How to prevent agglomeration of powder coating

Powder coatings tend to agglomerate at a certain temperature, which is mainly caused by the softening of resin, leveling agent and other materials The powder coatings produced by our company are all thermosetting powder coatings, that is to say, the resin as the main film-forming material is the organic polymer with low molecular weight These resins have a kind of physical properties At a lower temperature, they show a hard and brittle glass state When the temperature rises to a certain degree, the resin begins to change into a state with certain elasticity and generate adhesion Below this temperature, the resin returns to a non adhesion glass state The temperature at which the glass state and viscoelastic state of the resin change each other is called the glass transition temperature of the resin Degree Different resins have different glass transition temperatures For example, the glass transition temperature of epoxy resin and polyester resin is about 50 ℃, the glass transition temperature of brightener (701) is about 30 ℃, and the glass transition temperature of liquid leveling agent is about 0 ℃ The larger the amount of materials with low glass transition temperature is, the lower the glass transition temperature is To determine the glass transition temperature, we need to have special large-scale instruments General powder coating manufacturers do not have such expensive instruments and equipment We cannot grasp the glass transition temperature of the powder system in time during the production process Therefore, the glass transition temperature of the powder system is located at about 40 ° C during the production, which is the safe temperature for powder coating agglomeration Then in the production (as well as product storage and transportation process) as a standard, when the temperature is close to or higher than this, relevant personnel should strengthen the sampling inspection of product caking At present, it has entered the summer production stage, and the rise of temperature will make it easier for the agglomeration of powder coating products So how to prevent the agglomeration of powder coating in the work? First of all, we should establish a concept: the agglomeration of powder coating at a certain temperature is a natural law In order to prevent the agglomeration of powder coating, the powder coating product must be below its glass transition temperature in the whole process of grinding, packaging, storage, transportation, etc According to this point of view, there are the following solutions: 1) in the production of polyester resin, select some alcohol or acid that can improve its glass transition temperature, or reduce the amount of alcohol that can reduce the glass transition temperature of resin to improve the glass transition temperature of polyester resin 2) in the formulation design of powder coating, reduce the use of low glass transition temperature polymer, such as leveling agent and brightener, to ensure that the glass transition temperature of powder coating system will not be reduced 3) in terms of production, the broken pieces on and off the steel belt shall be fully cooled before entering the grinding process When grinding, the feeding speed shall be properly reduced, the air volume of induced air shall be increased, and the air conditioner shall be installed on the inlet air to control the grinding temperature However, if the cooling of the crushed pieces can not be achieved before grinding, the latter means will not play a good role It can be considered that the method of forced cooling of the crushed pieces can be used for low-temperature treatment, which is more effective than adding air conditioning In addition, anti caking additives, such as nano silica (vk-sp15) or nano aluminum oxide (vk-l20m) powder, can be added to prevent adhesion between powder particles Generally, anti caking agent and broken sheet material have the best grinding effect at the same time The application scope of nanometer aluminum oxide (vk-l20m) and nanometer silicon dioxide (vk-sp15): 1 Thermosetting powder coating: epoxy resin system, polyester system and acrylic resin system For example, epoxy powder coating, polyester powder coating, acrylate powder coating, etc 2 Thermoplastic powder coating: thermoplastic powder coating includes polyethylene, polypropylene, polyester, PVC, chlorinated polyether, polyamide, cellulose and polyester For example, polyvinyl chloride powder coating, polyethylene powder coating, nylon powder coating, fluororesin powder coating, latex powder coating and other nano aluminum oxide (vk-l20m) use characteristics: nano aluminum oxide (vk-l20m) used in powder coating can improve the fluffy degree of powder coating, with good anti caking effect For the powder coating used in high temperature and high humidity environment, it has good storage The addition amount is generally 0.2-0.5% Nano-Al2O3 can improve the charged property of the powder, especially when friction charged spraying is used, it can obviously improve the powder loading rate and solve the problem of dead angle, and has no effect on the glossiness of the powder coating Using any single method can not effectively prevent the agglomeration of powder coating Overusing one method will bring other disadvantages to powder coating Only scientific cooperation with many methods can effectively prevent the agglomeration of powder coating.