Product for use in papermaking and preparation thereof

A method for preparation of a paper sizing dispersion, at which

• a reaction product constituting a first sizing agent is formed by reacting maleic anhydride with a fatty acid component, including an alkyl ester of one or more fatty acids selected from a vegetable oil based fatty acid mixture,
• and
• the reaction product thus formed is dispersed by mixing with water,
• and
• the sizing dispersion being prepared by additionally dispersing therein an aluminium compound, which is aluminium sulphate, alum, polyaluminum sulphate or polyaluminum chloride
• (a) mixing the reaction product obtained with water, into which a surfactant, that reduces the particle size of the sizing agent, has been added or is added,
• and
• (b) mixing the sizing dispersion vigorously so as to reduce the particle size of the sizing agent in the sizing dispersion, so that at least 50% of the particles of said dispersion are <2.5 μm, at least 75% are <4 μm and at least 90% are <5 μm.

A paper sizing dispersion, which comprises dispersed in water at least one first sizing agent, and the first sizing agent comprises a reaction product of

• maleic anhydride and
• a fatty acid component,
• wherein
• said fatty acid component comprises an alkyl ester of one or more fatty acids selected from a vegetable oil based fatty acid mixture,
• and
• the sizing dispersion additionally comprises an aluminium compound which is aluminum sulfate, alum, polyaluminum sulfate or polyaluminum chloride characterized by at least 50% of the particles of said first sizing agent in the sizing dispersion, are <2.5 μm, at least 75% of said particles are <4 μm and at least 90% of said particles are <5 μm
• and
• the sizing dispersion further comprises in addition to the first sizing agent, a second sizing agent.