3급 아민을 포함하는 만니히형 反應性 添加劑 樹脂를 含有한 2액형 에폭시계 防蝕塗料에 대한 硏究

Abstract

At the moment, marine coating is one of the most well-known ‘Protective Coatings & Anticorrosive Coatings’. If we are to define protective coatings, it can be simply put as the coatings that protect coated materials from various corrosive factors and set conditions to perform its function for certain period of time. Of course, capricious environment that surrounds the coated material should be closely monitored upon selection and application of protective coatings. Marine structures and vessels are always exposed to highly corrosive environments including the seawater. Therefore, in addition to basic function of coated film itself, coatings used for the above structures must be equipped with anticorrosive property in various marine environments. Among all protective coatings, epoxy paint is most widely used for its excellent physical and chemical properties and the fact that it is easy to modify or reprocess to various functions and usages. Unlike a wide array of advantage, when some epoxy binder systems are applied under low temperature and/or high humidity conditions, a side effect(Blushing and Blooming) of the curing reaction may appear on the coating or coating surface. In some instances it may not be visible. Although the exudate is, in principle, water soluble it will in most cases not wipe off easily with water, thinners or solvents. Often it can only be removed by dry or wet sanding after the binder has completely cured. Blushing and blooming are surface defects that need to be removed from an epoxy coating. They affect the coating performance as they can result in poor gloss retention, discoloration over time (yellowing), poor overcoatability and intercoat adhesion. The most important of these effects is the reduced overcoatability. As the temperature decreases the reaction rate of the amine and epoxy resin is significantly decreased. For every 10°C reduction in curing temperature the reaction rate will be reduced by a factor of approximately 2. The reduction of the cure speed of the epoxy-amine reaction leaves the (primary-) amines more time to migrate to the surface and undergo alternative reactions. If, during this period, the environment is damp and cold, the reaction of the amine with CO2 and water is favored resulting in the formation of blush and bloom. In order to eliminate the formation of blush or bloom, a wide range of modified amine curing agents have been developed. The two major categories are epoxy-amide adduct hardeners and a special form of adduct hardeners: Mannich-bases Polyamine. The epoxy-amide adduct curing agents are the largest category of products designed to have a reduced tendency to blush. Epoxy-amine adducts are reaction products of liquid epoxy resin with an excess of primary amines. Although epoxy amine adducts still contain a large excess of free amine they are less hygroscopic and have a lower vapor pressure compared to the neat amines. Epoxy-amide adducts are less sensitive to blush formation and as a result are better suited for coatings which cure under high humidity / low temperature. A disadvantage of epoxy-amine adducts is their relatively high viscosity. In order to reduce the viscosity epoxy-amine adducts are often modified with solvents or plasticizers, a common example of such is for instance benzyl alcohol. Mannich-base Polyamine curing agents are adduct type hardeners formed by the condensation of (aliphatic-) amines, phenol (derivatives) and formaldehyde. The phenolic hydroxyl group present in these types of molecules has an accelerating effect on the epoxy amine reaction rate. Moreover, Mannich-bases show better compatibility with liquid epoxy resins than unmodified alkylene amines, reduced blush/bloom tendency and improved early water spot resistance. These products increase the epoxy amine reaction rate and subsequently reduce the possibility of the undesired blushing or blooming reactions. Controlled use of the amount and type of accelerator ensures minimal impact on the cured binder performance. Although there are numerous products capable of accelerating amine-epoxy reactions, the most commonly used are: tertiary-amines (e.g. DMP-30 = 2,4,6-Tris-[Dimethylamin -omethyl]-phenol). The main purpose of this study is to apply a co-reacting accelerator resin containing a tertiary amine derived mannich base as a accelerator and prove their performances in high solid epoxy coatings, which can help to optimize the properties of the high solid anti-corrosive coatings. In this study, a high solid epoxy coating, 80% SVR(Solid Volume Content), was formulated based on commercial epoxy resin system, DGEBA - Bisphenol A Type epoxy and Modified aliphatic polyamide amine, and 2 kinds of accelerator resin containing a tertiary amine, which have different molecular structure and characteristic, were added by 5%wt to evaluate their application and performance in the coatings. The specimens were produced by applying 3 kinds of the 80% solid epoxy coatings. DSC Analysis and Rheovibron(Rigid-Body Pendulum Type Physical Properies Test Instrument) were carried out as an assessment of curing speed and cross-linking density of anticorrosive coatings. The creepage analysis was conducted to verify the corrosion as a result of accelerated aging tests(IMO PSPC Resolution 215(82), 288(87), NORSOK M501 test and Wet adhesion test) were also carried out.

In the results of test, The test formulation comprising the co-react -ing accelerator resin containing a tertiary amine derived mannich base applied high solid epoxy coating had good performances in the accelerated aging test condition and improve physical properties in comparison with a control group.