With ever increasing paper machine speed, it has become desirable to minimize the sheet moisture content at the exit of press in order to maintain higher production efficiency and higher drying efficiency.
For this purpose, elastoma cover materials for press rolls are to be kept as hard as possible and also nip pressure as high as possible, which is recent fundamental designing theme of high speed paper machine press part. This, however, constitutes a very severe condition for elastoma covered rolls and cover damages have taken place on press rolls in high speed paper machines.
The reasons of these damages are mechanical problems and elastoma cover internal heat generation by hysteresis, both of which are caused by the above mentioned condition (i.e, high nip pressure at high speed). The hysteresis problem cam not be neglected as the machine speeds become higher. This paper shows results of analysis of this problem and calculates how much power is absorbed for internal heat generation in relatoin to total press section power consumption. These calculations were made on the basis of actual operating conditions on two machines. The calculations of actual amount of internal heat generation was also made by knowing the measurable factors for power consumption.
Another investigation was performed by using experimental apparatus and a covered roll as a model at which point the generated internal heat damages the cover. It was found that the damage occurs when heat generating amount per rubber cover unit weight reaches up to 0.0840.087 kcal/kg/sec.
In case of the two machines mentioned, nip pressure were 80 kg/cm, and machine speed was 600 m/min for one and 720 for the other. The generated heat was measured to be 0.0210.024 kcal/kg/sec. So, in these two cases, thermal safety factor is 34. In a machine of this size, however, if machine speed goes up to 1, 000 m/min, heat generation radically increased to 0.044 kcal/kg/sec (safety factor : 2), which will probably causes operation and maintenance trouble for elastoma covered rolls.
Temperature distribution in the elastoma cover by internal heat generation appears higher from the surface to the inside.
I would like, however, to leave this problem as a theme to be investigated in the future.
The cover material tested in this report was polyurethane type synthetic material (hardness P & J 5).

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It was previously reported that ozone treatment of sulphate pulp waste water had lead to the very large removal efficiencies of COD (Mn) and color, and had lead to the formation of BOD components.
In this report, the mechanism of BOD removal and treatment conditions in activated sludge treatment of the ozonized liquor of diluted black liquor were studied. The results obtained were as follows.
1. The BOD removal rate was elucidated by the Eckenfelder equation, the two phase theory, and at the lower BOD concentration it was found that BOD removal was proceeded in phase II. When initial BOD was about 600 mg/l, the reaction rate of BOD removal could be expressed approximately as the first order, and when initial BOD was from 100 to 200 mg/l it could be expressed approximately as the second order.
2. BOD removal efficinecy more than 90% was achieved at less than 0.5 kg-BOD/kg-MLVSS· day, as well as that of the other pulping waste water.
3. Sludge yield was the same or less as that of the other pulping waste water. Total consumed oxygen was in the range of that of the other pulping waste water.
4. In the case of the ozonized liquor containing a few quantity of ozone (4.015 mg/l), BOD removal efficiency did not decresse at the lower BUD loading (less than 0.4 kg-BOD/kg-MLVSS· day), but it largely decreased at the higher BOD loading.
The sequential ozone-activated sludge treatment of diluted black liquor was also experimented. As a result, the total removal efficiencies of COD (Mn) and BOD were depended upon the removal efficiencies of ozone treatment and activated sludge treatment.
Even if the remaining ozone in the effluent of stirring treatment and in the gas supplied to the aeration tank were about 0.4 mg/l, 0.08 mg/l respectively, the total removal efficiencies of COD (Mn) and BOD were 61.6%, 87.5% respectively, with nearly satisfactory results.
Removal efficinecies of lignin and color were depended upon that of ozone treatment. By stirring treatment and activated sludge treatment, the concentration of two indexes reversely increased. The total removal efficiencies of lignin and color were 66.6%, 81.5% respectively.

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In order to obtain more detailed information concerning the degradation of lignin in the oxygen-alkali cooking, the milled wood lignin from Japanese red pine (Pinns densiflora) was cooked with the alkaline liquor of various pH values containing NaOH and NaHCO₃ in the presence of oxygen under the conditions shown in Table 1. The reaction mixtures thus obtained were studied for the fractionation curve of the gel filtration, UV-absorption spectrum, weak-acidic dissociation group, COD, and BOD (cf. Fig. 14 and Table 2). Furthermore, the ether-soluble fraction of the reaction products was studied by means of gas-liquid and thin-layer chromatographies (cf. Table 3 and Fig. 6). Main results are as follows :
1. When cooked the lignin with alkaline liquor adjusted to pH 13.5 in the presence of oxygen, a small amount of lignin fraction having lower molecular weight was formed even in the cooking at 70°C, and the higher the cooking temperature was, the lower molecular weight the lignin degraded into and the larger number of weak-acidic dissociation group the degraded lignin had.
2. In the case of the alkaline liquor of pH 8.5, even in the cooking at a higher temperature viz. 120 to 140°C, some of lignin having high molecular weight remained without degradation.
3. The BOD/COD ratio of the cooking mixture with alkaline liquor of pH 13.5 at a temperature of 120 to 140°C was 0.61 to 0.71, and much higher than that of the cooking mixture with the liquor of lower pH value, suggesting that lignin fraction in the waste liquor of the oxygen-alkali cooking at a high pH probably can be decomposed more easily by micro-biological treatment than can the lignin fraction in waste liquor of the ordinary alkali cooking.
4. The yields of the ether-soluble components were as listed in Table 3. Among the degradation products in the oxygen-alkali cooking with alkaline liquor of pH 13.5, methanol was in the highest yield, and acetic acid and formic acid were in comparatively high yield. It was remarkable that, in the oxydation products of the milled wood lignin, a small amount of acetone was found in addition to the aromatic and aliphatic compounds which have already been reported as the oxydation products of lignin.
The above mentioned results indicate that the degradation reaction of lignin during the oxygen-alkali cooking is markedly affected by pH value of the cooking liquor.

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