Application of environment-friendly cleaning agent and environment-friendly phosphor-free film agent

Application of environment-friendly cleaning agent and environment-friendly phosphor-free film agent

1. With the increasingly strengthening of environmental protection, the pollution of phosphorus has been highly valued by relevant departments and enterprises at home and abroad. In many regions and cities in China, the use of phosphorous detergent and phosphorous detergent is strictly prohibited. The environmental protection department is also increasingly strict with the requirements for the treatment of phosphorous in the wastewater after pretreatment before coating, resulting in a significant increase in the comprehensive cost of pretreatment before coating

2. The role of phosphorus in coating pretreatment agent

2.1 Phosphorus plays a very special role in traditional coating treatment agents, and its main role is shown in the following two aspects:

① Role in degreasing agent

It is mainly added to degreasing agent in the form of phosphate. The commonly used phosphate is sodium tripolyphosphate (Na5P3O10); Disodium hydrogen phosphate (Na2HPO4); Trisodium phosphate (Na3PO4), etc., whose functions in degreasing agents are emulsification, buffering and complexing, and have good water washability and low use cost, are the main components of phosphorus-containing degreasing agents, which is the main reason why phosphorus-containing degreasing agents still have a certain market. The prerequisite for manufacturing phosphate-free degreasing detergent is to synthesize new compounds that can replace phosphate. The compound with good emulsification, dispersion, softening of hard water and complex metal calcium, magnesium and iron ions has been successfully synthesized, and its degreasing ability is significantly better than that of single phosphate and composite phosphate, which is an ideal substitute for phosphate.

② Role in phosphating solution

Phosphorus is the most basic component and the most important component in the phosphating coating solution. It is the main film-forming substance of the phosphating solution. Commonly used include zinc dihydrogen phosphate and alkali metal phosphate, among which the commonly used alkali metal phosphate includes alkali metal first generation phosphate, alkali metal second generation pyrophosphate, alkali metal polyphosphate, etc. Phosphate coating agent can significantly improve the adhesion and corrosion resistance, and is a good substrate for coating film. However, due to the large amount of pollution source phosphorus, there are many sediment in the use process, and the environmental pollution is serious, which is strictly restricted by the relevant departments. In this case, if the performance of phosphating solution is maintained and phosphorus pollution is eliminated, it becomes an important research topic in the field of surface pretreatment at home and abroad.

3. The reason why phosphorus is strictly restricted by environmental protection

3.1 Overfertilization that cannot be overcome

Phosphorus-containing wastewater discharged into rivers and lakes will cause an increase in phosphorus content in water. Phosphorus is one of the three major nutrient elements for plant growth, thus promoting the reproduction and growth of algae in water. After a large number of algae have died, they release the erosive stench and cause anoxia in the water, which will lead to water pollution and adversely affect the growth of aquatic organisms. Therefore, the emission of phosphorus is strictly limited by environmental protection.

3.2 Deposition with metal ions

Phosphates combine with metal ions or produce chemical reactions to form phosphate deposits that are insoluble or insoluble in water. If it is not discharged in time, the phosphorous degreasing agent will easily block the nozzle when spraying, and the silicon zirconium coating agent will attach a large amount of sediment on the workpiece. If the cleaning is not complete, the treatment effect will be affected.

4. Characteristics of phosphorus-free pretreatment process

4.1 Realize phosphorus-free emission in the whole process.

The traditional coating pretreatment process, due to the large amount of phosphorus in the degreasing agent and the phosphating solution, leads to phosphorus pollution in the wastewater due to the tank liquid being carried out with the workpiece. Although the non-phosphorus degreasing agent has been rapidly applied in recent years, reducing phosphorus pollution to a certain extent, but because the phosphating solution still contains a large amount of phosphorus, the problem of phosphorus pollution in the coating pretreatment process has not been well solved. The application of non-phosphorus degreasing agent and non-phosphorus coating film solution has fundamentally solved the problem of phosphorus pollution in the pretreatment process of coating.

4.2 There is no need to modify the phosphorus-containing process

The non-phosphorus degreasing solution and non-phosphorus skin film solution only change the technical formula of degreasing agent and phosphating solution, without any change in the application process and conditions, so that the application process of non-phosphorus degreasing agent and non-phosphorus skin film solution is the same as the traditional phosphorus-containing process, the use temperature can be low and normal temperature, and there is no need for separate adjustment, and the tank solution management is more simple and convenient.

4.3 The treatment effect is consistent with that of phosphorus-containing process.

Phosphorus-free degreasing agent has good degreasing effect and longer service life than phosphorus-containing degreasing agent. It can be soaked or sprayed; The film layer of non-phosphorus coating solution is thin and appears blue and purple, and there is no hanging ash problem that affects the quality of phosphating. The bath solution has better stability, little sediment, and good adhesion, flexibility, and corrosion resistance of the film layer, which can be matched with painting, baking paint and plastic spraying.

4.4 Lower comprehensive cost.

Due to the realization of non-phosphorization in the whole process, the phosphorus element can not be treated separately for wastewater treatment. In addition, there is no zinc pollution, and the pH value of the tank solution is weak acid or neutral, so the wastewater treatment is greatly simplified; In the whole process, the separate surface adjustment is canceled, the bath solution has no pollution source zinc element composition, and will not produce phosphate deposition, which greatly reduces the cost of wastewater treatment.