Preparation of an Acrylate Copolymer Latex Containing Acidic Groups

Preparation of an Acrylate Copolymer Latex Containing Acidic Groups 

In this example the use of a Redox initiator to start the polymerisation at a low temperature is illustrated. Previous examples have described isothermal polymerisations, but this reaction pattern is commonly used in industry as it reduces the need for cooling. On a large reactor, the heat required to raise the temperature would be provided by polymerisation. The technique has been termed shotgun polymerisation . The small particle size and an increase in particle hydration due to the acid groups limit the non-volatile content to 35%. Formulation 2-6 is a laboratory scale formulation. 

740g de-ionised water, 12g sodium lauryl sulphate and 150g of a monomer mixture (comprised by 190g methyl acrylate. 190g 2-ethylhexyl acrylate and 20g acrylic acid), are added to a two litre flask and purged with nitrogen. 

After 30 minutes purging, 4g each of ammonium persulphate and sodium bisulphite are added and slow heating applied. 

When the temperqture reaches 30°Q the remainder of the monomer mixture is added over a period of 105 minutes. During the monomer addition, the temperature is gradually increased to 60°C, and then it is raised rapidly to 90°C and held for 30 minutes before cooling. 

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