Novel solutions to new problems in paper deinking

Purpose – This paper aims to describe and evaluate the traditional methods for effective ink removal during the recycling of printed papers. Additionally, novel techniques for dealing with the newer “difficult to deink” inks such as toners from photocopiers, UV-cured ink films and liquid toner suspensions or Electroinks® are to be evaluated.

Design/methodology/approach – High intensity ultrasound was applied to pulps derived from papers printed with these newer inks in order to evaluate its effectiveness in detaching the inks from paper and establishing the resultant ink particle size distributions.

Findings – When exposed to ultrasound at a frequency of 20?kHz, it was found that “difficult to deink” pulps did exhibit significant ink detachment. In the case of toners, temperature did have an effect on particle breakdown with larger numbers of particles produced at temperatures well below the softening point which was attributed to a greater brittleness of the toner at lower temperatures. Electroinks® can be effectively de-inked by exposure to ultrasound coupled with washing under neutral conditions. With all the inks investigated, exposure to ultrasound resulted in the detached ink having particle size distributions that can be removed by conventional flotation and washing techniques.

Research limitations/implications – The exposure of the pulp to ultrasound was only carried out using a batch-wise process. A future development would be to use a continuous flow system incorporating an annular ultrasound horn.

Practical implications – Introducing ultrasound exposure into a conventional deinking plant, all post-consumer printed waste paper could be deinked without the use of deinking chemicals.

Originality/value – The findings are of interest to those in paper recycling.

MATAR was founded in 2005 to build on a well-established base of scientific research at UAL. During its time, MATAR has undertaken research at the intersection of the sciences and the arts in order to apply science and technology in the fields of communication, conservation, fashion, art and design.

A considerable amount of research into the behaviour of prints and printing materials has been carried out at Camberwell College of Arts and the London College of Communication. This has resulted in a numerous research publications as well as the successful completion of doctoral research projects by eight PhD students. Their theses have been concerned with a wide range of topics related to the intersection of science with art, design and communication, including print recognition, stability of printed materials, ultrasonic deinking, conservation of 19th century watercolours and ink transfer mechanisms in flexographic printing.

Prior to the establishment of MATAR, the University had established a high international standing and a solid body of research output in the core areas of materials science especially as they applied to conservation and printing.
From its foundation in 2005, MATAR was led by Dr Andrew Manning, who had an outstanding record of research and successful PhD supervision and completions. The Centre attracted researchers in other specialist subject fields and thus provided a framework for emerging as well as existing research strengths in science and technology subjects. The Research Centre was a centre of excellence for ink/substrate projects, as well as having a wider portfolio which included conservation science, colour imaging and document security.

In MATAR subjects, published papers are the primary vehicle for disseminating research outcomes. Research is also disseminated through symposia, conferences and seminars, and MATAR has made such events a priority. MATAR research has had a direct impact on undergraduate and postgraduate teaching, a number of MATAR members being also course directors and able to readily integrate research results with the curricula. Students are encouraged to produce publishable research as part of their course.

MATAR was not redesignated beyond 2010, but closed in July of that year. Despite the unit’s closure, in the specialist laboratories across the University, the Centre had an outstanding range of powerful and up-to-date measurement and test equipment which is still available for use.