1、 What is water-based paint

Waterborne paint is a type of paint that uses water as a diluent and does not contain benzene, toluene, xylene, formaldehyde, or free TDI toxic heavy metals. It is non-toxic and odorless, harmless to the human body, and does not pollute the environment. The paint film is full, shiny, transparent, flexible, and has characteristics such as water resistance, wear resistance, aging resistance, yellowing resistance, fast drying, and convenient use. It can be applied to various materials such as wood, metal, plastic, glass, and building exterior.

Waterborne paint is a film-forming material based on water-soluble resins, represented by polyvinyl alcohol and its various modifiers. In addition, there are also water-soluble alkyd resins, water-soluble epoxy resins, and inorganic polymer water-based resins.

1. The major advantage of water-based paint - environmentally friendly traditional oil-based paint contains over 85% organic solvents, while water-based paint only contains 10% organic solvents, resulting in lower VOC emissions. At the same time, water-based paint also has good paint layer characteristics, outstanding permeability and glossiness.

2. The disadvantage of water-based paint - compared to solvent based paint, water-based paint has the characteristics of low evaporation rate, high surface tension, high conductivity, corrosiveness, and easy occurrence of bubbles, resulting in differences in equipment and construction technology between water-based paint and solvent based paint.

2、 Technical Features of Waterborne Car Paint Spraying

The evaporation of water in water-based car paint is mainly controlled by adjusting the temperature and humidity of the spray booth, while solvent based paint can adjust the evaporation rate of the diluent to adjust the solid content applied. The solid content of water-based paint is generally 20-30, while the solid content of solvent based paint can reach as high as 60-70. Therefore, the smoothness of water-based paint is good, but it also needs to be heated and dried, otherwise it will simply present quality problems such as sagging and bubbles. Therefore, the control skills of paint rheology are the key to the design of water-based paint.

1.1 Equipment skill characteristics - The spray painting room and drying room are the primary ones, as the corrosiveness of water is greater than that of solvents, so the circulating water treatment system in the spray painting room needs to be made of stainless steel. Secondly, the air activity in the spray painting room should be excellent, with wind speed controlled between 0.2 and 0.6m/s, or air activity reaching 28000m3/h (which can be satisfied by normal paint baking rooms), In the same drying room, the high moisture content in the air can also cause corrosion to the equipment, so the walls of the drying room also need to be made of anti-corrosion materials.

1.2 Equipment skill characteristics - The temperature of the spray booth for active spraying system water-based paint spraying is 20 ℃~26 ℃, and the relative humidity is 60~75. The allowable temperature is 20-32 ℃, and the allowable relative humidity is 50-80%. Therefore, it is necessary to have appropriate temperature and humidity control equipment in the paint spraying room. The domestic car painting and painting rooms can adjust temperature and humidity in winter, but there are very few in summer because the cooling capacity required is too large, so there are few cooling air supply systems. Therefore, in areas with high temperature and humidity, if water-based paint is used, it is necessary to install air conditioning in the paint booth, and cool air is also required in summer to ensure the construction quality of water-based paint.

1.3 Equipment Skill Characteristics - Other Equipment

Hair dryer. Use mechanical methods to assist in accelerating the drying of the paint layer, such as specialized hair dryers. The control layer does not need to use mechanical methods to accelerate dryness.

Spray gun. Try to use a specialized spray gun with a pressure gauge as much as possible to ensure that the spray sample is consistent with the repair results. Before use, it is important to ensure that the spray gun is completely clean and dry with clean and dry air. This process is crucial for preserving the spray gun that has been cleaned with solvent.

Gun washing machine. Use a dedicated water-based gun washer to ensure that oily and sedan water-based paint waste are treated separately, and paint mixing containers and rods can also be cleaned in the gun washer. Tap water can corrode the gun body and should not be used to wash the gun.

Attention: Car water-based paint waste is not allowed to be discharged into the public drainage system.

2.1. The spraying of water-based paint on sedans adopts a gravity spray gun and two spraying methods (dry spraying and wet spraying).

2.2. Flashing drying of water-based paint for sedans: water-based paint and topcoat varnish are applied in a "wet to wet" manner, resulting in the problem of pre drying of water-based paint, which evaporates the majority of water and co solvents in the paint coating. The experiment indicates that the solvent content (mainly water) of water-based paint coatings should be reduced to less than 10%, so that the sprayed gloss varnish will not dissolve the paint layer again and cause water bubbles, which will affect the appearance quality. If flash dried under normal temperature conditions, the solvent content of water-based paint cannot reach below 10%. Therefore, it is necessary to perform appropriate forced drying before spraying glossy varnish on water-based paint. A common forced drying device is a hair dryer, and when using a hair dryer, the airflow direction blown out should be the same as the airflow direction in the paint baking room. The hair dryer should not be perpendicular to the paint surface, otherwise it will form paint defects. After the paint layer is full and dry, varnish spraying can be carried out.

Article source: Qingyuan Automotive Repair Paint http://www.jinliangxincai.com/