A flax tow sample from China (cf. Table 1) was cooked with oxygen and alkali under various conditions. Yields and properties of the oxygen-alkali flax pulp (OAP) were compared with those of soda (AP) and neutral sulfite semichemical flax pulps (NSSCP).
Alkali charge, liquor ratio, cooking temperature, and cooking time showed significant effects on the properties of pulps obtained (cf. Fig. 1 and 2).
As to the yield and brightness of OAP, the optimum conditions without addition of MgCO
3 seemed to be as follows : 5% alkali charge on sample, 1 : 2 liquor ratio, 11O°C cooking temprature, 3 hrs. cooking time, and 7 kg/cm
2 O
2 pressure, respectively.
It was found that the addition of MgCO
3 was ineffective at lower alkali charge of 5%, but it resulted in remarkable improvement in yield, brightness, and strengths of the pulp at higher alkali charge above 5%, with selective delignification from fiber surfaces and without degradation of carbohydrate (cf. Fig. 3-6).
When compared with the pulps treated by centri-cleaner, OAP was white in color and of much higher brightness than NSSCP, and it required more bleaching chemicals to obtain the same brightness (Table 2).
Paper strengths of OAP (ex. OAP-3, 4) were compared with those of NSSCP. One of the disadvantages of OAP was lower opacity due to the increase of hemicellulose content and bonding area (Table 3 and Fig. 6).
It was shown that OAP was inferior to NSSCP from the color revertion test (cf. Fig. 7).
The color and COD of spent liquor from OAP were less than those of AP and NSSCP (cf. Fig. 8 and 9).
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