gloss, adhesion and corrosion resistance of the film.
Through molecular design, after many experiments and adjustments, the polyester molecules are spiraled in water, and the ester bonds are inside, so that the hydrophobic part is outside, thereby effectively shielding the water from destroying the ester bond, thereby extending the shelf life. . Through practical application, our company's water-based steel drum coating can guarantee the one-year shelf life, while the shelf life of other manufacturers' water-based steel drum coatings is up to 6 months, and some even only 3 months.
Fourth, the application cost and price issues
After solving the problems of performance and water-based color registration, whether the barrel-making enterprises can realize the “oil-to-waterâ€, and the equipment investment and production cost of the barrel factory need to be considered.
Since the water-based steel drum coating is in a liquid state like the solvent-based coating, the viscosity during construction is not much different, so that the barrel-making enterprise hardly needs to invest in the equipment.
In terms of cost, the cost and unit price of waterborne industrial coatings are currently higher than solvent-based coatings. However, since water-based paint is constructed with water as a diluent, the cost of water is much lower than the cost of the solvent, and the hiding power of the water-based paint is good, that is, the coating area of ​​the water-based paint is large, so that the water is used in comprehensive calculation. The overall cost of steel drum coatings is comparable to solvent-based coatings. Moreover, with the increase in the output of water-based industrial coatings, the prices of corresponding resins and additives will gradually decrease, the cost of water-based paints will gradually decrease, and the cost of coatings for coating companies will also decrease.
After solving the problems of quality, construction and cost, we began to vigorously promote the market. In one year, more than 30 companies use our company's water-based steel drum coatings, including some well-known barrel enterprises. Such as Tianjin Datian, Lanzhou Xingye, Zigong COFCO, Chengdu Haozu, Dalian Huinengda, Dadong Industry and Trade. At present, our company's water-based steel drum coatings monthly shipments of more than 100 tons, accounting for about one-tenth of the barrel paint market.
In summary, Hubei Jiaji Synthetic Material Co., Ltd. effectively solves many problems in the application of water-based paint in the steel drum industry, especially solving the problem of color-coating of water-based paint. The products have been successfully applied for many years in many barrel factories. , achieved good social and economic benefits.
Ceramic pots are not only exquisite in appearance, but also more ornamental when matched with cultivated flowers; ceramic pots will be stronger and more durable than other material flowerpots.
The forming process of ceramic flowerpots is also mainly purely hand-molded. Hand-molding uses hand-drawn blanks and sculptural skills. It has a deep artistic expression. Each piece is unique. Compared with other materials, the appearance of ceramic pots is better. Beautiful and elegant, suitable for living room, bedroom, outdoor, courtyard furnishings, the damage rate is relatively lower than that of glass, plastic materials, etc. The basin body does not fade, does not deform, and has good water retention. It is the best choice for various potted plants . Gather the spirit of heaven and earth, give pottery a unique spirit and charm, and demonstrate profound cultural heritage.
Ceramic Pots,Ceramic Flower Pots,Outdoor Ceramic Pots,Ceramic Flowerpot
Wuxi Shute Ceramic Products Co., Ltd. , https://www.stflowerpot.com