Holmen Iggesund grades

Solid Bleached Board (SBB, GZ) multiply construction

SBB is made exclusively from bleached chemical pulp.

It usually has a pigment coated top surface and can also be pigment coated on the back.

Illustration of solid bleached board layers

Folding Box Board (FBB, GC1), white back, multiply construction

FBB, white back, is made from layers of mechanical pulp sandwiched between layers of bleached chemical pulp.

The top layer is pigment coated. The back is thicker than FBB, cream back, and can also be pigment coated.

Illustration of Folding box board GC1 layers

Folding Box Board (FBB, GC2), cream back, multiply construction

FBB, cream back, is made from layers of mechanical pulp sandwiched between layers of bleached chemical pulp.

Illustration of Folding box board GC2 layers

 

Abbreviations/keys

  According to DIN 19303
GZ Coated SBB
AZ Cast Coated SBB
GC1 Coated FBB, white back
GC2 Coated FBB, cream back
GN Coated SUB, white or brown back
GT Coated WLC, cream or white back
GD1 Coated WLC, grey back (spec.volume <1.45 cm³/g)
GD2 Coated WLC, grey back (spec.volume 1.3 to 1.45 cm³/g)
GD3 Coated WLC, grey back (spec.volume <1.3 cm³/g)
UZ Uncoated SBB
UC1 Uncoated FBB, white back
UC2 Uncoated FBB, cream back
UT Uncoated WLC, cream or white back
UD Uncoated WLC, grey back
SBB Solid Bleached Board
FBB Folding Box Board
SUB Solid Unbleached Board
WLC White Lined Chipboard
G Gestrichen, coated
U Ungestrichen, uncoated
A Gussgestrichen, cast coated
Z Chemisch gebleichte Frischfasern, bleached virgin chemical pulp
C Holzstoff, virgin mechnical pulp
N Chemisch ungebleichte Frischfasern, unbleached virgin chemical pulp
T Rezyklierter mit weisser oder gelber Rückseite, recycled with white or cream back
D Rezyklierter mit grauer Rückseite, recycled with grey back

 

Test methods

General

This section contains an alphabetical list of the tests by which paperboard is evaluated during manufacture. The list is divided into two parts:

  • Paperboard property tests
  • Extrusion/lamination property tests

These test methods evaluate the board properties which influence the appearance and performance. Important test values (technical data) for the individual board products are quoted on the board data sheets in the sections Paperboard products, Plastic coatings and Foil and film laminates.

The board making process is described in the document Paperboard – the Iggesund Way, which also explains which aspects of the process are responsible for specific board properties. The Paperboard Reference Manual deals in further detail with the board properties in terms of appearance and performance, and how they influence the printing, converting and use of the board.

Paperboard property tests

All properties are measured in test climate 23°C/50% RH at the mills. Board performance properties are measured on samples taken ex board machine.

Bending

Bending stiffness, bending resistance and bending moment, see Stiffness.

Brightness

See Optical properties.

Caliper

See Thickness.

Cobb test

See Water absorption.

Colour

See Optical properties.

Gloss

The gloss of the paperboard surface is measured in accordance with ISO 8254-11). The gloss is expressed in % units. The surface of the board is illuminated at an angle of 75° and the reflection from the surface is recorded by a photo-electric cell.

Within Holmen Iggesund a surface having a measured value
< 40% board gloss is regarded as matt. A medium gloss board is in the range ≥ 40% to < 70%, and a high gloss board has a value of
≥ 70%.

 

1) ISO = International Organization for Standardization.

Grammage

The grammage of the paperboard is assessed in accordance with ISO 5361). Grammage expresses weight per unit area and is measured in g/m².

 

1) ISO = International Organization for Standardization.

Ink absorption

Ink absorption is measured using an internal test method. The ink absorption is expressed in % units. A specific ink is applied to the paperboard surface. The amount of ink absorbed in a given time is assessed by % reflectance compared with the unprinted surface. Porométrique ink No. 3809 from Lorilleux is used for the testing of ink absorption.

Interlayer strength

See Ply bond.

Moisture content

The absolute moisture content is measured in accordance with ISO 2871). It is expressed in % of the paperboard weight. The moisture content of the board is measured continuously on line on the board machine and recorded.

 

1) ISO = International Organization for Standardization.

Opacity

The opacity of the paperboard is assessed in accordance with ISO 24711). The measuring principle is based on comparison of reflectance for a single paperboard sheet over a black background compared to an opaque pack of paperboard samples. Opacity is expressed in % units and readings close to 100 mean no show through.

 

1) ISO = International Organization for Standardization.

Optical properties

The term whiteness is often used as a comprehensive expression for some of the optical properties of the surface of paperboard, although whiteness is also a specific value that is measured today. The properties quoted here are CIE-whiteness, Brightness and Colour.

Where paperboards include fluorescent whitening agents or FWA’s (sometimes referred to as optical brightening agents or OBA’s) measurements are made using an illuminant that contains a controlled element of ultra violet (UV) light.

All values are measured at both Iggesund Mill and Workington using Datacolor Elrepho instruments.

Optical properties, CIE-whiteness

CIE-whiteness (W) is a comprehensive term used to express the visual impact of near white surfaces by means of a single value.

This value, based on CIE (Commission Internationale de l’Eclairage) tristimulus values, describes perceived whiteness in outdoor UV-rich illumination. A large number of equations have been developed to calculate whiteness, but CIE-whiteness is perhaps the most commonly used. CIE-whiteness is measured in accordance with ISO 114751).

 

1) ISO = International Organization for Standardization.

Optical properties, ISO Brightness

This is the diffuse blue reflectance factor measured at an effective wavelength of 457 nm. As the measurement is only carried out in the blue region of the spectrum it is of limited usefulness.
ISO Brightness is measured in accordance with ISO 24701).

 

1) ISO = International Organization for Standardization.

Optical properties, Colour

To quantify the impression of colour to the human eye of a nearly white surface, the CIE colour space can be used. Three reflectance figures L*, a* and b* known as the CIELAB coordinates are measured using a standard light source.

The coordinates a* and b* measure colour. Positive figures for a* express redness, negative figures greenness, and positive figures for b* express yellowness, negative figures blueness. L* is a percentage which measures luminance on a scale where black is zero and pure white is usually 100%. Colour is measured in accordance with ISO 5631-21).

optical properties of colour

 

1) ISO = International Organization for Standardization.

Ply bond

The interply or interlayer strength of the paperboard is measured in accordance with TAPPI 5691). Ply bond is measured using a Scott Bond type tester and is expressed in J/m2.

 

1) TAPPI = Technical Association of the Pulp and Paper Industry.

Smoothness

See Surface roughness.

Stiffness

A number of methods of measuring stiffness are recognised. Values for the following methods are quoted in this catalogue:

  • Bending stiffness L & W 5°
  • Bending resistance L & W 15°
  • Bending moment Taber 15°

Since the stiffness is related to the orientation of fibres in the sheet during manufacture, two values are given: For the machine direction (MD) and the cross direction (CD).

Stiffness, Bending stiffness L & W 5°

Bending stiffness L & W 5° is measured in accordance with ISO 56281), DIN 53 1211). The bending stiffness is expressed in mNm.

 

1) ISO = International Organization for Standardization.
    DIN = Deutsche Industrie-Norm.

Stiffness, Bending resistance L & W 15°

Bending resistance is measured in accordance with ISO 24931).
The bending resistance is expressed in mN.

 

1) ISO = International Organization for Standardization.

Stiffness, Bending moment Taber 15°

Bending moment is measured in accordance with ISO 24931). If the bending moment is expressed in mNm, the following relationships apply:

  • Bending moment (Taber 15°) = Bending resistance (L & W 15°) x 0.0483
  • Bending resistance (L & W 15°) = Bending moment (Taber 15°) x 20.70

Note: If Taber is expressed in gcm the following conversion applies:

  • Taber in mNm = Taber in gcm x 0.0981.

 

1) ISO = International Organization for Standardization.

Surface pH

Surface pH is measured on a water extract. It is expressed in pH units on a scale of 0 –14.

illustration of surface pH value

The pH scale.

Surface roughness

Surface roughness is measured in accordance with ISO 8791-4, using the Parker Print Surf Roughness tester (PPS) at 1000 kPa using a soft backing (S10). The surface roughness is expressed in μm. Lower results indicate smoother surfaces.

Uncoated surfaces are measured using the Bendtsen method and the roughness is expressed in ml/min. Lower results indicate smoother surfaces.

Surface strength

The surface strength is measured in accordance with ISO 37831). The strength is expressed in m/s. This test evaluates the ability of the surface to withstand picking and blistering and is carried out using an IGT Printability Tester using a medium viscosity oil. Where strength is expressed in N/m the following correlation applies.

illustration of the relation between IGT values

Relation between the unit of measurement for IGT-values.

 

1) ISO = International Organization for Standardization.

Surface water absorption

See Water absorption.

Taint and odour

Taint and odour is assessed by members of trained panels assigning numerical ratings and recording their impressions of tainting flavours or volatile smells experienced. All our paperboard products are tested by the Robinson taint test based on DIN 10 9551).

GC (Gas Chromatographic) and Mass Spectrometer methods are used for assessing and identifying paperboard components and those arising from printing and conversion processes.

Our laboratory for sensory and chemical analyses is accredited for sensory analyses with the accreditation number 1740. Accredited laboratories are appointed by the Swedish Board for Technical Accreditation (SWEDAC). The Swedish accredited laboratories meet the requirements laid down in the European standards EN 45001, and EN 45002 as well as their international equivalent ISO/IEC Guide 25.

 

1) DIN = Deutsche Industrie-Norm.

Tearing resistance

The measured force required to tear a paperboard sheet is given for machine direction (MD) and cross direction (CD) respectively. Tearing resistance is measured in accordance with ISO 19741) and is expressed in mN.

 

1) ISO = International Organization for Standardization.

Tensile strength

The tensile strength is the force required to rupture a strip of paperboard. Values are given for machine direction (MD) and cross direction (CD) respectively. The tensile strength is measured in accordance with ISO 1924-21) and is expressed in kN/m.

 

1) ISO = International Organization for Standardization.

Thickness

The paperboard thickness is measured in accordance with ISO 5341). The thickness is expressed in μm. Caliper (pts) is also recorded for reference on specification sheets, where pts are inches/1000.

 

1) ISO = International Organization for Standardization.

Water absorption, Cobb test

The surface water absorption is measured using the Cobb test in accordance with ISO 5351). The water absorption is expressed in g/m².

 

1) ISO = International Organization for Standardization.

Water absorption, Wick test

Water absorption at the paperboard edge is measured using a Wick test. The paperboard surface is sealed with waterproof tape on both sides. The sample is weighed, placed in water at 80°C for 20 minutes and reweighed. The amount of water absorbed by wicking is expressed in kg/m².

Whiteness

See Optical properties.

Wick test

See Water absorption.