Epoxy paint for cast iron pipes and fittings for building drainage, its preparation and application

Abstract

The present invention discloses epoxy paint for cast iron pipes and cast iron fittings for building drainage, and its preparation and application. The epoxy paint of the present invention comprises a liquid epoxy resin and a modified polyamide curing agent, wherein the modified polyamide curing agent is prepared by uniformly mixing a first mixture and a second mixture in proportion; wherein the first mixture is a mixture of polyamide and a polyamide adduct, wherein the polyamide adduct is obtained by an addition reaction of polyamide with a multifunctional glycidyl ether; and the second mixture is a mixture of an organic amine having a cyclic structure and an organic amine adduct, wherein the organic amine adduct is obtained by an addition reaction of an organic amine having a cyclic structure with a flexible glycidyl ether. The performance of the coating formed by using the epoxy paint of the present invention on cast iron pipes and cast iron fittings for building drainage meets the BS EN 877 standard, especially in terms of resistance to cold and hot alternating cycles and salt spray resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to a coating composition based on epoxy resin. Background Art

[0002] The drainage system has always been a major component closely related to human production and life. With the continuous progress of society and the continuous improvement of public demand, the drainage system has also evolved from the most primitive open type in the early days to a closed type, and the infiltration discharge type has been improved to a leakage-free discharge. The material has changed from the early mud, wood, and pottery to the metal and other materials used today, which has greatly improved the impact of environmental pollution on our public health. With the rapid development of global economic construction and the improvement of people's living standards, the requirements for buildings are also getting higher and higher. A smooth and lasting drainage system is one of the important infrastructures of a building or even a city, and it is also a strong guarantee for people's life and production.

[0003] Before the 1970s, cast iron pipes and fittings were used in most building drainage, sewage and ventilation systems around the world. After that, plastic (ABS or PVC) pipes began to be used in buildings. However, the noise and fire safety problems caused by plastic pipe systems are more serious and prominent. At present, the level of urban construction is constantly improving, and more stringent requirements are put forward for the construction quality and product standards of water supply and drainage systems. The functions of urban construction drainage systems in the new era are also gradually improving in the face of challenges. From drainage in civilian kitchens and toilets to the discharge of special pollutants such as large canteens, hospitals and laboratories, higher requirements are put forward for the pressure bearing, corrosion, leakage, fire resistance and service life of pipes. With the improvement of cast iron pipe production technology, cast iron pipes have many advantages such as high strength, long life, low noise, strong flame retardancy and fire resistance, flexible earthquake resistance, no secondary pollution, and renewable recycling, which have been recognized by society and the market again. They are currently widely used in high-rise residential buildings, airports, gymnasiums, hospitals, schools and municipal engineering.

[0004] Cast iron pipes are selected as the material for building drainage pipes. Compared with other metal pipes and plastic pipes, they have some unique advantages. The specific excellent characteristics are as follows:

[0005] ①Excellent corrosion resistance

[0006] According to common sense, people think that cast iron pipes will rust and their corrosion resistance is not as good as plastic pipes. This is due to cognitive misunderstandings and misleading propaganda. In fact, the corrosion resistance and aging resistance of cast iron drainage pipes cannot be replaced by other chemical pipes. Cast iron drainage pipes are made of gray cast iron. Gray cast iron is different from ordinary steel. It generally contains 2.5% to 4% carbon, and all or most of the carbon exists in the form of free graphite in the gray cast iron structure. The volume of this part of free graphite carbon accounts for about 10% of the gray cast iron. During the corrosion process, the iron element on the surface of the cast iron is corroded, and the insoluble graphite layer is left behind. This layer of graphite remains is firmly attached, strong, and dense, and becomes a protective layer on the surface of the casting to prevent further corrosion. Ordinary steel has a lower carbon content and does not exist in the structure in the form of free graphite. It cannot form a graphite protective layer and has poor corrosion resistance. This is why gray cast iron drainage pipes have superior corrosion resistance.

[0007] ②Excellent aging resistance

[0008] Unlike polymer chemical pipes, cast iron drainage pipes will not age with the extension of use time, changes in temperature and sunlight exposure, and have a long service life. At present, many building exterior wall rainwater pipes in my country use plastic pipes, which will age and crack with seasonal temperature differences and sunlight exposure. If ordinary steel pipes are used, their corrosion resistance cannot meet the requirements. Cast iron drainage pipes have unique advantages in aging and corrosion resistance, and are the best choice for exterior wall rainwater pipes.

[0009] ③Excellent strength and wear resistance

[0010] The tensile strength of cast iron drainage pipes is generally greater than 150MPa, which is 3 to 4 times the strength of chemical drainage pipes such as PVC. It has good compressive resistance during underground pipeline construction and can prevent tree root penetration and rodent gnawing and damage. The excellent strength and wear resistance of cast iron drainage pipes enable it to better resist the impact and abrasion of mud, gravel, glass fragments, ice particles and food residues in sewage and rainwater, ensuring the reliability of the drainage system under various harsh conditions.

[0011] ④Excellent quiet performance

[0012] As we all know, cast iron drainage pipes are excellent silent pipes. On the one hand, due to the dense structure of gray cast iron and the unique flake graphite structure, it can effectively absorb the energy generated by vibration and greatly reduce the propagation of noise. On the other hand, at present, cast iron drainage pipes are mostly connected by rubber sealing interfaces. This flexible connection method can effectively block the propagation of water flow sound in the pipe. Research by the American Cast Iron Drainage Pipe Association has shown that the efficiency of flexible cast iron drainage pipes in blocking noise propagation is 7.5 times that of other chemical pipes. The noise used in drainage systems is 6 to 10 decibels lower than that of PVC pipes. This is why you often hear loud water flow noise when using plastic drainage pipes, but it is very quiet when using cast iron drainage pipes.

[0013] ⑤Excellent fire resistance

[0014] Cast iron pipe systems have many advantages over other alternative materials in terms of fire-resistant construction. Cast iron pipes are non-flammable, which has two obvious advantages in the event of a fire: one is that it can prevent the spread of fire; the other is that it can avoid the use of plastic pipes that produce toxic gases when burned, which endangers the lives of residents and firefighters. Cast iron pipes can effectively prevent the spread of fire. Building fire regulations require that modern building designs should provide fire safety protection for residents, giving them the opportunity to avoid fire damage in the event of a fire. Therefore, the various compartments of the building are designed to provide a fire barrier for a specific period of time. This fire barrier must be relatively closed to prevent the spread of fire and smoke from one place to another. To ensure the barrier effect of the fire isolation zone, in addition to automatic fire doors, it is also necessary to prevent the spread of fire and smoke to other areas through the pipe installation holes that pass through the building floor. At present, many high-rise buildings use a large number of plastic drainage pipes. These pipes are easy to burn in the event of a fire, forming holes that pass through the floors in the kitchen and bathroom. These holes destroy the fire barrier of the building. The chimney effect caused by the temperature difference in these holes intensifies the spread of fire and smoke to the upper floors of the building, making the residents who are affected by the fire lose the opportunity to hide and escape. Cast iron drainage pipes are fire-resistant, non-flammable, and high-temperature resistant. They can effectively maintain the barrier effect of the fire barrier between floors and win precious rescue time for residents. Cast iron pipes can also avoid the harm of toxic smoke. As a modern building to ensure the safety of people's homes, fire safety should be the first task. When plastic pipes burn, a large amount of toxic smoke is produced, which is easy to spread; while the non-flammable nature of cast iron drainage pipes prevents them from producing toxic smoke. At present, many high-rise buildings in China use a large number of plastic drainage pipes in order to reduce construction costs. The main reason is the lack of strict fire protection and fireproof material certification and construction acceptance system for high-rise buildings using plastic pipes. On the contrary, developed countries have formulated strict fire safety and fire prevention regulations and certification and acceptance system regulations for the use of plastic pipes in high-rise buildings, which not only include the flame retardant performance of pipes and fireproof ring performance, but also have strict fire acceptance regulations for fire isolation measures for plastic pipes during installation and construction. The construction cost is not lower than that of cast iron pipes. Therefore, developed countries still mainly use cast iron drainage pipes in high-rise fire-resistant buildings.

[0015] ⑥ Cast iron drainage pipes are the best choice for earthquake-resistant buildings

[0016] At present, the cast iron drainage pipes promoted and used in my country are all flexible joints, which are a new type of earthquake-resistant cast iron pipes. my country began to study and introduce this product technology in the early 1980s, and proved through experiments that flexible joint cast iron drainage pipes are safe for use in areas with an earthquake intensity of 9. In the Wenchuan earthquake in my country, many buildings using plastic drainage pipes experienced drainage pipe ruptures and leaks, while the drainage systems of buildings using flexible joint cast iron drainage pipes did not experience pipe ruptures and leaks. Practice has proved that flexible joint cast iron drainage pipes are the best choice for earthquake-resistant buildings.

[0017] ⑦ Smaller thermal deformation coefficient can ensure safe and reliable operation of the pipeline. Plastic pipes have a large thermal deformation coefficient, which may cause pipe rupture and leakage during use due to temperature difference deformation and the large difference in thermal deformation coefficient with cement structures. Relatively speaking, the thermal expansion coefficient of cast iron drainage pipes is only about one-ninth of that of PVC plastics, and is similar to that of cement structures. In addition, the deformation compensation function of the flexible interface of cast iron drainage pipes can ensure the safety of pipeline operation even without any deformation compensation device in the pipeline system.

[0018] ⑧ Cast iron drainage pipes are the best choice for green buildings

[0019] Scrap cast iron drainage pipes can be 100% recycled and remelted without causing secondary pollution to the environment. In some developed countries and countries with a shortage of pig iron resources, scrap steel is the main raw material for the production of cast iron drainage pipes. Therefore, cast iron drainage pipes are not only recyclable and environmentally friendly materials, but their production process itself provides a broad way to reuse a large amount of scrap steel, greatly saving pig iron and coke resources and reducing carbon emissions. Their contribution to environmental protection far exceeds their own recycling value, and they are the best choice for green buildings.

[0020] Qualified cast iron pipes can be used for more than a hundred years, but it is inevitable that cast iron pipes without anti-corrosion treatment will rust, which is also the most prominent defect of cast iron pipes. Qualified anti-corrosion coatings can effectively resist rust and corrosion of cast iron drainage pipes. In order to continuously meet the needs of growing development, some developed countries in Europe and the United States started research in this field early and achieved remarkable results. In the industry, France's Saint-Gobain (Saint-Gobain) took the lead in winning breakthroughs in coating materials and coating processes for cast iron drainage pipes, which brought the salt spray resistance, chemical resistance, wastewater resistance, hot water resistance, alternating hot and cold changes of the inner coating of the pipe to a new level, and thus formed a new industry standard. At present, the domestic requirements for coating and anti-corrosion of cast iron drainage pipes are relatively low, and generally implement GB / T 34202-2017 "Epoxy Coating (Heavy Anti-Corrosion) of Ductile Iron Pipes, Fittings and Accessories". However, in the high-end pipeline matching market in Hong Kong, Macao and Europe, the coating and anti-corrosion of cast iron drainage pipes are carried out in accordance with the British standard BS EN 877: 1999 + A1: 2006 "Cast iron pipes and fittings for drainage from buildings - Requirements, test methods and quality assurance". For example, the standard "BS EN 877-1999 + A1-2006 Cast iron pipes and fittings, their joints and accessories for the evacuation of water from buildings - Requirements, test methods and quality assurance" has provisions for the temperature cycle test of drainage pipes, mainly considering that people have a wide temperature range in daily water use and that domestic drainage has alternating hot and cold water. The temperature cycle test method specified in the EN877 standard is as follows: (30 ± 1) L, (93 ± 2) ℃ water, continuously flows through the pipeline system for 1 minute; empties and stays for 1 minute; (30 ± 1) L, (15 ± 5) ℃ water, continuously flows through the pipeline system for 1 minute; empties and stays for 1 minute; cycles 1500 times. In 2021, this standard has a new version: BS EN 877:2021 Cast iron pipe systems and their components for the evacuation of water from works-characteristics and test methods. The performance requirements for coatings in the 2021 version of BS EN 877 have basically not changed.

[0021] In the past 20 years, the world economy has developed rapidly, but my country's increasingly prosperous pipeline industry has not been able to share the technology and products of coatings. The industry's technical barriers have become a bottleneck for our development, making it difficult for my country's pipeline products to go abroad. Otherwise, it will cost a lot, so that going abroad is also low-efficiency or low-end non-standard industry fields, without competitive advantages. Before 2019, the building pipeline industry used a large number of powder coatings. As time went by, when the quality effect of the product was verified, it was found that the quality problems of the powder coating pipeline system installed in the building were presented in different forms: coating shedding; inner wall rust, sealing area leakage, etc. Through the combing of many cases, it was found that the coating of the powder coating pipeline before installation and construction was brittle and weak in flexibility, and it was easy to break when bumped, which caused the coating to fall off in a large area. It was not easy to repair the construction site, which buried the hidden danger of further rust in the later use. Further tests proved that the powder coating could not withstand the test in terms of quality stability in terms of resistance to cold and hot alternation, wastewater and salt spray. If the powder material is improperly designed and selected, and the process control is slightly deviated, the adhesion of the powder coating will be greatly affected, the coating is easy to peel off, and it is easy to bubble and rust in the fluid medium environment. It is difficult to meet the requirements under multiple conditions of industry standards. In addition, the powder coating application process has problems such as high curing temperature, narrow curing temperature range, difficult process control, high energy consumption and missing coating points.

[0022] In order to better solve the problem of pipe coating and meet the requirements of international standards (such as BS EN 877), new coating materials for cast iron pipes and cast iron fittings for building drainage must be developed. Summary of the invention

[0023] In view of this, the object of the present invention is to provide an epoxy paint for cast iron pipes and cast iron fittings for building drainage, and its preparation and application. The performance of the coating formed by the epoxy paint on the cast iron pipes and cast iron fittings for building drainage meets the BS EN 877 standard, especially in terms of resistance to hot and cold alternating cycles and salt spray resistance.

[0024] In a first aspect of the present invention, an epoxy paint is provided, comprising a liquid epoxy resin and a modified polyamide curing agent, wherein the modified polyamide curing agent is obtained by uniformly mixing a first mixture and a second mixture in proportion; wherein the first mixture is a mixture of polyamide and a polyamide adduct, wherein the polyamide adduct is obtained by an addition reaction of the polyamide with a multifunctional glycidyl ether; and the second mixture is a mixture of an organic amine having a cyclic structure and an organic amine adduct, wherein the organic amine adduct is obtained by an addition reaction of the organic amine having a cyclic structure with a flexible glycidyl ether.

[0025] In some specific examples of the present invention, the multifunctional glycidyl ether is a phenolic epoxy resin, and the organic amine having a cyclic structure is cyclohexanediamine.

[0026] In some specific examples of the present invention, the functionality of the polyamide adduct is 20-30, and the functionality of the organic amine adduct is 6-8.

[0027] In some specific examples of the present invention, the modified polyamide curing agent is prepared by the following method:

[0028] (1) adding 56 g of xylene and 24 g of n-butanol to a reaction container containing 400 g of polyamide, controlling the temperature at 40° C. to 50° C., and then slowly dropping a phenolic epoxy resin liquid therein, wherein the phenolic epoxy resin liquid is composed of 55.2 g of xylene and 32 g of phenolic epoxy resin, and keeping the temperature for 4 to 6 hours after the dropping is completed; then, raising the temperature to 100° C. and keeping the temperature for 1 hour to obtain a first mixture;

[0029] (2) adding 54 g of flexible glycidyl ether dropwise to a reaction vessel containing 300 g of cyclohexanediamine, controlling the temperature at 30° C. to 40° C., and keeping the temperature for 3 to 4 hours after the addition is complete, then raising the temperature to 80° C. and keeping the temperature for 2 hours to obtain a second mixture;

[0030] (3) The first mixture and the second mixture were mixed at a mass ratio of 100:27, and stirred at 50° C. for 1 hour to obtain the modified polyamide curing agent.

[0031] In some specific examples of the present invention, the modified polyamide curing agent has a solid content of 80%, an amine value of 325 mg KOH / g, and an active hydrogen equivalent of 90 Wt%.

[0032] In some specific examples of the present invention, the liquid epoxy resin is bisphenol A type liquid epoxy resin.

[0033] In some specific examples of the present invention, the liquid epoxy resin is liquid epoxy resin E51.

[0034] In some specific examples of the present invention, the liquid epoxy resin E51 has an effective mass solid content of 100%, an epoxy equivalent of 184-194 g / eq, a viscosity of 11500-15000 CPS / 25° C., and hydrolyzable chlorine ≤1000 ppm.

[0035] In some specific examples of the present invention, the epoxy paint comprises, by mass percentage:

[0036] Liquid epoxy resin: 13.19-23.45%;

[0037] Organic solvents: 20.67-34.13%;

[0038] Pigments, including: iron oxide pigments 0-11.37%, rutile titanium dioxide 0-12.55%, carbon black 0-0.42%;

[0039] Filler, including: 20.08-37.24% of precipitated barium sulfate and 4.52-7.04% of wet-process mica powder;

[0040] Additives: 2.43-4.22%;

[0041] Modified polyamide: 5.17-10.46%;

[0042] The sum of all components in the epoxy paint is 100%.

[0043] In some specific examples of the present invention, the organic solvent includes one or more of benzene, alcohol and ketone organic solvents; preferably includes one or more of xylene, 100# solvent oil (also known as trimethylol solvent oil), n-butanol, cyclohexanone and the like.

[0044] In some specific examples of the present invention, the auxiliary agent includes one or more of a thixotropic agent, a pigment and filler wetting and dispersing agent, a defoaming agent and an adhesion promoter.

[0045] In some specific examples of the present invention, the auxiliary agent includes a thixotropic agent, a pigment and filler wetting and dispersing agent, a defoaming agent and an adhesion promoter.

[0046] In some specific examples of the present invention, the thixotropic agent is a polyamide wax slurry, which can be effectively dispersed in the paint system to form a strong network structure, has excellent thixotropy and anti-rheological properties, and not only has excellent anti-settling performance, but also can effectively prevent the thick coating sagging phenomenon during paint construction.

[0047] In some specific examples of the present invention, the pigment and filler wetting and dispersing agent is at least one of an unsaturated polyacid polymer, a copolymer solution containing an acidic group, a polymer polyurethane block polymer, and a multi-chain polymer block polymer solution containing a pigment affinity group. The pigment and filler wetting and dispersing agent is preferably a mixed solution of an unsaturated polyacid polymer and an organosilicon polymer, which can reduce the interfacial tension between the pigment and filler and the resin, and can not only reduce the viscosity of the paint system, but also effectively disperse and stabilize the coloring pigment and filler, so that the coloring pigment can fully exert its color development and ensure the stability of the paint film color. The pigment and filler wetting and dispersing agent is more preferably Tiger additive Tech-5065, which can achieve high wetting and dispersing efficiency at a very small dosage, "controllable flocculation" of the dispersed pigment, and prevent the floating color and blooming of the pigment. Moreover, the small amount of organosilicon copolymer it contains helps to prevent Bénard vortices and streaks, improves surface smoothness, and is conducive to the film-forming orientation of the powder.

[0048] In some specific examples of the present invention, the defoamer is at least one of silicone oil, modified foam-breaking polymer silicone solution, foam-breaking polysiloxane solution and foam-breaking self-emulsifying polyether solution. The defoamer is preferably an organic modified foam-breaking polysiloxane solution, which has a good balance in compatibility and high-efficiency foam suppression and defoaming properties, and can effectively eliminate the foam generated during production and construction. The defoamer is preferably Tech-367N, a Tiger additive.

[0049] In some specific examples of the present invention, the adhesion promoter is a silane coupling agent A-187 with an epoxy group, and its chemical silane bond -Si-O-CH 3 It is very easy to hydrolyze and effectively improve the wet adhesion and cohesion of the paint film.

[0050] In a second aspect of the present invention, the present invention provides a coated pipe fitting, comprising a substrate and an epoxy paint coated on at least a portion of the substrate, wherein the substrate is a cast iron pipe or a cast iron fitting, and the epoxy paint is the epoxy paint described above in the present invention.

[0051] In some specific examples of the present invention, the substrate is a cast iron pipe or cast iron fittings for building drainage.

[0052] In some specific examples of the present invention, the epoxy paint is applied on at least a portion of the substrate to form a coating by the following method:

[0053] The liquid epoxy resin is mixed evenly with a part of the organic solvent and an auxiliary agent containing the thixotropic agent and the pigment and filler wetting and dispersing agent, and then the pigment and filler are added, stirred and dispersed at 2500-3000 rpm for 45-60 minutes, and after uniform dispersion, the mixture is ground to a fineness of ≤45 μm, and then the auxiliary agent containing the defoamer and the adhesion promoter is added, and stirred evenly to obtain a first component;

[0054] The modified polyamide curing agent and the remaining organic solvent are stirred uniformly to obtain a second component;

[0055] The first component and the second component are mixed and stirred evenly, and after adjusting the viscosity of the mixture to reach the required construction viscosity, spraying is performed on the substrate to form a wet film, and then the wet film is baked at 100-130° C. for 20-40 minutes to form a coating; when the coating is an inner coating, the dry film thickness is not less than 120 μm; when the coating is an outer coating, the dry film thickness is not less than 70 μm.

[0056] In the above coating method, the amount of the organic solvent used in the first component and the amount of the organic solvent used in the second component together constitute the total amount of the organic solvent in the epoxy paint: 20.67-34.13%.

[0057] In the above coating method, the viscosity of the mixture can be adjusted by using a small amount of diluent, and the diluent can be one or more of aromatic hydrocarbon, ester, alcohol and ketone solvents.

[0058] The coating formed by the epoxy paint applied on the cast iron pipes or cast iron fittings for building drainage was tested and found to be dense and excellent in performance. The coating performance meets the requirements of the international standard BS EN 877, especially in terms of resistance to hot and cold cycles and salt spray resistance.

[0059] In the present invention, bisphenol A type liquid epoxy resin (especially liquid epoxy resin E51) and specially modified polyamide curing agent are used as the main components of epoxy paint. Since the specially modified polyamide curing agent contains multiple components, it can react with bisphenol A type liquid epoxy resin to form different structures: the chain structure of polyamide and the epoxy resin reactant form a linear network structure with high strength and good flexibility; the polyamide adduct is formed by connecting the flexible polyamide curing agent with the multifunctional glycidyl ether structure to form a multi-branched structure with a functionality of 20 to 30, and after reacting with the epoxy resin, a huge network structure is generated; the reactant of the organic amine with a ring structure and the epoxy resin forms a ring network structure with high rigidity and hardness; the organic amine adduct is formed by connecting the rigid ring structure with the flexible structure. The functionality is 6 to 8, and after reacting with epoxy resin, it forms the main skeleton structure of the cured product and provides high strength. It can be seen that the combination of multi-branched macromolecules and relatively small molecular amines, the combination of flexible segment amines and cyclic amines, gives the specially modified polyamide curing agent and epoxy resin cross-linking and curing to form a coating with special structure and properties: the characteristics of the cyclic structure in the coating are reflected in sufficient hardness, high Tg, and heat resistance; the characteristics of the linear structure in the coating are reflected in sufficient strength and toughness, which can effectively eliminate the internal stress caused by thermal expansion and contraction of the polymer, so that the corresponding coating has high Tg, sufficient strength and toughness. High Tg can increase the curing temperature, and make the paint film have excellent heat resistance and temperature resistance, and even more outstanding temperature change resistance, that is, the paint film has excellent resistance to hot water and resistance to hot and cold alternation. The heat resistance and temperature resistance of the paint film were tested according to the BS EN 877 method, and the results are as follows: hot water (95±2℃), 24h, the paint film has no undesirable phenomena such as shedding, blistering, rusting, etc.; hot and cold water cycle (15±5℃→93±2℃), 1500 times, the paint film has no undesirable phenomena such as shedding, blistering, rusting, etc.

[0060] Relatively speaking, the curing product of epoxy resin and polyamide curing agent in the prior art has a relatively low Tg, and cannot withstand hot water and cold and hot water cycles. As we know, coating failure is generally caused by the penetration of corrosive media (water and oxygen, etc.) into the substrate, corrosion damage to the substrate, blistering, cracking of the coating, or volume expansion caused by rusting of the substrate, which causes the coating to fall off. In the prior art, epoxy coating is a rigid high molecular polymer with low Tg. It cannot complete the yielding effect in time under the stress caused by temperature changes. Under the condition of multiple temperature changes, the coating is damaged and silver streaks are formed, which provides a channel for the penetration of corrosive media. Moreover, epoxy resin and curing agent usually contain a large number of polar groups. After film formation, in addition to the reaction between functional groups, hydrogen bonds will be formed between polar groups to improve the density of the coating. However, if water molecules penetrate, this hydrogen bond will be destroyed and the coating will become loose, the polymer will swell, and the internal free space will become larger, so that water and oxygen will be more easily infiltrated.

[0061] In addition, in the epoxy paint of the present invention, the organic solvent is selected to achieve good solubility of the organic solvent in the epoxy resin, which can effectively improve the dispersion wettability and encapsulation of the pigment filler, effectively adjust the wetting and leveling properties of the substrate and the volatilization gradient of the solvent in the paint film, and form a smooth paint film. At the same time, the selection of pigment fillers and various additives takes into account the mutual coordination of the components in the entire epoxy paint composition, so as to ensure that all performance requirements in the BS EN 877 standard can be met. For example, the selection of non-toxic, harmless and heavy metal-free pigment fillers can meet environmental protection requirements, and the selection of pigments with strong tinting power, good dispersibility and stable chemical structure (such as iron oxide pigments and rutile titanium dioxide) as the main coloring pigment can ensure the color requirements in the BS EN 877 standard; for another example, light-resistant, weather-resistant, chemical-resistant and high-temperature-resistant fillers, especially mica powder with a flaky structure, have good flame retardancy and fire resistance, form a "maze" effect in the paint film, and have a good barrier effect on oxygen and water vapor, so that the coating has excellent shielding and protective properties.

[0062] Moreover, the epoxy paint of the present invention is divided into independently packaged component A and component B in practical application. Under normal construction conditions, one bucket of component A is matched with one bucket of component B. If only a small amount of paint is needed, the paint is matched according to the ratio specified in the composition. The paint matching process ensures the correct percentage of each component contained in the epoxy paint, and also ensures the correct chemical reaction equivalent ratio of epoxy equivalent and amine equivalent, thereby ensuring the quality of the paint film.

[0063] When the epoxy paint of the present invention is used as the anti-corrosion protection of cast iron pipes and cast iron fittings for building drainage, it has a lower film thickness and less usage than general epoxy paints, has lower film-forming energy consumption than epoxy powder coatings, and is easy to repair later. Compared with the prior art, the present invention has at least the following beneficial technical effects, which are specifically described as follows:

[0064] (1) Excellent construction performance: The two liquid components can be applied after being evenly mixed; the mixed viscosity is small, and the paint achieves the best results in terms of atomization, leveling, appearance saturation, paint film coating rate, etc. The paint film is flat and uniform, with no missing spots, and is particularly suitable for the special construction performance of the inner and outer walls of pipeline paint;

[0065] (2) Long mixing pot life: The mixing pot life is not less than 6 hours;

[0066] (3) Good curing and cross-linking performance: the paint film does not soften or re-stick at 100°C;

[0067] (4) Excellent resistance to hot water: No bubbling or other adverse phenomena occur when continuously immersed in hot water of not less than 95°C for 96 hours;

[0068] (5) Excellent resistance to hot and cold water: It has a similar volume change rate to the coated iron substrate under hot and cold alternating environmental conditions, maintaining excellent adhesion. The paint film showed no change after 1500 cycles of alternating hot water (93±2)℃ and cold water (15±5)℃;

[0069] (6) Excellent chemical resistance: not only resistant to domestic sewage, but also has good acid and alkali resistance;

[0070] (7) Good anti-corrosion performance: The paint film can withstand the neutral salt spray test for more than 40 days, meeting the long-term anti-corrosion protection requirements of the building's design service life;

[0071] (8) Low flammability: The paint film has a low organic content and a high inorganic content, and has low flammability, passing the EN 13501-1 combustion level of building products and components. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 A schematic diagram of an above-ground drainage pipe coated with the epoxy paint of the present invention is given.

[0073] Figure 2 A schematic diagram of an above-ground drainage pipe fitting coated with the epoxy paint of the present invention is given.

[0074] Figure 3 A schematic diagram of a drainage pipe coated with the epoxy paint of the present invention for pre-buried underground or for special media requirements is given.

[0075] Figure 4 A schematic diagram of a drainage pipe fitting coated with the epoxy paint of the present invention for pre-buried underground or for special medium requirements is provided.

[0076] Figure 5 Schematic diagram of water flow in a pipe when testing the resistance to hot and cold water cycles according to standard BS EN 877.

[0077] Figure 6 This is a schematic diagram of the drainage pipes in a building. DETAILED DESCRIPTION

[0078] In order to better illustrate the present invention and facilitate understanding of the technical solution of the present invention, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is subject to the claims.

[0079] The reagents and equipment used in the following examples, without specifying the manufacturer, are all conventional products available on the market. The methods used in the following examples, unless otherwise specified, are all conventional methods in the art.

[0080] Liquid epoxy resin E51 was purchased from Jiangsu Sanmu Chemical Co., Ltd. The product brand is SM828, with an effective mass solid content of 100%, an epoxy equivalent of 184-194 g / eq, a viscosity of 11500-15000 CPS / 25°C, and hydrolyzable chlorine ≤1000 ppm.

[0081] Polyamide wax paste, brand MONORAL 3300S, was purchased from MONORAL in Korea.

[0082] Additives Tech-5065 and Tech-367N were purchased from Shanghai Tiger Polymer Technology Co., Ltd.

[0083] Polyamide, Grade 351A, purchased from Air Products & Chemicals, Inc., has an effective mass solid content of 100%, an amine value of 344 mgKOH / g, and an active hydrogen equivalent of 100 Wt%. The glass transition temperature Tg of the polyamide curing agent and the liquid bisphenol A epoxy resin cured at 25°C is 50°C, and the glass transition temperature Tg of the liquid bisphenol A epoxy resin cured at 120°C is 96°C.

[0084] Alicyclic amine curing agent Ancamine TM 2280, purchased from Air Products & Chemicals, Inc., has a mass solid content of 100%, an amine value of 250 mgKOH / g, and an active hydrogen equivalent of 110 Wt%. The glass transition temperature Tg of the alicyclic amine curing agent and the liquid bisphenol A epoxy resin at 25°C is 50°C, and the glass transition temperature Tg of the liquid bisphenol A epoxy resin at 120°C is 125°C.

[0085] Phenolic epoxy resin, brand DEN TM438, purchased from Dow Chemical Company, has an effective mass solid content of 100%, an epoxy equivalent of 176-181 g / eq, and a viscosity of 31000-40000 mPas / 52°C.

[0086] Flexible glycidyl ether, brand name JT-306, was purchased from Shanghai Jingtian New Material Technology Co., Ltd., with an effective mass solid content of 100%, an epoxy equivalent of 410 g / eq, and a viscosity of 200-500 mPas / 25°C.

[0087] In the parameter index test of the modified polyamide curing agent in the following examples, the active hydrogen equivalent is calculated, the mass solid content is measured according to the method of GB / T1725, the amine value is measured by perchloric acid titration, and the Tg of the cured product formed by the curing agent and the epoxy resin at different temperatures is tested according to the method of GB / T 27816-2011.

[0088] Example 1 Red epoxy paint and its application

[0089] An epoxy paint for anticorrosion protection of cast iron pipes and cast iron fittings for building drainage, which has the following composition by mass percentage:

[0090] Liquid epoxy resin E51: 18.5%;

[0091] Organic solvent: 20.7%, including: 1.7% cyclohexanone, 6.4% n-butanol and 12.6% xylene;

[0092] Pigment: 9.1% including: 6.8% iron red, 2.3% iron yellow;

[0093] Filler: 40.8%, including: 35.2% precipitated barium sulfate, 5.6% wet-process mica powder;

[0094] Additives: 2.6%, including: 0.4% additive Tech-5065 (pigment wetting and dispersing agent), 0.9% polyamide wax slurry (thixotropic agent), 0.1% additive Tech-367N (defoaming agent) and 1.2% silane coupling agent A-187 (adhesion promoter);

[0095] Modified polyamide curing agent: 8.3%.

[0096] Wherein, the above-mentioned modified polyamide curing agent is prepared according to the following method:

[0097] Step 1: Add 56 grams of xylene and 24 grams of n-butanol to a four-necked reaction flask containing 400 grams of polyamide, and slowly drip the pre-diluted phenolic epoxy resin liquid (the phenolic epoxy resin liquid is obtained by dissolving 32 grams of phenolic epoxy resin in 55.2 grams of xylene). The dripping temperature is set to 40°C, and cooling begins at the same time, and the temperature is controlled not to exceed 50°C. After the dripping is completed, continue to keep warm for 4 to 6 hours. Finally, heat to 100°C and keep warm for 1 hour. While keeping warm, keep cooling reflux in the condenser to obtain the first mixture.

[0098] Step 2: In a four-necked reaction flask containing 300 g of cyclohexanediamine, 54 g of flexible glycidyl ether is added dropwise, the temperature is set to 30° C., and cooling is started at the same time, and the temperature is controlled not to exceed 40° C. After the addition is completed, the temperature is kept warm for 3 to 4 hours. Then, the temperature is raised to 80° C. and kept warm for 2 hours to obtain a second mixture.

[0099] Step 3: Mix the first mixture and the second mixture in a mass ratio of 100:27, and stir at 50° C. for 1 hour to prepare a modified polyamide curing agent.

[0100] The modified polyamide curing agent obtained above, after testing and calculation, has a mass solid content of 80%, an amine value of 325 mgKOH / g, and an active hydrogen equivalent of 90 Wt%. The glass transition temperature Tg of the modified polyamide curing agent obtained above and the liquid bisphenol A epoxy resin 25°C curing compound is 85°C, the glass transition temperature Tg of the modified polyamide curing agent obtained above and the liquid bisphenol A epoxy resin 60°C curing compound is 102°C, the glass transition temperature Tg of the modified polyamide curing agent obtained above and the liquid bisphenol A epoxy resin 90°C curing compound is 117°C, and the glass transition temperature Tg of the modified polyamide curing agent obtained above and the liquid bisphenol A epoxy resin 130°C curing compound is 125°C.

[0101] The epoxy paint of the above composition is generally separated into two components before use and each is packaged independently, as follows (the following components are all expressed in mass percentage, and the sum of all components is 100%):

[0102] 18.5% liquid epoxy resin E51, 1.7% cyclohexanone, 3.1% n-butanol, 4.2% xylene, 0.4% additive Tech-5065, and 0.9% polyamide wax slurry are mixed and dispersed evenly, and then 6.8% iron oxide red, 2.3% iron oxide yellow, 35.2% precipitated barium sulfate, and 5.6% wet-process mica powder are added and mixed, and dispersed under high-speed stirring at 2500-3000 rpm for 45 minutes, and then ground to a fineness of ≤45 μm, and then 0.1% additive Tech-367N and 1.2% silane coupling agent A-187 (commercially available) are added and stirred evenly to obtain component A.

[0103] 8.3% of modified polyamide curing agent, 8.4% of xylene and 3.3% of n-butanol were stirred evenly to obtain component B.

[0104] The component A and the component B are packaged separately to obtain the anti-corrosion and protective red epoxy paint for cast iron pipes and cast iron accessories for building drainage.

[0105] The epoxy paint of the above composition can be used on cast iron pipes or cast iron fittings for building drainage, as follows:

[0106] Take the independently packaged components A and B in the above epoxy paint, pour the component B into the component A and mix and stir evenly, spray it on the inner / outer surface of the cast iron pipe or cast iron fittings to form a wet film, bake the wet film at 130°C for 30 minutes to form a coating (the inner coating has a dry film thickness of not less than 120μm, and the outer coating has a dry film thickness of not less than 70μm), and obtain a cast iron pipe or cast iron fitting coated with red epoxy paint.

[0107] The above-mentioned spraying can be carried out in different ways according to different construction requirements, and no diluent may be added or a small amount of diluent may be added appropriately. The diluent may generally be an aromatic hydrocarbon, ester, alcohol or ketone solvent.

[0108] The coating obtained above was tested and found to be dense and excellent in performance, not less than the index requirements of standard BS EN 877. The results of the performance test are shown in Table 3 below.

[0109] Example 2 Yellow epoxy paint and its application

[0110] An epoxy paint for anticorrosion protection of cast iron pipes and cast iron fittings for building drainage, which has the following composition by mass percentage:

[0111] Liquid epoxy resin E51: 18.5%;

[0112] Organic solvent: 20.7%, including: 1.7% cyclohexanone, 6.4% n-butanol and 12.6% xylene

[0113] Pigment: 9.1% including: 9.01% iron red, 0.09% iron yellow;

[0114] Filler: 40.8%, including: 35.2% precipitated barium sulfate, 5.6% wet-process mica powder;

[0115] Additives: 2.6%, including: 0.4% additive Tech-5065 (pigment wetting and dispersing agent), 0.9% polyamide wax slurry (thixotropic agent), 0.1% additive Tech-367N (defoaming agent) and 1.2% silane coupling agent A-187 (adhesion promoter);

[0116] Modified polyamide curing agent: 8.3%.

[0117] Wherein, the above-mentioned modified polyamide curing agent is prepared according to the following method:

[0118] Step 1: Add 56 grams of xylene and 24 grams of n-butanol to a four-necked reaction flask containing 400 grams of polyamide, and slowly drip the pre-diluted phenolic epoxy resin liquid (the phenolic epoxy resin liquid is obtained by dissolving 32 grams of phenolic epoxy resin in 55.2 grams of xylene). The dripping temperature is set to 40°C, and cooling begins at the same time, and the temperature is controlled not to exceed 50°C. After the dripping is completed, continue to keep warm for 4 to 6 hours. Finally, heat to 100°C and keep warm for 1 hour. While keeping warm, keep cooling reflux in the condenser to obtain the first mixture.

[0119] Step 2: In a four-necked reaction flask containing 300 g of cyclohexanediamine, 54 g of flexible glycidyl ether is added dropwise, the temperature is set to 30° C., and cooling is started at the same time, and the temperature is controlled not to exceed 40° C. After the addition is completed, the temperature is kept warm for 3 to 4 hours. Then, the temperature is raised to 80° C. and kept warm for 2 hours to obtain a second mixture.

[0120] Step 3: Mix the first mixture and the second mixture in a mass ratio of 100:27, and stir at 50° C. for 1 hour to prepare a modified polyamide curing agent.

[0121] The modified polyamide curing agent obtained above, after testing and calculation, has a mass solid content of 80%, an amine value of 325 mgKOH / g, and an active hydrogen equivalent of 90 Wt%. The glass transition temperature Tg of the modified polyamide curing agent obtained above and the liquid bisphenol A epoxy resin 25°C curing compound is 85°C, the glass transition temperature Tg of the modified polyamide curing agent obtained above and the liquid bisphenol A epoxy resin 60°C curing compound is 102°C, the glass transition temperature Tg of the modified polyamide curing agent obtained above and the liquid bisphenol A epoxy resin 90°C curing compound is 117°C, and the glass transition temperature Tg of the modified polyamide curing agent obtained above and the liquid bisphenol A epoxy resin 130°C curing compound is 125°C.

[0122] The epoxy paint of the above composition is generally separated into two components before use and each is packaged independently, as follows (the following components are all expressed in mass percentage, and the sum of all components is 100%):

[0123] 18.5% liquid epoxy resin E51, 1.7% cyclohexanone, 3.1% n-butanol, 4.2% xylene, 0.4% additive Tech-5065, and 0.9% polyamide wax slurry were mixed and dispersed evenly, and then 9.01% iron oxide red, 0.09% iron oxide yellow, 35.2% precipitated barium sulfate, and 5.6% wet-process mica powder were added and mixed, and dispersed for 45 minutes under high-speed stirring at 2500-3000 rpm, and then ground to a fineness of ≤45 μm, and then 0.1% additive Tech-367N and 1.2% silane coupling agent A-187 were added and stirred evenly to obtain component A.

[0124] 8.3% of modified polyamide curing agent, 8.4% of xylene and 3.3% of n-butanol were stirred evenly to obtain component B.

[0125] The component A and the component B are packaged separately to obtain the yellow epoxy paint for anti-corrosion protection of cast iron pipes and cast iron accessories for building drainage.

[0126] The epoxy paint of the above composition can be used on cast iron pipes or cast iron fittings for building drainage, as follows:

[0127] Take the independently packaged components A and B in the above epoxy paint, pour the component B into the component A and mix and stir evenly, spray it on the inner / outer surface of the cast iron pipe or cast iron fittings to form a wet film, bake the wet film at 130°C for 30 minutes to form a coating (the inner coating has a dry film thickness of not less than 120μm, and the outer coating has a dry film thickness of not less than 70μm), and obtain a cast iron pipe or cast iron fittings coated with yellow epoxy paint.

[0128] The above-mentioned spraying can be carried out in different ways according to different construction requirements, and no diluent may be added or a small amount of diluent may be added appropriately. The diluent may generally be an aromatic hydrocarbon, ester, alcohol or ketone solvent.

[0129] The coating obtained above was tested and found to be dense and excellent in performance, not less than the index requirements of standard BS EN 877. The results of the performance test are shown in Table 3 below.

[0130] Example 3 Grey epoxy paint and its application

[0131] An epoxy paint for anticorrosion protection of cast iron pipes and cast iron fittings for building drainage, which has the following composition by mass percentage:

[0132] Liquid epoxy resin E51: 13.92%;

[0133] Organic solvent: 23.64%, including: 2.36% cyclohexanone, 4.74% n-butanol, 4.79% trimethylol solvent oil (also known as 100# solvent oil) and 11.75% xylene;

[0134] Pigments: 12.62% including: 12.50% rutile titanium dioxide, 0.12% carbon black;

[0135] Filler: 40.18%, including: 33.30% precipitated barium sulfate, 6.88% wet-process mica powder;

[0136] Additives: 3.16%, including: 0.52% additive Tech-5065 (pigment wetting and dispersing agent), 0.94% polyamide wax slurry (thixotropic agent), 0.20% additive Tech-367N (defoaming agent) and 1.50% silane coupling agent A-187 (adhesion promoter);

[0137] Modified polyamide curing agent: 6.48%.

[0138] Wherein, the above-mentioned modified polyamide curing agent is prepared according to the following method:

[0139] Step 1: Add 56 grams of xylene and 24 grams of n-butanol to a four-necked reaction flask containing 400 grams of polyamide, and slowly drip the pre-diluted phenolic epoxy resin liquid (the phenolic epoxy resin liquid is obtained by dissolving 32 grams of phenolic epoxy resin in 55.2 grams of xylene). The dripping temperature is set to 40°C, and cooling begins at the same time, and the temperature is controlled not to exceed 50°C. After the dripping is completed, continue to keep warm for 4 to 6 hours. Finally, heat to 100°C and keep warm for 1 hour. While keeping warm, keep cooling reflux in the condenser to obtain the first mixture.

[0140] Step 2: In a four-necked reaction flask containing 300 g of cyclohexanediamine, 54 g of flexible glycidyl ether is added dropwise, the temperature is set to 30° C., and cooling is started at the same time, and the temperature is controlled not to exceed 40° C. After the addition is completed, the temperature is kept warm for 3 to 4 hours. Then, the temperature is raised to 80° C. and kept warm for 2 hours to obtain a second mixture.

[0141] Step 3: Mix the first mixture and the second mixture in a mass ratio of 100:27, and stir at 50° C. for 1 hour to prepare a modified polyamide curing agent.

[0142] The modified polyamide curing agent obtained above, after testing and calculation, has a mass solid content of 80%, an amine value of 325 mgKOH / g, and an active hydrogen equivalent of 90 Wt%. The glass transition temperature Tg of the modified polyamide curing agent obtained above and the liquid bisphenol A epoxy resin 25°C curing compound is 85°C, the glass transition temperature Tg of the modified polyamide curing agent obtained above and the liquid bisphenol A epoxy resin 60°C curing compound is 102°C, the glass transition temperature Tg of the modified polyamide curing agent obtained above and the liquid bisphenol A epoxy resin 90°C curing compound is 117°C, and the glass transition temperature Tg of the modified polyamide curing agent obtained above and the liquid bisphenol A epoxy resin 130°C curing compound is 125°C.

[0143] The epoxy paint of the above composition is generally separated into two components before use and each is packaged independently, as follows (the following components are all expressed in mass percentage, and the sum of all components is 100%):

[0144] 13.92% of liquid epoxy resin E51, 2.36% of cyclohexanone, 3.82% of n-butanol, 4.79% of 100# solvent oil, 10.05% of xylene, 0.52% of auxiliary agent Tech-5065, and 0.94% of polyamide wax slurry were mixed and dispersed evenly, and then 12.50% of rutile titanium dioxide, 0.12% of carbon black, 33.3% of precipitated barium sulfate, and 6.88% of wet-process mica powder were added and mixed, and dispersed for 45 minutes under high-speed stirring at 2500-3000 rpm, and then ground to a fineness of ≤45 μm, and then 0.20% of auxiliary agent Tech-367N and 1.50% of silane coupling agent A-187 were added and stirred evenly to obtain component A.

[0145] 6.48% of modified polyamide curing agent, 1.70% of xylene and 0.92% of n-butanol were stirred evenly to obtain component B.

[0146] The component A and the component B are packaged separately to obtain the anti-corrosion protective grey epoxy paint for cast iron pipes and cast iron fittings for building drainage.

[0147] The epoxy paint of the above composition can be used on cast iron pipes or cast iron fittings for building drainage, as follows:

[0148] Take the independently packaged components A and B in the above epoxy paint, pour the component B into the component A and mix and stir evenly, spray it on the inner / outer surface of the cast iron pipe or cast iron fittings to form a wet film, bake the wet film at 130°C for 30 minutes to form a coating (the inner coating has a dry film thickness of not less than 120μm, and the outer coating has a dry film thickness of not less than 70μm), and obtain a cast iron pipe or cast iron fitting coated with gray epoxy paint.

[0149] The above-mentioned spraying can be carried out in different ways according to different construction requirements, and no diluent may be added or a small amount of diluent may be added appropriately. The diluent may generally be an aromatic hydrocarbon, ester, alcohol or ketone solvent.

[0150] The coating obtained above was tested and found to be dense and excellent in performance, not less than the index requirements of standard BS EN 877. The results of the performance test are shown in Table 3 below.

[0151] Figure 1 A schematic diagram of an above-ground drainage pipe coated with the epoxy paint of the present invention is given, wherein an epoxy paint outer coating 1 and an epoxy paint inner coating 3 are formed on the inner wall and outer wall of an iron substrate 2 of the drainage pipe, respectively, wherein the outer coating 1 is red epoxy paint and the inner coating 3 is yellow epoxy paint.

[0152] Figure 2 A schematic diagram of an above-ground drainage pipe fitting coated with the epoxy paint of the present invention is given, wherein an epoxy paint outer coating 1 and an epoxy paint inner coating 3 are formed on the inner wall and outer wall of the iron substrate 2 of the drainage pipe fitting, wherein the outer coating 1 and the inner coating 3 are both red epoxy paints.

[0153] Figure 3 A schematic diagram of a drainage pipe coated with the epoxy paint of the present invention for pre-buried underground or for special media requirements is given, wherein an epoxy paint outer coating 1 and an epoxy paint inner coating 3 are formed on the inner wall and outer wall of the iron substrate 2 of the drainage pipe fitting, wherein the outer coating 1 is gray epoxy paint and the inner coating 3 is yellow epoxy paint.

[0154] Figure 4 A schematic diagram of a drainage pipe fitting coated with the epoxy paint of the present invention for pre-buried underground or for special media requirements is given, wherein an epoxy paint outer coating 1 and an epoxy paint inner coating 3 are formed on the inner wall and outer wall of the iron substrate 2 of the drainage pipe fitting, wherein the outer coating 1 and the inner coating 3 are both gray epoxy paints.

[0155] The schematic diagram of the pipelines of various drainage pipes and accessories in the building is as follows Figure 6 shown.

[0156] Comparative Example 1

[0157] An epoxy paint for anticorrosion protection of cast iron pipes and cast iron fittings for building drainage, which has the following composition by mass percentage:

[0158] Liquid epoxy resin E51: 18.5%;

[0159] Organic solvent: 19.5%, including: 1.7% cyclohexanone, 6.4% n-butanol, and 11.4% xylene;

[0160] Pigment: 9.1% including: 6.8% iron red, 2.3% iron yellow;

[0161] Filler: 40.8%, including: 35.2% precipitated barium sulfate, 5.6% wet-process mica powder;

[0162] Additives: 2.6%, including: 0.4% additive Tech-5065 (pigment wetting and dispersing agent), 0.9% polyamide wax slurry (thixotropic agent), 0.1% additive Tech-367N (defoaming agent) and 1.2% silane coupling agent A-187 (adhesion promoter);

[0163] Polyamide curing agent Ancamide 351A: 9.5%.

[0164] The epoxy paint of the above composition is generally separated into two components before use and each is packaged independently, as follows (the following components are all expressed in mass percentage, and the sum of all components is 100%):

[0165] 18.5% liquid epoxy resin E51, 1.7% cyclohexanone, 3.1% n-butanol, 4.2% xylene, 0.4% additive Tech-5065 (dispersant), and 0.9% polyamide wax slurry (thixotropic agent) are mixed and dispersed evenly, and then 6.8% iron oxide red, 2.3% iron oxide yellow, 35.2% precipitated barium sulfate, and 5.6% wet-process mica powder are added and mixed, and dispersed at a high-speed stirring of 2500 to 3000 rpm for 45 minutes, and then ground to a fineness of ≤45 μm, and then 0.1% additive Tech-367N (defoaming agent) and 1.2% silane coupling agent A-187 (adhesion promoter) are added and stirred evenly to obtain component A.

[0166] 9.5% polyamide curing agent Ancamide 351A, 7.2% xylene, and 3.3% n-butanol were stirred evenly to obtain component B.

[0167] The component A and the component B are packaged separately to obtain the anti-corrosion red epoxy paint for cast iron pipes and cast iron accessories for building drainage.

[0168] The epoxy paint of the above composition can be used on cast iron pipes or cast iron fittings for building drainage, as follows:

[0169] Take the independently packaged components A and B in the above epoxy paint, pour component B into component A and mix and stir evenly, spray on the inner / outer surface of the cast iron pipe and cast iron fittings to form a wet film, bake the wet film at 130°C for 30 minutes to form a coating (the inner coating has a dry film thickness of not less than 120μm, and the outer coating has a dry film thickness of not less than 70μm), and obtain cast iron pipes and cast iron fittings coated with red epoxy paint.

[0170] The above-mentioned spraying can be carried out in different ways according to different construction requirements, and no diluent may be added or a small amount of diluent may be added appropriately.

[0171] The coating obtained above was tested in accordance with the requirements of standard BS EN 877. The results of the performance test are shown in Table 3 below.

[0172] Comparative Example 2

[0173] An epoxy paint for anticorrosion protection of cast iron pipes and cast iron fittings for building drainage, which has the following composition by mass percentage:

[0174] Liquid epoxy resin E51: 18.5%;

[0175] Organic solvent: 18.6%, including: 1.7% cyclohexanone, 6.4% n-butanol, and 10.5% xylene;

[0176] Pigment: 9.1% including: 6.8% iron red, 2.3% iron yellow;

[0177] Filler: 40.8%, including: 35.2% precipitated barium sulfate, 5.6% wet-process mica powder;

[0178] Additives: 2.6%, including: 0.4% additive Tech-5065 (pigment wetting and dispersing agent), 0.9% polyamide wax slurry (thixotropic agent), 0.1% additive Tech-367N (defoaming agent) and 1.2% silane coupling agent A-187 (adhesion promoter);

[0179] Alicyclic amine curing agent Ancamine TM 2280:10.4%.

[0180] The epoxy paint of the above composition is generally separated into two components before use and each is packaged independently, as follows (the following components are all expressed in mass percentage, and the sum of all components is 100%):

[0181] 18.5% liquid epoxy resin E51, 1.7% cyclohexanone, 3.1% n-butanol, 4.2% xylene, 0.4% additive Tech-5065 (dispersant), and 0.9% polyamide wax slurry (thixotropic agent) are mixed and dispersed evenly, and then 6.8% iron oxide red, 2.3% iron oxide yellow, 35.2% precipitated barium sulfate, and 5.6% wet-process mica powder are added and mixed, and dispersed at a high-speed stirring of 2500 to 3000 rpm for 45 minutes, and then ground to a fineness of ≤45 μm, and then 0.1% additive Tech-367N (defoaming agent) and 1.2% silane coupling agent A-187 (adhesion promoter) are added and stirred evenly to obtain component A.

[0182] 10.4% of alicyclic amine curing agent AncamineTM2280, 6.3% of xylene, and 3.3% of n-butanol were stirred evenly to obtain component B.

[0183] The component A and the component B are packaged separately to obtain the anti-corrosion red epoxy paint for cast iron pipes and cast iron accessories for building drainage.

[0184] The epoxy paint of the above composition can be used on cast iron pipes or cast iron fittings for building drainage, as follows:

[0185] Take the independently packaged components A and B in the above epoxy paint, pour component B into component A and mix and stir evenly, spray on the inner / outer surface of the cast iron pipe and cast iron fittings to form a wet film, bake the wet film at 130°C for 30 minutes to form a coating (the inner coating has a dry film thickness of not less than 120μm, and the outer coating has a dry film thickness of not less than 70μm), and obtain cast iron pipes and cast iron fittings coated with red epoxy paint.

[0186] The above-mentioned spraying can be carried out in different ways according to different construction requirements, and no diluent may be added or a small amount of diluent may be added appropriately.

[0187] The coating obtained above was tested in accordance with the requirements of standard BS EN 877. The results of the performance test are shown in Table 3 below.

[0188] Performance Testing

[0189] The technical indicators and test methods for internal and external coatings in the standard BS EN 877 "Requirements, test methods and quality assurance for cast iron pipes and fittings for drainage in buildings and their connections and accessories" are shown in Table 1 and Table 2 respectively:

[0190] Table 1 Technical indicators and test methods for internal coatings of building drainage pipes

[0191]

[0192] Production conditions of samples 1-8: cast iron pipes for building drainage, specifications: After one spraying, the paint film thickness is 120-400μm and baked at 130℃ for 30min.

[0193] Item 3: If the dry film thickness is ≤120μm, the cross-cut width is 2mm; if the dry film thickness is greater than 120μm, the cross-cut width is 3mm.

[0194] Item 5: Preparation method for every 1L of wastewater: 50mg starch, 32mg sodium stearate, 56mg sodium acetate, 15mg tristearin, 13mg urea, 70mg ammonium sulfate, 90mg protein and appropriate amount of drinking water.

[0195] Item 8: Hot water (93±2)℃ flows into the pipe at a certain flow rate for 1 minute, and then the water is drained out in 1 minute. Then cold water (15±5)℃ flows into the pipe at a certain flow rate for 1 minute, and then the water is drained out in 1 minute. This cycle repeats. Figure 5 shown. Figure 5 In the diagram, 1 represents flow direction, 2 represents pipes, 3 represents elbow fittings, and 4 represents joints.

[0196] Table 2 Technical indicators and test methods for external coatings of building drainage pipes

[0197]

[0198] Production conditions for samples 1-6: cast iron pipes for building drainage, specifications: φ50-150mm; one coat of spraying, paint film thickness ≥70μm, baked at 130℃ for 30min.

[0199] Item 4: If the dry film thickness is ≤120μm, the cross-cut width is 2mm; if the dry film thickness is greater than 120μm, the cross-cut width is 3mm.

[0200] Item 5: Apply one layer of alkyd paint and one layer of water-based acrylic emulsion anti-rust paint respectively, with the film thickness of (50±10)μm. After curing for 7 days, test according to the requirements of Item 4.

[0201] Note: There are color requirements (L=37; a=24; b=16), which are only limited to the outer coating of the ground drainage pipes in the building.

[0202] According to the technical indicators and test methods of the internal and external coatings in the standard BS EN 877 "Requirements, test methods and quality assurance of cast iron pipes and fittings and their connectors and accessories for drainage in buildings", the coatings / paint films of the pipes obtained in Examples 1 to 3 and Comparative Examples 1 to 2 were tested, and the results are shown in Table 3 below:

[0203] Table 3 Results of performance tests of the examples and comparative examples according to BS EN 877

[0204]

[0205] It can be seen from Table 3 that the coating formed on the cast iron pipe or cast iron fittings by the epoxy paint of Examples 1 to 3 of the present invention meets the BS EN 877 standard. The coating formed on the cast iron pipe or cast iron fittings by the epoxy paint of Comparative Examples 1 and 2 does not fully meet the BS EN 877 standard. For example, Comparative Example 1 does not meet the requirements of the BS EN 877 standard in terms of hot water resistance and cold and hot water cycle resistance, and Comparative Example 2 does not meet the requirements of the BS EN 877 standard in terms of salt spray resistance. It can be seen that, compared with the coatings formed on Comparative Examples 1 and 2, the coatings formed on the cast iron pipe or cast iron fittings by the epoxy paint of Examples 1 to 3 of the present invention have outstanding performance in terms of hot water resistance, cold and hot water alternating cycle resistance and salt spray resistance.

[0206] In addition, the epoxy paint of the present invention is divided into independently packaged component A and component B in actual application. Under normal construction conditions, one bucket of component A is matched with one bucket of component B. If only a small amount of paint is needed, it is only necessary to match the paint according to the ratio specified in the composition. The paint matching process ensures the correct percentage of each component contained in the epoxy paint, and also ensures the correct chemical reaction equivalent ratio of epoxy equivalent and amine equivalent, thereby ensuring the quality of the paint film. When the epoxy paint of the present invention is used as the anti-corrosion protection of cast iron pipes and cast iron accessories for building drainage, it has a lower film thickness than general epoxy paint, less usage, lower film-forming energy consumption than epoxy powder coating, and is easy to repair later. In addition, the epoxy paint of the present invention also has the following advantages:

[0207] (1) Excellent construction performance: The two liquid components can be applied after being evenly mixed; the mixed viscosity is small, and the paint achieves the best results in terms of atomization, leveling, appearance saturation, paint film coating rate, etc. The paint film is flat and uniform, with no missing spots, and is particularly suitable for the special construction performance of the inner and outer walls of pipeline paint;

[0208] (2) Long mixing pot life: The mixing pot life is not less than 6 hours;

[0209] (3) Good curing and cross-linking performance: the paint film does not soften or re-stick at 100°C;

[0210] (4) Excellent resistance to hot water: No bubbling or other adverse phenomena occur when continuously immersed in hot water of not less than 95°C for 96 hours;

[0211] (5) Excellent resistance to hot and cold water: It has a similar volume change rate to the coated iron substrate under hot and cold alternating environmental conditions, maintaining excellent adhesion. The paint film showed no change after 1500 cycles of alternating hot water (93±2)℃ and cold water (15±5)℃;

[0212] (6) Excellent chemical resistance: not only resistant to domestic sewage, but also has good acid and alkali resistance;

[0213] (7) Good anti-corrosion performance: The paint film can withstand the neutral salt spray test for more than 40 days, meeting the long-term anti-corrosion protection requirements of the building's design service life;

[0214] (8) Low flammability: The paint film has a low organic content and a high inorganic content, and has low flammability, passing the EN 13501-1 combustion level of building products and components.

[0215] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention is described by reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. An epoxy paint, characterized in that: The composition comprises a liquid epoxy resin and a modified polyamide curing agent, wherein the modified polyamide curing agent is obtained by uniformly mixing a first mixture and a second mixture in proportion; wherein the first mixture is a mixture of polyamide and a polyamide adduct, wherein the polyamide adduct is obtained by an addition reaction between the polyamide and a multifunctional glycidyl ether; and the second mixture is a mixture of an organic amine having a cyclic structure and an organic amine adduct, wherein the organic amine adduct is obtained by an addition reaction between the organic amine having a cyclic structure and a flexible glycidyl ether; Wherein, the functionality of the polyamide adduct is 20-30, and the functionality of the organic amine adduct is 6-8.

2. The epoxy paint according to claim 1, characterized in that The modified polyamide curing agent is prepared by the following method: (1) Add 56 g of xylene and 24 g of n-butanol to a reaction vessel containing 400 g of polyamide, control the temperature at 40° C. to 50° C., and then slowly dropwise add a phenolic epoxy resin liquid, the phenolic epoxy resin liquid being composed of 55.2 g of xylene and 32 g of phenolic epoxy resin DEN TM 438, and continue to keep the temperature for 4 to 6 hours after the dropwise addition is completed; then, raise the temperature to 100° C. and keep the temperature for 1 hour to obtain a first mixture; (2) adding 54 g of flexible glycidyl ether dropwise to a reaction vessel containing 300 g of cyclohexanediamine, controlling the temperature at 30° C. to 40° C., and keeping the temperature for 3 to 4 hours after the addition is complete, then raising the temperature to 80° C. and keeping the temperature for 2 hours to obtain a second mixture; (3) The first mixture and the second mixture were mixed at a mass ratio of 100:27, and stirred at 50° C. for 1 hour to obtain the modified polyamide curing agent.

3. The epoxy paint according to claim 1, characterized in that The liquid epoxy resin is bisphenol A type liquid epoxy resin.

4. The epoxy paint according to any one of claims 1 to 3, characterized in that In terms of mass percentage, its composition includes: Liquid epoxy resin: 13.19-23.45%; Organic solvents: 20.67-34.13%; Pigments, including: iron oxide pigments 0-11.37%, rutile titanium dioxide 0-12.55%, carbon black 0-0.42%; Filler, including: 20.08-37.24% of precipitated barium sulfate and 4.52-7.04% of wet-process mica powder; Additives: 2.43-4.22%; Modified polyamide: 5.17-10.46%; The sum of all components in the epoxy paint is 100%.

5. The epoxy paint as claimed in claim 4, characterized in that The organic solvent includes one or more of benzene, alcohol and ketone organic solvents.

6. The epoxy paint as claimed in claim 4, characterized in that The auxiliary agent includes one or more of a thixotropic agent, a pigment and filler wetting and dispersing agent, a defoaming agent and an adhesion promoter.

7. The epoxy paint as claimed in claim 4, characterized in that The auxiliary agent includes a thixotropic agent, a pigment and filler wetting and dispersing agent, a defoaming agent and an adhesion promoter.

8. A coated pipe fitting comprising a substrate and an epoxy paint coated on at least a portion of the substrate, wherein the substrate is a cast iron pipe or a cast iron fitting, characterized in that: The epoxy paint is the epoxy paint according to any one of claims 1 to 7.

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