Synthetic resins are synthetic polymers with some properties similar to natural resins. They usually have a certain melting or softening temperature range and can exhibit a plastic flow state under the action of external forces. Synthetic resins can be divided into two categories: additive resins and polycondensation resins, and can also be divided into thermoplastic resins and thermosetting resins according to their properties.
Features
Synthetic resins used in coating preparation must have the following characteristics:
Good solubility and dispersibility, can be uniformly dispersed in the dispersion medium.
It has excellent film-forming properties, can form coating films, and has specific coating properties, such as gloss, hardness, elasticity, weather resistance and corrosion resistance.
It can effectively wet the pigment and ensure that the pigment is evenly dispersed in the paint.
It has good storage stability to ensure that the paint does not delaminate or deteriorate during storage.
Coatings with synthetic resin as the main film-forming material are usually superior to oil coatings and natural resin coatings in terms of mechanical properties, decorative properties and protective properties.
Method
In the preparation of synthetic resins, there are four commonly used methods, which are bulk polymerization, suspension polymerization, emulsion polymerization and solution polymerization.
bulk polymerization
Bulk polymerization, also known as bulk polymerization, is a method of preparing synthetic resins by polymerizing monomers under the action of an initiator or heat, light, and radiation. The advantages of this method are that the product is pure, does not require complicated separation and purification steps, and is relatively simple to operate. However, the viscosity of the material during bulk polymerization increases as the polymerization reaction progresses, which can lead to difficulties in mixing and heat transfer, while also making the reactor temperature difficult to control. This method is commonly used to produce resins such as polymethyl methacrylate, polystyrene, polyester, and polyamide.
Suspension polymerization
Suspension polymerization, also known as bead polymerization, is a method of polymerization by dispersing monomers into droplets and suspending them in water under the action of mechanical stirring or shaking and a dispersant. After polymerization, the resin can be obtained through simple separation, washing and drying steps, and the product is relatively pure and uniform. However, the product of suspension polymerization is slightly less pure than bulk polymerization.
Emulsion polymerization
The emulsion polymerization method utilizes the action of an emulsifier. Under mechanical stirring or shaking, the monomers are dispersed in water to form an emulsion, and then polymerized. The product is latex, which can be applied directly or can be post-treated to obtain powdery or needle-like polymers. This method can obtain high molecular weight polymers at higher reaction rates and easily remove residual monomers. However, the process of removing the emulsifier is complicated because the emulsifier used in the polymerization process may affect the performance of the product. In addition, the capacity of the emulsion polymerization reactor is lower compared to the bulk polymerization method.
Solution polymerization
Solution polymerization is a method of polymerizing by dissolving monomers in a suitable solvent. In solution polymerization, the operation and polymerization temperature are easy to control, but solvent recovery is required. This method is often used to produce resins such as polypropylene.
To sum up, synthetic resins are prepared in a variety of ways, each with its applicable occasions and advantages. Choosing the right preparation method depends on the type of resin required, product purity requirements, and the specific needs of the production process. Through these methods, we are able to produce a variety of synthetic resins with a wide range of uses, which are widely used in coatings, plastics, adhesives and other fields, promoting the development of modern industry.
