Лако-красочные материалы — производство

1. Free-Radical Formation The decomposition of initiators is induced by heat in the case of molding compounds or by accelerators at temperatures below the decomposition temperature of the initiator in the case of cast polyester resins. Two types of accelerators are used, metal salts—mainly cobalt salts—and amines. The oxidoreduction of metal salts by peroxides produces […]

The maximum exothermic temperature reached, the time required for the reaction to attain peak exothermic temperature, and the time of gelation are important factors to be considered when selecting a resin. Reactivity tests provide a method for determining the behavior, uniformity, and curing characteristics of a resin. The use of a resin for a specific […]

Selection of the proper catalyst and the amount to be used for any application depends on the resin, the temperature at which the resin is to be cured, the required working or pot life, and the time of gelation. No catalyst is available that can meet all the requirements. Therefore, combinations of catalysts, or of […]

The chemical structure of unsaturated polyester is more complex than expected in view of the chemistry described above. The 13C nuclear magnetic resonance spectra of unsaturated polyesters present many small peaks that cannot be assigned to carboxylic or hydroxylic end groups alone. These are due to a number of side reactions. Of these, the addition […]

The theoretical analysis of the kinetic data for bulk polyesterification reactions is difficult because of the high concentrations of reactive end groups at the beginning of the reaction and because of the changes in dielectric constant of the medium during the reaction [3]. According to Flory [4], only the experimental results obtained for extents of […]

A. Reaction Between Dicarboxylic Acids or Anhydrides and Diols The synthesis of unsaturated polyesters usually involves a bulk reaction at elevated temperatures between dibasic acids or anhydrides and diols. A general reaction scheme for maleic anhydride and 1,2-ethanediol can be illustrated as follows: During this reaction most of the maleate groups are isomerized into fumarate […]

A. Pizzi Ecole Nationale Superieure des Technologies et Industries du Bois, Universite de Nancy I, Epinal, France I. INTRODUCTION Although unsaturated polyester resins are often regarded as casting plastics in at least one important use, glass-fiber lamination, they are used as adhesives. The method of binding glass-fiber mats with unsaturated polyesters started in 1942 by […]

Vinyl acetate homopolymers are simply-made adhesive bases manufactured by addition polymerization in the presence of water and stabilizers. They are made commercially by the batch reactor process or by the Loop reactor continuous process. External plasticizers such as dibutyl phthalate are often added to confer flexibility and to lower the temperature at which they form […]

Parts (%) PVA homopolymer (58% solids, 10% DBP) 82.6 Dibutyl phthalate (DBP) 5.7 Ethyl acetate 5.5 Calcium carbonate filler (micronized) 4.8 Preservative 0.2 Water 1.2 100.0 Process: Blend all ingredients except the filler with the PVA. When complete add the filler slowly, blending well between additions. II. APPLICATIONS Applications for poly(vinyl acetate) homopolymers include: Wood […]

A Loop continuous reactor formulation is given below, where the redox initiator is of an unusual manganese type. Parts by weight (kg) 1. Initial reactor filling Water 50 2. Water/stabilizer solution feed (feed rate: 3.95 kg/min) Water 236.66 Poly(vinyl alcohol) (80% hydrolysed) 11.36 Sodium bisulfite 3.79 3. Monomer feed (feed rate: 8.52kg/min) Vinyl acetate 440.18 […]