Лако-красочные материалы — производство

Typical plant for the commercial manufacture of acrylic resins for surface coatings applications consists of a large stainless steel reactor, usually with a working capacity of between 5m3 and 20m3, although 30m3 vessels are becoming more common. The reactor is usually designed for a normal working pressure of up to 1-2 bar and working temperatures […]

Some peroxides can be attacked and directly decomposed by the action of solvents. In general for an initiator is increased in the presence of solvents in order of chemical type, as shown below. Alcohols < ethers < aliphatic hydrocarbons < aromatic hydrocarbons < halogenated solvents. Factors of two or three between t^ in the different […]

Polymerisation can only proceed efficiently and economically if sufficient free radicals are present throughout the polymerisation. However, the presence of too many free radicals can have a deleterious effect upon the polymer, resulting in too low a molecular weight, or excessive chain grafting etc. Thus, it is desirable to know how the number of free […]

О О ^ II II ^ Огс_0_0_сО Figure 1-74 Di-benzoyl peroxide (Diacyl peroxides) CH3 CH3 CH3—C — N = N —C— CH3 I I CN CN Figure 1-75 Azo-di-isobutyronitrile (AZO initiators) О О г, 11 11 R-O-C-O—O-C-O-R Figure 1-79Perdicarbonates CH3 R CH3 I I I CH3— c — о — O-C-O — О—C—CH3 I I […]

Free radicals can be produced by catalytic decomposition of a peroxide or, as illustrated below, a reducing agent can produce a Reduction-Oxidation (Redox) couple with the peroxide leading to free radical formation. Generation of free radicals by Redox systems can occur at relatively low temperatures (even below ambient). Thus this type of initiation is of […]

Certain peroxides and azo compounds decompose when heated to give free radicals. This decomposition can occur in a single step: CH3 CH3 CH3 I I heat I. C6H5— С — О — О— С — CeH5 —————— ► 2С6Н5— с — о I I I сн3 сн3 сн3 cumyl radical Figure 1-69 -*• 2C6H6— C-O […]

(i) Free Radical Generation The most commonly used technique for generating free radicals is that of the thermal decomposition of a peroxide or azo compound. Another method frequently used where low temperature polymerisation is required is the generation of free radicals using oxidation-reduction couples (Redox systems). Light sensitive, UV and IR initiators are commonly used […]

Ideally, conversion will keep pace with the feed rate and at t, there will be complete conversion of monomer to polymer. In practice, the conversion will lag a little behind the addition rate, the reaction not being complete until time t2. It is usual, when conducting commercial polymerisations, to monitor the reaction profile against a […]

Monomer and any reaction modifiers are premixed and fed at a predetermined rate into the reaction vessel containing solvent maintained at reaction temperature. Initiation is fed to the reaction vessel at a rate contiguous with the premixed monomer addition. TIME ———— ► Figure 1 -67 Reaction conditions in commercial polymerisations are selected to favour rapid […]

It is essential to remove the large quantities of heat which are liberated during polymerisation. It is therefore imperative that reaction conditions favour a uniform conversion of monomer to polymer in order that the heat of reaction is dissipated in a controlled manner. The majority of commercial polymerisations employ a continuous addition or “drip feed” […]