In the field of Unsaturated Polyester Resins (UPR) we supply our clients with know-how, technology and equipment / machines for process lines as well as turnkey plant, including engineering, procurement, construction, training, commissioning and initial assistance in marketing.
UPR are most commonly used as composite materials which basically bridge the gap between conventional plastics, commodity plastics and specialist engineering plastics. Such plastics are widely used in applications where advantage may be taken of their good range of mechanical properties, corrosion resistance and low weight.
MAIN ADVANTAGES OF TECHNOBELL’S UNSATURATED POLYESTER RESINS PRODUCTION PROCESS
- STABILE QUALITY
Highly accurate control of both the time / temperature diagram of the reactor and of the difference in temperature between the reactor and the heating fluid obtains the best possible results from the resin and avoids the formation of by-products.
- LOW RAW MATERIAL COSTS
Based on raw material price changes, Technobell can vary the raw material composition for each type of UPRs to reach highest product performance parallel with lowest available raw material cost.
- LOW ALCOHOLS (GLYCOLS) EXCESS
The specially designed column enables us to operate with low glycol excess. This excess is in range of 2-3 wt% in the reaction water (depending on resin recipe) while older processes involves glycols excess of 5-6%. The benefit of reducing the amount of glycols in circulation is the reduction of resin production costs, and waste water pollution. Overall UPR production yield reaches 99,9 wt% (excluding reaction water formation).
UPR composites are made up of at least two separate components: reinforced fibre (glass, kevlar, carbon, etc.) and embedding matrix (UP Resin). Production takes place by introducing reinforcement while the resin is in an uncured, liquid state.
PROCESS DIAGRAM OF TECHNOBELL’S UNSATURATED POLYESTER RESINS TECHNOLOGY
UNSATURATED POLYESTER RESINS PRODUCTION PROCESS DESCRIPTION
Unsaturated polyester is formed by chemical reaction between glycol with di-basic unsaturated acid. This reaction, together with the addition of compounds such as saturated di-basic acids and cross-linking monomers, forms the basic process of unsaturated polyester manufacture. As a result there is a whole range of polyesters made from different acids, glycols and monomers – with combination of different ratios between them, all having varying properties.
Process of cross-linking
The molecular chains of uncured polyester can be represented as follows, where »B« indicates the reactive sites in the molecule.
With addition of styrene »S« and in the presence of a catalyst, the styrene cross-links the polymer chains at each of the reactive sites to form highly complex three-dimensional network cured polyester as presented.
Cured polyester is now chemically resistant (and usually) hard solid. The cross-linking or curing process is called »polymerization«. It is a non-reversible chemical reaction.
Filling and mono-ester formation
On basis of predetermined type of formulations raw materials are fed into the esterification reactor. Liquid raw materials (glycols, Phthalic and Maleic anhydride) are fed from the storage tanks. Solid raw materials (fumaric acid, iso-phthalic acid and terephthalic acid) are dozed in solid form through solid feed system directly into the reactor.
After the glycols are charged, the stirring and heating is switched on. Then the acids and anhydrides are fed to the reactor. Depending on the recipe more stages could be necessary. Following, the mass is heated up to the initial temperature of the exothermic reaction and maintained until the complete formation of mono-ester.
Esterification
The temperature and vacuum inside of the reactor are maintained until the UP resin reaches characteristics prescribed by the recipe. During the esterification the water is removed from the reactor through the column which separates the glycols from water. Glycols return to the reactor, while the water is removed from it. The reaction and distillation is carried out until the increase in weight of reaction water is practically zero. This also means that reaction in the reactor has reached equilibrium and esterification is complete. At the end of the reaction vacuum is applied to the reactor. The polyester resin formation is controlled by measurement of acid value and viscosity. Reaching the end of reaction the reactor is cooled down.
Dilution phase
The resin is transferred to dilutor which is equipped with high efficiency cooling and with a condenser for styrene vapours, which are after condensation returned in dilutor. The cooling of the product in the dilutor continues also after the complete transfer of resin from reactor until the product reaches the required temperature. In the dilutor the resin is further adjusted to viscosity, reactivity and shelf life desired by the client with addition of inhibitors or promotors. The final product is then transferred to the resin storage tanks.
PROCESS VALUES
Process values
| PROPERTIES: | Guaranteed | Expected |
| Yield (wt%): | min 99,5 % | 99,7 – 99,8 % |
*Yield → ton of product UPR / tons of sum raw materials in percentage (excluding reaction water formation)
