Water-based, powder environment-friendly FEVE fluorocarbon resin synthesis technology and coating application progress (I)

 The paint industry "oil to water" and "paint to powder" have become popular research topics in recent years.

The development and application of water-based FEVE fluorocarbon resin coatings has a history of more than 10 years.

1 Synthesis and application of water-based FEVE fluorocarbon resin

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The molecular structure of the resin essentially determines the performance of the water-based FEVE fluorocarbon resin coating

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The polymerization methods of water-based FEVE fluorocarbon resin dispersion mainly include emulsion polymerization and solution polymerization

In classic emulsion polymerization, the emulsifier is an indispensable component in the polymerization formula.

The solution polymerization method is initiated by an organic peroxide type oily initiator, a single or mixed solvent of water-soluble alcohol ether, alcohol or ester, and ketone is used, and the molecular weight of the resin is controlled by a molecular weight regulator

Table 1 Comparison of main characteristics and performance of water-based FEVE fluorocarbon dispersion

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The development of water-based one-component self-crosslinking FEVE fluorocarbon resin has two stages

The first stage: use chlorotrifluoroethylene, vinyl acetate, diacetone acrylamide (DAAM) as the main comonomers, with some acrylates, undecylenic acid, etc.
, plus emulsifiers, and use emulsion polymerization to synthesize water-based monomers.
The components are self-crosslinking FEVE fluorocarbon emulsion
.
The water-based one-component self-crosslinking FEVE fluorocarbon emulsion is moderately crosslinked, with low gloss, generally less than 40°, and general water resistance.
It is mainly designed for building exterior wall protective coatings
.

The second stage: In recent years, the demand for water-based industrial coatings has increased.
Many domestic and foreign manufacturers have introduced water-based one-component self-crosslinking acrylic dispersions by solution polymerization and internal emulsification, which have been applied in the field of water-based wood coatings
.
Aqueous one-component self-crosslinking FEVE fluorocarbon resin dispersion, using solution polymerization external emulsification or internal emulsification
.
The external emulsification method redesigns the molecular structure of the resin and introduces ethylene tertiary carbonate to increase the steric hindrance effect of the macromolecular chain, weaken the interaction between the macromolecules, and significantly reduce the surface tension of the polymer
.
The unique shield effect of tertiary carbon atoms gives polymers excellent water resistance and weather resistance
.
The internal emulsification method introduces new macromolecular reactive hydrophilic monomers into the resin structure to further improve the overall performance of the resin such as water resistance
.
After mixing DAAM and adipic acid dihydrazide (ADH) in the resin main chain structure, self-crosslinking at room temperature and rapid crosslinking at heating can be realized
.
DAAM and ADH in the dispersion can be stored stably at room temperature due to the inhibition of water and weak alkaline environment.
During the film formation process, the crosslinking reaction can occur due to the volatilization of water, forming a stable three-dimensional network structure
.

During the synthesis process of the water-based one-component self-crosslinking FEVE fluorocarbon resin dispersion, the molecular weight is controlled to be moderate and uniform, with high gloss and full film formation
.
Table 2 shows the main technical indicators of the water-based one-component self-crosslinking FEVE fluorocarbon dispersion
.

Table 2 Main technical indicators of water-based one-component self-crosslinking FEVE fluorocarbon dispersion

The performance of the water-based one-component self-crosslinking FEVE fluorocarbon resin dispersion paint is the same as that of ordinary fluorocarbon emulsion, and the additives used in the formulation are the same as those of ordinary latex paint, which is easy to use
.
The coating performance meets the requirements in the HG/T4104 standard, and the aging performance is better than that of fluorinated acrylic emulsion
.
Table 3 shows the reference formulation of the water-based one-component self-crosslinking FEVE dispersion coating
.

Table 3 Reference formula of water-based one-component self-crosslinking FEVE dispersion coating

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3 Aqueous two-component FEVE fluorocarbon resin dispersion

The aqueous two-component FEVE fluorocarbon resin dispersion is usually prepared by solution polymerization and external emulsification
.
In recent years, as multiple hydrophilic functional vinyl ether/ester monomers suitable for fluorocarbon structures have been successfully developed, the selectivity of hydrophilic monomers and polymerization processes has increased
.
Water-based two-component FEVE fluorocarbon resin dispersions mainly include chlorotrifluoroethylene-vinyl ester FEVE and chlorotrifluoroethylene-vinyl ether FEVE
.
Trifluorochloroethylene-vinyl ester FEVE fluorocarbon resin dispersion, with chlorotrifluoroethylene and vinyl acetate as the main comonomers, through functional vinyl tertiary carbonate monomers, olefinic acid, hydroxyl monomers, hydrophilic The vinyl ester macromonomer balances the hydrophilicity of the resin and other physical and mechanical properties
.
The comprehensive performance of the water-based two-component ester FEVE fluorocarbon resin dispersion is close to that of the same solvent-based ester FEVE fluorocarbon resin
.
Due to the need to have a certain amount of relatively large molecular weight balanced hydrophilic and functional monomers in the structure, the fluorine content of the resin is slightly lower (fluorine content, about 22%)
.
In addition, the main comonomer vinyl acetate has the characteristics of the bulk, the dispersion color is darker in the alkaline system, from light yellow to yellow
.
When the temperature is higher than 170℃, the color of the resin changes greatly in the water-based high-temperature system, which is not suitable for varnish and high-temperature baking paint
.
Trifluorochloroethylene-vinyl ether-based FEVE fluorocarbon dispersion, with chlorotrifluoroethylene-vinyl ether as the main comonomer, rationally designed through acrylic acid, vinyl ether macromolecular hydrophilic monomer, and hydroxyl monomer Resin structure, balance hydrophilicity and other properties
.
The comprehensive performance of the water-based two-component ether-based FEVE fluorocarbon resin dispersion is also close to that of the same solvent-based ether-based FEVE fluorocarbon resin
.
Alkali is a vinyl ether monomer stabilizer, therefore, the dispersion is light in color under alkaline system conditions, from colorless to pale yellow
.
Ether FEVE fluorocarbon dispersion has high fluorine content (fluorine content, about 25%), good high temperature yellowing resistance, suitable for varnish and high temperature baking paint
.
In addition, during the test evaluation process, it was found that there is still a certain gap between the stability of conventional ether dispersions and ester dispersions during the construction and application process.
For example, the gloss and performance of the coating film decreased during the construction process.
Functional monomer can solve this problem
.
Table 4 shows the main technical indicators of water-based ester and ether FEVE fluorocarbon resin dispersions
.

Table 4 Main technical indicators of water-based ester and ether FEVE fluorocarbon resin dispersion

In the synthesis process of water-based two-component FEVE fluorocarbon dispersion, it is often encountered that the viscosity of the water-added dispersion is too high.
To reduce the viscosity of the dispersion, it is necessary to adjust the cosolvent content, reduce the molecular weight of the resin or adjust the molecular structure of the resin
.
Reducing the molecular weight of the resin generally sacrifices the performance of the coating film, and it is preferable to improve the viscosity of the dispersion by adjusting the molecular structure of the resin
.
The choice of water-based two-component ether FEVE fluorocarbon dispersion raw materials is narrow, and some newly developed special function raw materials have not yet been commercialized on a large scale, and the raw material supply cycle is long
.

The copolymerization and reactivity ratio of FEVE fluorocarbon resin and acrylic resin are quite different
.
It is difficult to achieve core-shell structure or interpenetrating network (IPN) resin technology during the synthesis process .
The physical hybridization of water-based two-component FEVE fluorocarbon resin dispersion and water-based hydroxy acrylic resin is a reasonable method
.
Physical hybridization is the physical mixing of two emulsions in a certain proportion through a special process.
Process control is used to make FEVE resin and acrylic resin molecules entangle with each other to achieve an IPN structure, which can be used in paint making performance, construction application performance, and coating physical and chemical properties.
Complementary advantages in other aspects, while reducing production costs
.

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4 Performance and application of water-based two-component FEVE fluorocarbon dispersion coating

The coating is prepared with water-based two-component FEVE dispersion, and matched with a water-based epoxy primer coating system.
The performance of the composite coating system is tested according to the HG/T3792-2014 standard, and all performance indicators can reach the solvent-based coating standard
.
Table 5 shows the coating properties of the aqueous two-component FEVE fluorocarbon dispersion
.
Figure 1 shows the comparison of water-based two-component white paint and artificial accelerated aging data
.

Table 5 Coating performance of water-based two-component FEVE fluorocarbon dispersion

Figure 1 Artificial accelerated aging gloss retention curve of water-based FEVE resin

Remarks: DF is a water-based two-component FEVE fluorocarbon series product

As shown in Figure 1, the water-based FEVE white paint is compared with the artificial accelerated aging analysis, and the water-based aging data is close to the current solvent-based FEVE level
.
Water-based FEVE dispersions and water-based hydroxy acrylic acid have similar problems in actual use, such as short pot life, thick coatings are prone to rashes, etc.
The entire downstream industry has a relatively low awareness of water-based, and solvent-based construction conditions are still used.
To require water, the industry also needs to increase efforts to guide and promote
.
At present, the main application directions of water-based two-component FEVE dispersion are mainly concrete protection, water-based steel structure, outdoor machinery, aluminum and other industries
.