The development of anti-rust-reinforced solvent-free epoxy anti-corrosion coating

Xie Yifu Zhanghu Li Guorong Feng GuoDaChen Liu Qihai
(Guangzhou Xiuper Chemical Co., Ltd., Guangzhou, Guangdong 511495)
Summary: epoxy resin as the base material, polyamide as a curing agent, the use of composite non-toxic environmental anti-rust pigment and with silicone titanium anti-rust enhancer, prepared an environmentally friendly solvent-free oxygen
anti-corrosion coating
. The effects of pigment quality fraction, curing agent type and dosage, active thinner dosage, fluidizer, different environmental protection anti-rust pigment combination, and silicon titanium anti-rust enhancer on the performance of
coatings
were discussed.
key words: solvent-free epoxy coating; Anti-corrosion coatings; Non-toxic anti-rust pigments; Silicon titanium anti-rust enhancer
: TQ630.7 Document identification code: A Article No: 1009-1696 (2013) 01-000 9-04
0 Introduction
In recent years, with the national attention to green ecological technology and people's awareness of environmental protection, environmentally friendly high-performance anti-rust anti-corrosion coatings have become an important direction and research focus of the development of anti-corrosion coatings technology. Rust-proof pigments are one of the basic ingredients of anti-rust and anti-corrosion coatings. Traditional rust-proof pigments can be divided into active and inert categories. Inert pigments act as fillers in the coating only shield and do not have chemical effects, and are not affected by climate, such as iron oxide red, aluminum powder, graphite and so on. Active pigments, such as red dan, zinc chromium yellow, zinc oxide, alkaline lead carbonate, etc., prevent corrosion by forming passivation membranes on protected metal surfaces, or metal soaps. Red dan and chromate pigments are toxic although they have good anti-rust effect. Red Dan can lead poisoning and damage children's intelligence; Hexavalent chromium salt carcinogenicity, has been banned in Europe and the United States, and in the eradication of such old paint skin, the entire object must be wrapped with a large curtain, the collection of old paint skin to prevent lead chromium chips into the river water or soil. In view of the lead, chromium rust-proof pigments to the environment caused serious pollution and endanger human health, the use of environmentally friendly composite anti-rust pigments instead of traditional anti-rust pigments has become an important means to develop environmentally friendly anti-rust anti-corrosion coatings. In addition, solvent-free and water-based has also become an environmentally friendly anti-rust anti-corrosion coating research and development direction.
is one of the most important and widely used anti-corrosion coatings in the world. Among them, solvent-free epoxy anti-corrosion coating has many advantages, such as excellent adhesion to a variety of substrates, excellent corrosion resistance and chemical resistance after curing coating, good film shrinkage, high hardness, especially its non-VOC (volatile organic compounds) emissions, do not cause environmental pollution, in line with environmental protection requirements. The outstanding advantages of solvent-free epoxy anti-corrosion coatings are also reflected in the mixing system can be cured at room temperature, curing time is reasonable, curing agent addition is wide and adjustable. In this paper, an environmentally friendly solvent-free epoxy anti-corrosion coating is prepared with epoxy resin as the base material, polyamide as curing agent, compound non-toxic environmental protection anti-rust pigment and anti-rust enhancer with silicon titanium. The effects of pigment quality fraction, curing agent type and dosage, active thinner dosage, fluidization aid, different environmental anti-rust pigment combinations, and silicon titanium anti-rust enhancer on coating performance were discussed.
1.1 Raw materials
polyamide curing agents: Versamid 140, Versamid 115, Versamid 125, Corning, Germany; Epoxy resin: EPON-828, Shell; Active thinner: XY748, Anhui Heng (new) Far Chemical Co., Ltd.;
pigment fillers
: iron red, modified aluminum tripolyphosphate, mica,
titanium white
; Anti-rust enhancer; Additives: Bick, Hemings; Inactive thinner: NX-2020, Madeleine.
1.2 Paint Formula
Coating Formulas can be found in Table 1.
Rust-resistant reinforced solvent-free epoxy anti-corrosion coating development
1.3 preparation process
A component preparation process: first part of the epoxy resin and de-foaming agent, dispersant mixed evenly, and then added pigment, grinding by the sander to fineness qualified, to produce color paste. In the stirring state, add the remaining amount of epoxy resin, flash inhibitor, tentacleant and leveling agent to the color paste, stir well and filter.
B component preparation process: the formulation of polyamide curing agent and inactive thinner mixed evenly. 1.4 Coating film performance test
hardness test reference GB/T673; The adhesion test on the makou iron refers to GB/T1720-1979; Paint film flexibility test reference GB /T1731-1993; Impact test reference GB/T1732-1993; Salt-resistant water immersion test reference GB/T1763; The salt-resistant fog test refers to GB/T1771-2007.
results and discussion
2.1 pigment dosage on coating performance
with EPON-828 epoxy resin, XY748 active thinner and epoxy curing agent Versami d140 as the base material, pigment selection of iron red, mica, rust-proof enhancer and modified aluminum tripolyphosphate .
the development of anti-rust-reinforced solvent-free epoxy anti-corrosion coating
the addition of pigment can affect the internal stress produced during the curing process of coating film, which is also an important factor affecting the adhesion of the coating. With the addition of pigment fillers, the shrinkage internal stress produced during the curing process of coating film is balanced, the adhesion is improved, and the flexibility of paint film is improved. Continue to increase the amount of pigment fillers, resulting in pigments can not be completely wrapped in resin, which in turn makes the physical and physical properties of the coating decreased. Comprehensive consideration, the selection of pigment quality score of 30% to 40% is appropriate.
2.2 different epoxy curing agents
tested using the German Koning Versamid series curing agents. Versamid curing agent is an active polyamide resin formed by the reaction of dijubo fatty acids and polyamides. It reacts with epoxy resins and cures at room temperature to form thermostat coating film with excellent flexibility and various resistances. Other factors in the formula remained the same, using different Versamid epoxy curing agents, and the results were found in Table 3.
The development of rust-resistant, solvent-free, solvent-free epoxy anti-corrosion coatings
as can be seen in Table 3: All kinds of epoxy curing agents produced paint film have excellent adhesion and physical mechanical properties, the destruction of salt spray test is mainly shown as foaming. The order of the anti-foaming effect is Versamid 140> Versamid 115>Versamid125. Taken together, Versamid 140 is chosen as the curing agent.
2.3 Effects of the ratio of curing agents to epoxy resins on the corrosion resistance of coatings
As can be seen from Table 4: appropriately increasing the equivalent ratio of curing agent and epoxy resin can help to improve the curing speed, cross-link density, drying speed, adhesion, solvent resistance and so on. However, polyamide curing agent itself has a certain amount of water solubility, such as its dosage is too much, will affect the physicochemical properties of the paint film, such as paint film hair adhesion, salt water resistance, salt spray resistance decline. Table 4 shows that the ratio of curing agent to epoxy equivalent is appropriate (0.9 to 1.05):1.
The development of anti-rust-reinforced solvent-free epoxy anti-corrosion coating
2.4 effect of active thinner dosage on coating performance
Epoxy EPON-828 color paint has a large viscosity, which must be properly diluted for ease of use. If organic solvents are used, the organic volatile content of the coating will be increased and the tightness of the coating will be reduced. Active thinners are long-chain compounds with low viscosity of monoethic oxygen erythrial groups, which can reduce the viscosity of epoxy resins, mix with curing agents and participate in cross-linking reactions, while acting as a toughening agent. In the experiment, the low odor, low volatile C12-14 alkyl shrinking glycelor ether XY748 was used as an active thinner to investigate the effect of its dosage on the paint-related properties, and the results were found in Table 5.
the development of rust-resistant solvent-free epoxy anti-corrosion coatings
as can be seen in Table 5: With the increase in the amount of active thinners, the viscosity of component A decreases, the gel time is extended, and the hardness is reduced. The active thinner XY748 is a single-cell energy compound, the increase of its dosage will reduce the curing crosslink density, but its appropriate dosage can not only reduce viscosity, improve the flexibility of the paint film, but also ensure that the paint film has a higher hardness. Taken together, the amount of XY748 is 5% to 15% (quality score).
2.5 flow aid on coating performance
The flow aid mainly affects the anti-subsidization of paint storage and the anti-flow hanging of the construction process. Since most of the anti-corrosion engineering construction work surfaces are facades, and epoxy anti-corrosion coatings of a single dry film thickness of 40 to 60 m, which requires the coating must have good anti-flow, therefore, we used for the formulation of the fluid additive screening, the results can be seen in Table 6.
can be seen by Table 6: in the epoxy coating system,
blow soil
anti-subsidy and anti-flow hanging performance is excellent, no adverse effects on the paint status and curing, suitable for spray construction; The BYK-410 can opens in good condition and is suitable for brushing.
effect of 2.6 composite anti-rust pigments on the corrosion resistance of coatings
Anti-rust pigments can be divided into physical rust-proof pigments and chemical anti-rust pigments. Relying on an inert rust-proof pigment alone can not meet the requirements, must use active rust-proof pigment compounding. The anti-rust enhancer used in the experiment is a specially treated silicon-titanium compound, which can be added to further improve the anti-rust capability of the coating film. On the one hand, the fine active ingredient in the rust-proof pigment can react with the moisture medium in the air to form an insoluble substance, which clogs and closes the pores and micro-cracks in the paint film, blocking the erosion of the substrate by harmful substances such as moisture; On the other hand, the rust-proof pigment can be mediumed free acid, atmospheric carbon dioxide into the paint film, blocking the formation of alkaline carbonate on the iron surface, and can form a passivation film with the iron substrate surface so that the substrate is protected. The effect of different composite anti-rust pigments on the anti-corrosion properties of the coating film was examined, and the results were found in Table 7.
can be seen by Table 7: Compared with iron red, modified aluminum tripolyphosphate, anti-rust enhancer with the best anti-corrosion performance, the three have a synergetic anti-rust effect.
3. Conclusion
(1) Through formulation optimization, using non-toxic compound rust-proof pigment and low odor, low volatile activity thinner, developed an environmentally friendly epoxy anti-corrosion anti-corrosion coating, the test results show that the paint anti-corrosion performance is excellent.
(2) the anti-rust enhancer of silicon-titanium composites further enhances the anti-rust performance of the coating.
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