Makes their use economically viable.

Hoglund et al. [43] have compared the same types of mechanical pulps with

Chemical pulps according to their strength properties. The mechanical pulps were

From spruce wood (SGW, RMP, TMP, and CTMP), and the chemical pulps from

Pine were either unbleached (USB) or semi-bleached (SBK). The possible property

fields for these pulps are illustrated in Figs. 7.6–7.8.

Strength properties increased in the range SGW, RMP, TMP, CTMP, USB, and

SBK. The tear resistance of CTMP pulps was close to that of unbleached chemical

Pulp USB (Fig. 7.6). The tensile index of CTMP covered large parts of the semibleached

Chemical pulp SBK and unbleached chemical pulp USB, but at lower

Apparent densities (Fig. 7.7). When considering the light-scattering coefficient,

Latency and Properties of Mechanical Pulp

Properties of Mechanical Pulp

Fig. 7.6 Tear resistance versus tensile index for various

Mechanical pulps compared with chemical pulps.

Fig. 7.7 Tensile index versus apparent density for various

Mechanical pulps compared with chemical pulps.

SGW had the highest values, followed by RMP and TMP. The light-scattering

Coefficient of CTMP was in the same range as TMP, but at higher levels of tensile

Index. The chemical pulps had the lowest light-scattering coefficient, and could be

Distinguished by type (USB or SBK) (Fig. 7.8).

Latency and Properties of Mechanical Pulp

Fig. 7.8 Light-scattering coefficient versus tensile index for

Various mechanical pulps compared with chemical pulps.

Selected properties from different mechanical pulps, made from Norway spruce

And compared at freeness level 40 mL, are listed in Tab. 7.1. General quality

Requirements of mechanical pulp for use in LWC and SCA grades are detailed in

Tab. 7.2.

Tab. 7.1 Properties of mechanical pulps for printing paper

Grades (Norway spruce, CSF 40mL).

Parameter Unit Groundwood Pressure

Groundwood

TMP

Minishives % 0.1 0.1 <0.1

Coarse fibers (R14) % 1 3 10

Long fibers (P14/R28) % 11 22 30

Fines (P200) % 38 33 30

Fiber length mm 0.65 0.85 1.5

Apparent density kg m–3 520 510 500

Gurley s 150 200 250

Tensile index Nm g–1 35 43 52

Tear index mNm2 g–1 3.2 4.2 7.2

Scott Bond J m–2 280 320 250

Light scattering coefficient m2 kg–1 75 72 60

Brightness % 65 64 62

References

Tab. 7.2 General quality requirements of mechanical pulp for use in LWC and SCA grades.

Pulp grade SGW PGW TMP TMP

Paper grade Unit SC/LWC SC/LWC SC LWC

Freeness mL 30–40 30–40 30–40 40–50

Shives content % <0.05 <0.05 <0.05 <0.05

Coarse fibers (R14) % <1.0 <1.0 <7.0 <3.0

Long fibers (P14/R28) % 10–15 14–20 28–33 22–27

Fines (P200) % >36 >32 >28 >28

Apparent density kg m–3 450–500 440–500 450–520 450–500

Tensile index Nm g–1 >40 >45 >50 >50

Tear index mNm2 g–1 >3.5 >4.5 >7.0 >6.5

Light-scattering coefficient m2 kg–1 >70 >68 >58 >58

References

Vdp Verband Deutscher Papierfabriken

E.V.

Sittauer, H.L., Friedrich Gottlob Keller,

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