Characterization methods for fibres and paper

Ziel

A. BACKGROUND

Competition from other media and materials and increasing demands from customers force the pulp and paper industry to increase its know-how and so improve its competitive edge. To meet these challenges the quality of paper as both an information carrier and as a packaging medium must be further developed.

A.1. Paper - an important information carrier

Paper has long been the most important material for the dissemination of information. It is cheap and environmentally friendly in compliance with sustainable development. For the reproduction of letters and pictures, the paper surface is the critical part. As paper is composed of fibres, fines and mineral fillers, the surfaces as well as the structural characteristics of these components will critically determine the properties of the paper surface. The demand by the printer for paper surface uniformity, smoothness and receptivity to the printing inks is ever increasing. New printing methods are developed, putting new requirements to paper surfaces.

The papermaker has to meet the challenges of the new information media in order to maintain his market position. His strategy must be to improve the quality and cost relationship for paper, relative to the alternative media for picture reproduction, primarily the electronic ones. Multicolour printing is therefore expanding rapidly.

A.2. Paper - an important packaging material

Paper is also an important packaging material, but paper is in strong competition with synthetic materials.

The ability of paper to lend stiffness and strength to a container or sack depends to a high degree on the structural composition of the paper sheet. Stratified sheets and multi-layer sheets are examples of advanced structures.

The surface character is also very important to the quality of packaging grades. The physical and chemical characteristics of the surface determine its ability to absorb liquids, which is a critical property for many packaging grades. Packaging paper is also increasingly required to carry a printed image for advertising and information together with its use as a packaging medium.

A.3. Papermaking fibres - a combined result of raw materials, defibration and fibre development

The papermaking fibres have a most intricate structure. The dimensions of the papermaking fibres differ strongly; primarily between various wood species, but also within one species, and indeed within the trunk of each tree. Growing attention has been given to the systematic use of the variation of fibre size and coarseness characteristics to produce better paper products.

Dependent on the defibration method, the ruptures in the wood matrix may occur through the interfibre structure or the fibre wall material. In the chemical pulping processes, the intrafibre cement (lignin) is mainly dissolved, leaving the fibres intact, whereas the fibre separation in the mechanical pulping processes occurs mainly through the interfibre material, however to a large extent also through the fibre wall. Besides intact fibres, there always will be a large fraction of broken fibres and debris in the paper, especially for paper containing mechanically produced pulp.

The compressibility of the tubular fibres has very important consequences for the bonding capacity in the paper sheet and for paper surface smoothness. Chemical pulp fibres are very flexible compared to mechanical wood fibres, where the remaining lignin renders them stiff and fairly uncollapsable. New pulping and pulp treatment methods are emerging. The consequence of this on fibre characteristics and paper properties is still not fully elucidated.

A.4. Paper - reflecting the characteristics of papermaking fibres, other papermaking components and papermaking processing

For both coated and uncoated paper grades the bulk and surface structure reflects the properties of the building bricks of the sheet including fibres, fillers, coating pigments and papermaking additives. In order to characterize the paper surface and the bulk properties of paper, one has to have a thorough understanding of the papermaking components, especially the fibres; their structural, mechanical, topochemical and chemical composition generally; especially with regards to the surfaces. In the formed paper, the surface consists of basically randomly oriented wood cells. Its topographical and chemical characteristics reflect the characteristics of the constituting fibres.

For printing paper the role of the surface is obvious. For completeness, it should be emphasized that even within the two other main end use areas for paper, i.e. packaging and absorption, the surface will be very critical. For most packaging paper and board materials, the surface layer is very critical; and absorption is a surface reaction.

Also, the effects of the defibration processes as well as the paper forming and converting processes on paper properties have to be thoroughly known in order to maximize paper quality. Today, techniques for the production of paper as an engineered product are being developed, for instance by using multilayer forming units.

A basic requirement for the improvement of printing paper, is a deeper understanding of the structural components of paper, their interaction and the structural characteristics of paper as a whole, primarily the surface. The main component of paper is the cellulosic fibre.

A.5. A European perspective

Europe enjoys currently a fairly good volume balance in paper production and consumption. It can be safely stated that the quality demands in the West European market, for most grades, is superior or equivalent to the products offered in any other markets.

The threat to paper comes from electronic media and other materials. This has already been commented on. There are however also other challenges. The high growth rate in wood plantations in tropical countries producing hardwood of high fibre quality, combined with large paper production units, and low production costs, pose a significant threat to the European paper producer.

To maintain the European position, paper quality has to be continuously improved. For this a strong knowledge base is a must including means to characterize the material used throughout the production chain.

A.6. The proposed COST Action

In the paper science communities around Europe, significant efforts are currently made to develop methods to characterize papermaking fibres, paper structure and paper surfaces. In other science fields, like surface chemistry and material science, new very promising techniques have been taken into use, and it is felt that the pulp and paper industry should expand its use of such techniques.

It is felt that this community of papermakers and scientists in other fields will all be stimulated by and benefit from a cooperation in a COST Action.

The planned activities are pre-competitive, allowing the cooperation to the common good. The emphasis will be on methods of characterization, in order for the European paper industry to combine its efforts to get means for improved analysis of their fibre materials, to better modify pulping and fibre treatment processes, and develop new and better functional properties of paper.

B. OBJECTIVES AND BENEFITS

The main objective of the Action is to develop new methods to characterize the dimensional, structural, mechanical and chemical properties of papermaking fibres and paper, in order to facilitate improved processes and products in the paper industry, primarily the graphic and packaging paper sectors.

The proposed Action will establish a forum where information on the characteristics of fibres and paper generally is stimulated and shared, in order to assist the European paper industry in its efforts to further improve the utilization of its raw materials, and to improve the quality of its paper.

Some of the benefits of the suggested COST Action are felt to be:

- wider dissemination of the basic knowledge of fibres and paper,

- improved cooperation between European paper science communities,

- increased exchange of ideas between paper communities and scientists in other fields,

- raised cooperation between scientists, paper producers and paper industry suppliers,

- stimulation of cooperation across country borders,

- initiation of joint European research programmes on the characterization of fibre and paper.

C. SCIENTIFIC PROGRAMME

C.1. Types of activities

The suggested Action will be in compliance with the general rules of COST and can include:

- arranging workshops, conferences, seminars etc.,

- exchange of experts, scientists, and graduate students for training,

- exchange of reports, publications, experimental procedures,

- state of the art conferences and workshops,

- joint projects in specific areas may be launched by two or more of the participants in the Action.

C.2. Scientific areas

The scientific areas in consideration will be those focusing on methods for characterizing fibres, paper structure and surface properties. Examples:

- characterization of paper making fibre; structurally, mechanically, chemically etc.,

- characterization of the fibre surface; structurally, topochemically, dry and wet,

- characterization of paper 3D structure,

- paper surface characterization; structurally, mechanically, optically, chemically etc.,

- characterization of chemical and mechanical surface treatments, like surface sizing, pigment coating and various calendering,

- characterization of paper surface structure uniformity,

- methods to characterize the effects of converting and climatic changes on paper characteristics.

C.3. Actual experimental techniques

The proposed COST Action has two interrelated main areas, i.e. methods for

Characterization of papermaking fibres, and
Characterization of paper (surface and 3D structure).

In the following, some comments on potential experimental approaches and methods to be used in the Action are listed.

C.3.a Fibre characterization

- new methods for characterization of fibre populations by image analysis; with respect to dimensions, shape and surface properties, as well as cross-sectional details. Strong tools in this area will be Scanning Electron Microscope (SEM, ESEM) and Confocal Scanning Laser Microscope (CSLM),

- other methods for assessing important fibre properties, like flexibility, kink, curls, degree of swelling; bonding ability,

- various methods, optical and chemical, for the characterization of fibre surfaces, after defibration as well as after the addition of additives. Here, the effects on fibre surfaces by substances accumulating in the system as a consequence of system closure and the reduction of fresh water consumption will be important. Effect on fibre bonding strength potential. Among available methods to be considered for investigation of the surface structure as well as the chemistry of the fibre surface are nearfield microscopy, like Atomic Force Microscopy (AFM), Atomic Tunneling Microscopy and Optical Tunneling Microscopy, and Scanning Electron Microscope (SEM),

- other chemical tools appropriate to investigate these issues as ESCA, SIMS (Secondary Ion Mass Spectroscopy) and FT-IR microscopy etc.

C.3.b Paper characterization

Most of the methods suggested for the study of fibres, are as well suited for the study of paper. Some additional comments:

- image analyses techniques for the evaluation of surfaces, as well as details have developed rapidly in recent years. The methods in this field are expanding rapidly,

- characterization of 3D structure of paper methods for characterization of the distribution of furnish components,

- methods for characterization of the sheet structure and dimensional stability of paper,

- investigating topographic details by high resolution methods like AFM,

- measuring the distribution of pore volume in the paper surface by CSLM,

- investigating the capillar structure of paper surface, using CLSM,

- optical methods for the assessment of local gloss variation, and their causes,

- printing ink transfer, analysed by optical microscope and SEM, as well as CLSM.

D. ORGANIZATION AND TIMETABLE

The Action will be led by a Management committee (MC). Responsibility for the detailed planning, execution and documentation of each individual activity is delegated by the MC to 3 different working groups, each led by a professional appointed by the MC.

The COST activity will be carried out in cooperation with existing research programmes within the area, such as those carried out by the main pulp and paper research laboratories in Europe, the main suppliers of pulp and papermaking equipment, as well as suppliers to the paper industry of chemical additives. Also, scientists from other fields are encouraged to take part in the Action in order to provide an input of outside ideas. The ongoing Action E1 Paper recyclability is related to the suggested one, exchange of information and ideas will take place as long as E1 is still in operation (1998). The Action is also related to another proposed new cross-sectorial Action with the title: Wood properties for industrial use.

Action structure

The duration of the Action is suggested to be four years. Meetings are planned to be held twice a year in the working groups, and once a year in the MC.

The contacts between researchers as a result of the Action, is supposed to lead to exchange of researchers between laboratories, and from one field to another, as between paper science and material science.

E. ECONOMIC DIMENSION

The following COST countries have actively participated in the preparation of the Action or otherwise indicated their interest: Finland, France, Hungary, Netherlands, Norway, Portugal, Slovenia, Spain, Sweden and the United Kingdom.

Participation of at least 3 more countries is foreseen, bringing the total to between ten and fifteen.

On the basis of national estimates provided by the representatives of the countries mentioned, and taking into account the coordination costs to be covered over the COST budget of the European Commission, the overall costs of the activities to be carried out under the Action have been estimated, in 1996 prices, at roughly ECU 9 million.

This estimate is valid under the assumption that all the countries mentioned above, and 2-3 others, will participate in the Action. Any departure from this will change the total costs accordingly.

Programm/Programme

IC-COST - European cooperation in the field of scientific and technical research (COST), 1971-

Thema/Themen

14 - Forestry

Aufforderung zur Vorschlagseinreichung

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Finanzierungsplan

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Koordinator

N/A

EU-Beitrag

Keine Daten

Adresse

Finnland

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