Module Questions Flashcards
What commodity/general paper grades/markets do you know? Please give at least 3 examples and mention if this is a growing or declining market in the future.
Packaging papers and boards: on the rise, with a 40% market share in 1991 to almost 60% in 2021.
Graphic papers (not including newsprint): declining market, from 36% market share in 1991 to 24% in 2021
Hygiene papers: fairly stable market, increasing as population increases. From 6% market share in 1991 to 9% in 2021
What is the difference between SC and LWC papers? How does the quality of these two grades compare to standard newsprint paper?
Super calendared papers are light weight papers that undergo heavy calendaring to create a smooth pronging surface. They have a basis weight between 39 to 80gsm, a high filler content, and brightness between 68-70%.
Light Weight Coated papers do not usually undergo calendaring, but instead have coating applied to one or both sides to create a smooth glossy finish. The coat weight is usually around 5-12 gsm per side, with basis weights 39-80gsm (the same as SC papers). Brightness is higher at 72-76%.
Newsprint is lighter in basis weight, around 33-55gsm. They usually do not exhibit a glossy surface.
What is a specialty paper and how can it be defined? What are the main differences to general paper grades?
Specialty papers are papers with special characteristics required for specific uses. These uses could be for strength, structure, absorption, functional characteristics, electrical characteristics, cleanliness, or appearance. They usually cannot be used for anything other than their intended purpose, and hence the production of these papers is smaller than common packaging, graphic or printing grades.
Please name as least 5 different specialty paper grades.
Cartonboard, tissue, liquid packaging board, folding box board, LWC, SC.
Please name at least 5 natural fibres which can be used for specialty paper production. What are the main differences compared to normal wood pulp?
Natural fibres include:
* Leaf fibres (abaca)
* Grass fibres (bamboo, bagasse)
* Stalk fibres (wheat/straw)
* Seed fibres (cotton, linters)
* Bast fibres (flax, hemp, kenaf)
What are the main differences between bagasse and bamboo fibres? How to they compare to normal wood pulp?
Bamboo: extremely fast growing, can be pulped via soda or kraft pulping achieving fibre lengths of 1.5-4.5mm. Gives high tensile strength and water resistance, and is used for filter papers and packaging materials.
Bagasse: is the dry fibrous residue that remains after sugarcane extraction.
When refining, bamboo is comparable to softwoods however bagasse produces lots of fines. Bagasse produces very smooth closed sheets due to the short fibres which also increases the opacity. Bamboo has a similar opacity but a much lower density.
What is dissolving (regenerated) pulp? Please give some examples of dissolving pulp fibres and name a few applications of these fibres.
Dissolving pulp can come from either wood or cotton linters. There are many different manufacturing processes which can generate a variety of different products such as nitrates (for explosives), acetates (for films) and viscose (for textiles).
You typically need a high cellulose content with a defined viscosity, and high purity.
What paper properties can be improved with specialty fibres (natural, synthetic or regenerated fibres) compared to standard wood pulp fibres?
Absorbency- viscose fibres are highly hydrophilic.
Abaca is very good for improving tensile strength and folding resistance.
Kenaf for improving wet strength.
Polyester can improve bulk and tear strength.
What is the difference between thermal and piezo print heads? Name advantages and disadvantages.
Thermal print heads use heat to produce air bubbles, whereas piezo uses charged crystals which expand.
Thermal:
+ cheaper technology
- limited usable inks
- limited ink properties
Piezo:
+ wide range of usable inks
+ can modulate the drop size giving better resolution
+ higher drop rates
+ longevity
- limited number of nozzles per row
- higher cost per nozzle
Describe the difference between swellable and microporous ink jet coatings. Which materials are used in the coating and what are the advantages and disadvantages of each type.
With swellable coatings, the coating forms a film and the ink stays on top of this coating. The coating itself is made from water soluble polymer. With microporous, the ink penetrates into the coating through capillary forces. The coating is made with pigments (i.e. clay) or binders (I.e. latex).
Swellable:
+ excellent strike through
+ good dusting
Microporous:
+ very quick drying
+ excellent link sharpness
+ good curl
Which important properties of an ink jet paper do you know? Name at least 5 properties.
- Colour
- Gloss
- Bleed
- Resolution
- Optical density
- Curl
What are the different phases when printing on an ink jet paper?
- Printing
- Wetting
- Absorption
- Fixation
- Drying
How does a typical Matt inkjet coating look like? Name the different components, their functions and an example.
A typical matte inkjet coating consists of two components, the raw base and the ink receiver layer.
What is a décor paper and what are the requirements of this paper? Name at least 3 applications where décor papers are used.
Décor paper is the carrier of the colour and resin for the manufacturing of decorative laminate surfaces.
The requirements:
* Complete cover of the inhomogeneous substrate
* Resistance to different environmental influences I.e. light, chemicals
* Good mechanical performance I.e. scratch resistance
* Printability and treatability
* Unlimited design variety
Applications:
* Bathroom surfaces
* Flooring
* Doors
* Furniture surfaces
* Window sills
What is the main filler used for décor papers? Please explain why only this type of filler can be used and why other fillers don’t work.
The main filler used is Titanium Dioxide as it is a strong opacifier. It can be produced in large quantities, is non toxic and easy to handle. Many other fillers are not functional:
Kaolin- becomes transparent in melamine
Lead carbonate- toxic
Diamond- expensive
Please explain which factors can influence the impregnating characteristics of a décor paper.
Refining, wet pressing and calendaring can effect the number and shape of pores and sometimes displacement of air from pores. In turn, this leads to poor resin pick up, distribution, and penetration.
Please name 5 paper properties of a décor which can influence the printing result during rotogravure printing.
- Surface quality
- Paper structure
- Smoothness
- Absorbency
- Thickness
- Gloss
What is the difference between LPL and HPL laminate. Describe the different pressing conditions and the different features and application of the final laminates.
LPL and HPL are both types of melamin films. They stand for Low and High Pressure Laminate.
LPL:
* Temp 140-200 degrees Celsius
* Pressure 20-40 bar
* For less demanding applications
* For vertical surfaces
* Pressed directly onto particle board, single layer build up.
HPL:
* Temp 130-150 degrees Celsius
* Pressure 70-100 bar
* For high end furniture
* High wear resistant and stain resistant surfaces or horizontal surfaces e.g. kitchen countertops
* Laminate is glued onto substrate, multi layer build up.
Name 4 different types of labelling methods and 3 different types of label paper materials.
Labelling methods:
* Wet glue labelling
* Self adhesive labelling
* Sleeve labelling
* In mold labelling
Label paper material:
* Uncoated natural label papers
* Simple one-time coated label papers
* High gloss cast coated papers
Name 5 important paper properties to obtain a good labelling result. How can the properties be influenced in the paper making process?
For good labelling results:
* Good dye cutting properties which are influenced by waxes
* Flatness of the label paper which is influenced by the drying section
* Stiffness of the paper which is influenced by the fibre intake or long fibre
* Wet strength properties which is influenced by wet strength agents
* Quick adhesion, which is influenced by rough reverse side
What are the three main types of adhesive used in the production of a self-adhesive label paper?
- Emulsion adhesives: Account for around 75% of the production, majority of water-based acrylics, typical coating weights are approximately 20 GSM.
- Hot melt adhesives: Account for around 16% of market share it is a thermoplastic adhesive supplied and dry form which melts at temperatures ranging from 65°C To 180°C examples are synthetic rubbers
- Solvent adhesives: Account for around 9%. High manufacturing costs, critical regarding environment issues, used in High-performance applications, for example, clear and clear, pasteurisation
