Innventias most recent focus in the field of process chemistry has been retention chemistry, fibre surface analysis and alleviation of wet-end problems caused by dissolved and colloidal substances.

One particular aspect has been to improve the formation of paper at a given retention level. Such studies include pilot papermaking trials with various types of formation aids and their integration with retention aid systems (e.g to be able to produce high filler papers) as well as studies on how fibre flocculation is affected by chemical additives.

In conjunction with topochemical surface charge grafting, detailed studies have been conducted on surface charge distribution in the cell wall of fibres and how it affects polyelectrolyte adsorption and performance of various wet-end additives. One particular aspect has been to replace beating with additives, while maintaining the productivity of paper machines.

Wet-end chemistry

Regarding wet-end chemistry our focus is to solve problems related to detrimental substances in the paper mill. When increasing the closure of the papermaking process, the organic substances in the process tend to accumulate and may cause problems, e.g. by deposit formation or by disturbing the effect of performance chemicals. A survey of the process can be useful in order to get knowledge of the chemical status of the process and from this solve the problems.

Another field of interest is the efficiency of additives, such as fixatives and retention aids. We have carried out a number of projects dealing with development and optimisation of new additives, efficiency tests, sensibility for detrimental substances etc.

Analysis of the wet end

• Dewatering time and permeability in fibre suspensions using a DDA (Dynamic Drainage Analyser).
• Zeta potential analysis of fibres (Mütek SZP).

Analysis of white water

• Cationic demand (Mütek PCD).
• COD (Dr Lange cuvette method).
• Carbohydrates, total content (orcinol).
• Carbohydrates, monosaccharide composition (CZE).
• Turbidity.
• TOC.
• Extractives.
• Lignin.
• Particle size distribution.

These methods can be applied on white water and on different fractions of white water. The following procedures can be used:

• Fractionation of white water into colloidal material and dissolved material;
• Ultrafiltration of dissolved material into high and low molecular mass material.