How is polyester resin produced?

Release time:09-03-2020

Polyester bai resin is the abbreviation for unsaturated […]

Polyester bai resin is the abbreviation for unsaturated polydu ester adhesive. The unsaturated polyester adhesive is mainly composed of unsaturated polyester resin, initiator, accelerator, filler, thixotropic agent, etc. The adhesive has low viscosity, easy wetting, and good manufacturability. The cured adhesive layer has high hardness, good transparency, high brightness, fast curing at room temperature, good heat resistance, and excellent electrical properties. The disadvantages are large shrinkage, low adhesive strength, poor chemical resistance and water resistance, and are used in non-structural adhesives. Mainly used for gluing glass fiber reinforced plastic, hard plastic, concrete, electrical potting, etc.

The difference between  polyester resin and alkyd resin is that the raw material of synthetic polyester resin does not contain vegetable oil or fatty acid derived from oil. Polyester can be divided into saturated polyester and unsaturated polyester. Saturated polyester means that the synthetic raw materials do not contain unsaturated bonds except benzene ring.Introduction to  saturated polyester (oil-free alkyd) resin.amorphous polyester resins
   Different types of saturated polyester resins with different characteristics can be synthesized by using different polybasic acids and polyols. If the diols and dibasic acids with linear structure are used, the result is a polyester resin with only linear structure. If the polybasic acid used contains benzene ring (for example: phthalic anhydride, terephthalic acid, trimellitic anhydride, etc.) What is produced is a polyester resin containing a benzene ring structure. If a chemical reaction is used to introduce other components except polyols and polyacids, the produced is a modified polyester resin.
If the synthetic polyester resin adopts linear structure of polyol and polyacid, the synthesized resin has a linear structure and is very flexible. The main use is not in the coating industry; the nylon encountered in daily life and work is very typical Linear polyester, the most typical linear polyester nylon-66 is the product of hexamethylene diamine and 1,6-adipic acid. From the structural point of view, it can also be synthesized with 1,6-hexanediol and 1,6-adipic acid.
"Synthetic polyester resins, if a polybasic acid with a benzene ring reacts with a polyol to synthesize a resin containing a benzene ring structure, the rigidity of the benzene ring gives the resin hardness, and the stable structure of the benzene ring gives the resin chemical resistance. The raw materials for the synthesis of saturated polyester resins are mainly dihydric alcohols, dibasic acids and trihydric alcohols, and some monohydric alcohols or monohydric acids. The most commonly used alcohol is neopentyl glycol, and its esters have much better water resistance than ethylene glycol and propylene glycol. The triols are mainly trimethylolpropane and trimethylolethane. The most commonly used aromatic dibasic acid is isophthalic acid. Because isophthalic acid has better salt spray resistance, chemical resistance and water resistance than phthalic acid, the application of isophthalic acid in polyester resins More common. Aliphatic dibasic acids are also used in synthetic polyester resins, such as adipic acid, azelaic acid and sebacic acid, and adipic acid is more commonly used. Most resins contain aromatic dibasic acid and aliphatic dibasic acid. The molar ratio of aromatic dibasic acid to aliphatic dibasic acid is the main factor to control the resin Tg.
When synthesizing polyester resin, if some other ingredients are introduced through chemical reaction, it can have properties that polyester resin does not originally have, and achieve the purpose of improving and highlighting certain properties, so as to achieve special application performance requirements. Currently, the ring is mostly used. Oxygen, acrylic, silicone modified polyester resin.
  The polyester resins used in coatings are generally low molecular weight, amorphous, branched, and crosslinkable polymers. It is generally made of polyhydric alcohols and polybasic acid esters, and has two structures, pure linear and branched. The paint film prepared by pure linear structural resin has better flexibility and processing performance; branched structural resin prepared The hardness and weather resistance of the paint film are outstanding. By adjusting the polyester resin formulation, such as excessive polyol, hydroxyl terminated polyester can be obtained. If the acid is excessive, the result is a carboxy-terminated polyester. The most commonly used saturated polyester resin in the coating industry is a polyester resin containing terminal hydroxyl functional groups, which is cured into a film by cross-linking with resins such as isocyanate and amino resin. Different raw materials make different contributions to the performance of the resin. When selecting raw materials, it is necessary to consider the performance requirements of the resin. Choose the corresponding raw materials that can help the required performance of the resin, from providing functionality, hardness, flexibility, etc. consider.