Paper360 - March/April 2012 - (Page 56)

BIOPOLYMERS TECHLINK BIOPOLYMERS in Papermaking RÉGIS HOUZÉ and TIMO PAJARI Functional polymers with very specific properties can improve paper quality and reduce costs S tarch is a natural polymer which has contributed to improving paper quality from the earliest days of papermaking. Wet-end cationic starches, sometimes in combination with surface starches, have been used since the 1960s to improve the physical characteristics of paper and to control costs. Research in wet end starches has recently resulted in a range of functional polymers with very specific properties which improve paper quality and reduce costs, two of which are VECTOR® and STABILYS® developed by Roquette. VECTOR technology is based on a new process which allows the grafting of different functional groups onto the starch polymer chain. These modified products are available in the form of ready-to-use liquids which have FDA approval. Products in this range are differentiated by their dry solids, rheology and charge density. VECTOR was originally developed for alkyl succinic anhydride (ASA) emulsification. Today products from the VECTOR range are used for a number of applications including improving machine runnability and characteristics of grades such as tissue, packaging and decorative papers. Products from the VECTOR range have high and stable charge densities, stable viscosity and concentration during storage and use, a shelf life of up to 12 months, no requirement for a heat exchanger when used for ASA emulsification, and ease of use with a low risk of equipment failure. emulsion protection and stability and is also an important factor for size retention and fixation. The VECTOR biopolymer has a degree of substitution of 0.16 (1.2%N) with a viscosity of 2000 mPa.s-1 at 20% solids. This natural polymer gives excellent emulsion stability, optimizing the ASA efficiency while allowing the selection of the most appropriate grade and addition level of wet-end cationic starch for the paper machine. The high cationicity of VECTOR SC 20157 (DS = 0.16 / SCD = +950 μeq/g) also has a strong reactivity with the fines and this translates into an improvement of overall retention and sizing. Because VECTOR SC 20157 is supplied and used at ambient temperature there is no need for a heat exchanger, unlike a conventional cationic starch which has a temperature of around 80°C after cooking and must be cooled before being used in the ASA emulsifier to limit the amount of hydrolysis that occurs. When cooling, conventional cationic starch solutions are prone to retrogradation which can limit the colloid protection effect and the sizing efficiency. The use of VECTOR SC20157 avoids these problems because the product is stable at ambient temperature. In addition, the fact that the final emulsion is cooler means that the risk of hydrolysis is minimized. These advantages, together with ease of use, give an emulsion of ASA with optimum particle diameter giving improved sizing efficiency. INDUSTRY EXAMPLE: GREY CHIPBOARD SIZED WITH ASA • Before: ASA size with 0.4 % cationic wet-end starch. • After: Total substitution of the wet-end starch by 0.06 % of VECTOR SC 20157 (degree of substitution 0.16) for the ASA emulsification. • Advantages: Improved drainage, steam savings, improved sheet stability at the pickup, COD reduced by 10%, cost saving > €100,000/year INDUSTRY EXAMPLE: CORE BOARD SIZED WITH ASA • Before: ASA emulsified with a synthetic polymer. • After: ASA emulsified with VECTOR SC 2015. ASA: 8-10 l/t, VECTOR: 2.5 – 3.2 kg/t. • Advantages: Cost reduction of €100,000 per year. These results show that it is possible to significantly reduce costs by optimizing chemical additions. In Example 1, the customer was able to save 4 kg/t of wet-end starch which, with a production of 100,000 t/y, is equivalent to 400 tonnes of starch. In addition to the savings achieved with improved sizing efficiency and stability, machine runnability was generally improved and the number of breaks reduced. TISSUE For tissue production, VECTOR is used to improve fiber bonding which reduces refining and allows the use of a higher ASA Polymers for ASA emulsification require concentration and viscosity. The ratio of starch to ASA influences emulsion quality, and the charge density plays a role in determining the 56 Paper360º MARCH/APRIL 2012

Table of Contents for the Digital Edition of Paper360 - March/April 2012

Over the Wire . . . News Summary
Asian Innovation on the Rise
SPECIAL FEATURE: Tissue Industry
North America Shifts to Specialization
A Measured Success
Aligning Rolls in a Paper Machine Winder
Understanding Lightweighting
Sappi Biberist Tests a New Inline Sensor to Control OBAs and Colors
Process Control for Stickies
An Innovative Yankee Coating Program
Biopolymers in Papermaking
Best Practices in Product Development
Employee Work Restrictions Challenge Human Resources
Paper360° Online Exclusives
Association News

Paper360 - March/April 2012