Лако-красочные материалы — производство

The initiators used in emulsion polymerisation are exclusively of the free radical type and, of necessity, they must be water soluble. The free radicals may be generated thermally or by use of an oxidation-reduction (or redox) couple. Hydroperoxides are often used (e. g. t-butyl hydroperoxide) particularly as a post reaction initiator to scavenge the last […]

The surfactants (and colloids) control many of the properties of emulsion polymers and some knowledge of their nature and characteristics is a necessary pre-requisite for successful formulation of latex systems. Any molecule containing a hydrophilic group chemically bound to a hydrophobic group can act as a surfactant. When a surfactant is dissolved in a water/oil […]

Most acrylic monomers will undergo emulsion polymerisation, although the monomer molecules must be available in a solubilised state, either in the form of surfactant stabilised droplets or in micelles. Where the acrylic monomer contains a long chain alkyl group (e. g. lauryl and stearyl acrylates and methacrylates) polymerisation may be retarded by steric factors resulting […]

The quality of the water used in emulsion polymerisation is important. The presence of polyvalent metal ions can cause instability. De-ionised water is preferred for the process, and usually a limit of 250,000 ohm resistance is placed on the water used. Commercial processes are conducted with a water composition of between 35 and 65% of […]

The basic components of an acrylic latex polymer system are: i) Water ii) Acrylic monomers iii) Surfactants iv) Initiator combinations v) Modifiers vi) Buffers In addition to the above components such as plasticisers and coalescing solvents are added when the coating is prepared, to improve film forming and film performance characteristics.

The precise mechanism of emulsion polymerisation remains a matter for debate. Whilst theoretical studies have given rise to the classical theories of Harkins and Smith-Ewart, commercial polymerisations do not always behave as those theories predict. There are a number of reasons for this. For example the water solubility of various monomers has a profound effect […]

Resin-water emulsions can be produced by the post-reaction emulsification of a condensation or addition polymer, by the use of surfactants or emulsifiers to form an “oil-in-water” emulsion of the polymer in the aqueous phase. This is simply a method of obtaining a polymer in an aqueous medium. This type of emulsion is different from a […]

In the following examples, illustrating the preparation of thermosetting acrylic resins, addition polymerisation of the monomers to form a copolymer is followed by methylolation of the amide group on the acrylamide with paraformaldehyde. By conducting the methylolation in the presence of an alcohol, such as butanol, the methylol groups can be etherified and hence are […]

TABLE 1-18: FORMULATION FOR AN ACRYLIC COPOLYMER IN MEK Benzoyl peroxide 00.12 Methyl methacrylate 23.50 Ethyl acrylate 35.25 Methyl ethyl ketone 41.13 Total 100.00 Procedure 1. Benzoyl peroxide is dissolved in a mixture of methyl methacrylate and ethyl acrylate. 2. 40% of the monomer mixture and methyl ethyl ketone are charged to a reactor set […]

Oxygen acts as an inhibitor and a nitrogen sparge or purge can be used to exclude air and thereby oxygen from the air. Unlike the monomer purification process employed when undertaking polymerisations for academic purposes, for commercial operations it is not usual to remove inhibitor from the monomer before polymerisation this being regarded as a […]