Read a article about water-based container coatings.

Since its inception in China in the 1980s, container manufacturing industry after more than 30 years of development, has become a mature industry,
every year there are 2.5 million to 3 million TEU of new container demand, the amount of paint required is 180,000 to 220,000 tons
, basically solvent-based coatings, about 95%. Traditional industrial coatings contain a large number of organic solvents, solvents in the construction and drying process are mostly waved out, which not only seriously pollutes the environment and harms human health, but also caused a great waste of resources. According to the data,
steel products and their facilities in the coating process volatile VOC total of about 20% to 25% of the global VOC total
, has become one of the main sources of air pollution

.
years, under the impetus of national
, various parts of china have promulgated environmental protection policies on "oil-to-water"
.
For the container coatings industry, in 2017 the China Container Industry Association in the industry to enforce the "no oil push water" policy and set industry standards, "box paint" has since entered the era of water-based coatings. After nearly two years of development, "box paint" has also been developed from the "two strong stand-by" to the "group male" era, of which the two strong refers to Dewey and KCC, group male refers to Zhong Tu chemical industry, COSCO Kansi, Mecca, Settai, Haihong, Haoli, Chenyang and other enterprises.
water-based container coating matching
according to industry standards, the current body paint system is generally used
"3 plus 2" supporting way
, of which "3" refers to the external matching three paint, respectively, two groups Part epoxy zinc-rich primer, single/double-part epoxy intermediate paint and acrylic outer paint, "2" refers to the two paints supporting the interior, respectively, two-part epoxy-rich primer and two-part epoxy interior paint. For intermediate paint, there is a choice of single parts, there are two parts.
water-based epoxy zinc-rich coating
Due to the presence of zinc powder, water-based epoxy zinc-rich coating can effectively cathode protection of the box, delay the progress of tank corrosion, prevent the paint film caused by bumps from falling off, so the system has been unanimously recognized by the east of the box.
water-based epoxy zinc-rich coatings, the main components
in addition to epoxy resin, curing agent, zinc powder and various additives
, live metal zinc powder can be chemically reacted with water, so there is zinc powder in the components, can not contain moisture , and epoxy resins and curing agents in epoxy coatings are not allowed in one part, so the formulation is designed with 2 ideas (
zinc powder and epoxy resin in one part; zinc powder and amine curing agent in one part).
because the water-based epoxy zinc-rich coating is to provide the main coating for the box corrosion, so the anti-corrosion performance of the product, mechanical performance for the formulation design points, at the same time to focus on the construction performance.
water-based interior paint
the main formulation system of water-based interior paint is:
water-based epoxy interior paint, water-based acrylic epoxy interior paint 2 kinds.
water-like epoxy interior paint
. The system is the original solvent-based system of paint water-based solutions, the main groups are divided into
water-based epoxy emulsion, water-based epoxy curing agent, rust-proof fillers, pigments, functional fillers and other components of
. Considering the stability of the system, the general use of self-emulsified epoxy emulsion, but at present it seems that most of the resin produced by domestic enterprises have some room for improvement.
water-based curing agents, the current paint suppliers are very different, but from the perspective of corrosion protection, water solubility is very good, low reaction activity curing agent
not suitable for
for water-based container paint. Due to the introduction of hydro-friendly groups, the corrosion resistance of water-based coatings is not as good as solvent-based under the same conditions.
water-based acrylic epoxy interior paint
. The system generally uses special acrylic resin as the main resin, and then introduces liquid epoxy for hybridization. The
advantage of the formulation system
is relatively low cost, but
taking into account the anti-corrosion factor
, currently accounting for more than 80% of the market share of mainstream paint suppliers, did not choose the system.
water-based intermediate paint
water-based intermediate paint main formula system is:
water-based epoxy intermediate paint, water-based acrylic epoxy intermediate paint, water-based acrylic intermediate paint 3 kinds of
.
water-based epoxy intermediate paint, water-based acrylic epoxy intermediate paint formula design ideas and water-based interior paint similar. The main resin of water-based acrylic intermediate paint is a high relative molecular quality acrylic emulsion, because acrylic emulsion and epoxy emulsion cost difference is huge, the cost advantage of the formulation system is obvious,
but with the improvement of domestic epoxy emulsion performance, the cost advantage has a downward trend
.
acrylic finish
water-based acrylic finish is divided into
pure acrylic emulsion, silicone emulsion and phenyl propylene emulsion
.
water-based acrylic paint is mainly to give the paint film excellent appearance, high weather resistance and water resistance and other properties. The weather resistance, water resistance and soil resistance of silicone emulsion are better than the other 2 kinds of emulsions, but the cost is higher due to the introduction of silane and so on.
, the performance and cost of pure propylene emulsion are more balanced, currently applied up to
;
acrylic paint in addition to emulsion parts, pigments are also an important part of the group. From an environmental point of view, the pigments currently used are heavy metal-free products, but some pigment stability has certain requirements for pH, so the formulation design needs to confirm and process the pH requirements of each pigment.
performance requirements and related standards
long-term paint film performance
long-term paint film performance mainly includes corrosion resistance, mechanical performance, weather resistance 3 aspects. The more authoritative testing standard is the IICL test conducted by KTA laboratory, and the requirements for the long-term performance of paint film in the JH/TE08-2015 "Container Water-based Coating Testing Methods and Acceptance Standards" developed by the China Container Association (CCIA) are mainly referenced for the long-term performance of the paint film.
different from the internal and external supporting systems, the test process methods are also different, the specific process is shown in the following diagram.
paint film acceptance standards and initial water resistance requirements
paint film acceptance is mainly on the paint film hanging state, pinhole / dark bubble state, color appearance, dew bottom situation and so on. The JH/TE08-2015 organization of the Container Association has carried out specific specifications on film thickness, adhesion, appearance and other requirements, for the industry's key reference standards, and some of the box East also has their own company's specific acceptance standards, respectively, the internal control indicators set. This article describes only the key items encountered in the actual application.
Pinholes, Dark Bubbles
Because of the influence of surfactants such as emulsizers, water-based coatings are more likely to produce bubbles, the performance of the film is pinholes, dark bubbles; At present, the main treatment method is to rely on additives to achieve, so that the cost of coatings has been greatly increased.
water resistance in the early stages
mainly includes the initial water resistance outside the box and water splashing experiments in the tank 2 aspects. Among them, the initial water resistance outside the box mainly for the container after the line of the weather continued to rain, the dryness of the paint film, the initial cross-link density, paint film water-soluble substance content, etc. put forward higher requirements;
IICL test methods and evaluation standards
the main problem of water-based container coatings
the supply of raw materials
resins, additives and other high value-added raw materials are mainly supplied by large foreign companies, because large international companies in water-based coatings technology for decades of technical accumulation, have some application experience, but this also provides a domestic technical enterprises a "sky high bird fly" market environment.
problem of high energy consumption
Compared with the use of three-spray-one-drying and fast-drying thinners in the original solvent-based system, the water-based system can only adjust the temperature and humidity by external heating and energy consumption. However, with the further promotion of clean energy in China, the application prospects of water-based coatings with low VOC emissions are more broad.
water treatment
because water-based coatings contain a certain amount of water-soluble substances, wastewater from water-based spraying processes is more difficult to treat than solvent-based wastewater. However, relatively speaking, container coating concentration is very high, sewage can be centralized treatment.
Infect disease control problems
because water-based paint on the temperature, humidity, the degree of gun mouth wear, etc. are more sensitive, with the change in temperature if not timely adjustment of the painting process, it is very easy to occur rough and hanging phenomenon. But at present, the mainstream water-based container coating suppliers have found a set of on-site control means, can predict related problems, to prevent batch problems, resulting in greater losses.
Conclusion
The current large-scale use of water-based container coatings, for the large-scale application of industrial coatings water-based, with the gradual accumulation of technical knowledge of coating research and development engineers, the expansion of raw materials technical performance, coating process further improve, water-based industrial coatings will further mature, thus making a great contribution to the greening of the coating industry.
.