Chemithermomechanical Pulp Research Articles

Use of wood fibers in thermoplastic composites: VI. Isocyanate as a bonding agent for polyethylene–wood fiber composites

AbstractLinear low density (LLDPE) and high density (HDPE) polyethylenes were reinforced with wood fibers of aspen chemithermomechanical (CTMP) pulp. The different isocyantes: (i) polymethylene (polyphenyl isocyanate), (ii) tolene –2–4‐diisocyanate, (iii) 1–6 hexamethylene‐diisocyanate, and (iv) ethyl isocyanate used as bonding agents improved the tensile properties of the composites. HDPE performed better in comparison with LLDPE composites. Also, shorter fibers (mesh size 60) produced higher tensile strength and modulus in HDPE. The comparison of HDPE reinforced with aspen, mica, and glass fibers showed the effectiveness of wood fibers in terms of their cost and performance.

Grafting of vinyl monomers onto wood fibers initiated by peroxidation

The oxidation of chemithermomechanical (aspen) pulp with ruthenium tetroxide followed by peroxidation with hydrogen peroxide was performed to study the graft copolymerization of methacrylic acid, epoxypropyl acrylate and epoxypropyl methacrylate. For epoxy monomers, lower pH (i.e. < 5) is more favorable due to the participation of the epoxy group in the grafting reaction in acidic medium. Moreover, the grafting of epoxy monomers appeared more efficient than methacrylic acid.

THE XANTHATE METHOD OF GRAFTING ΧIIΙ. EFFECT OF COMONOMERS ON THE GRAFTING OF METHYL ACRYLATE ONTO WOOD PULP

Attempts have been made to discover the effect of different variables, such as initial pH, concentration of H 2 O 2 and monomer, reaction time and temperature, as well as the effect of comonomer, e.g. styrene or acrylonitrile on the grafting parameters of methyl acrylate onto chemithermomechanical pulp (hardwood-aspen)

Singlet-oxygen-induced bleaching of high yield pulp sheets

Sheets of stone groundwood (GW) and chemi-thermomechanical (CTMP) pulps made of spruce have been treated with singlet oxygen generated using the microwave discharge technique. The results show a small but distinct bleaching effect which was larger for GW than for CTMP sheets and also larger for sheets aged by storing in the dark and for sheets artificially aged by UV-visible radiation than for fresh sheets. Because only a small fraction of the oxygen was excited to the singlet state by the microwave discharge the bleaching effect of singlet oxygen was further verified by comparison with tests done under autoxidative conditions. The bleaching was partly counteracted by the thermal aging occuring during the singlet oxygen treatment.

Mechanical Properties of Cellulose Fibers Reinforced Thermoplastics

Cellulose fibers are selected as a reinforced filler for thermoplastics due to their superior mechanical properties and lower price compared to the thermoplastics. In the present study chemithermomechanical pulp of hard wood (aspen) fibers having selected aspect ratio (length/diameter) were first encapsulated with polystyrene and then mixed with polystyrene polymer at various concentrations. Mechanical properties were measured on compression molded samples containing between 10 and 40 weight percent of cellulose fibers. Experimental results show a signifi cant increase in tensile stress and modulus with fiber concentration. Using the constituent properties, an efficiency factor of stress transfer between fiber and polymer matrix was calculated and was shown to be constant for the various fiber concentrations. Theoretical predictions of tensile stress and modulus using the basic composite theory have been made. Large differences between experimental results and theoretical predictions have been observed and will be discussed in terms of fiber orientation and fiber aspect ratio.

広葉樹ＣＴＭＰの製造 Ｉ サルファイト系前処理ＣＴＭＰの物理的特性

A study has been carried out to determine the influence of chemical pretreatments on the physical properties of chemithermomechanical pulps (CTMP) made from hardwood chips which were chemically treated with sulfite liquors at the range from pH 1.8 to 13.0.Of the chemical pretreatments investigated, neutral sulfite (pH 9.8) and bisulfite (pH 4.1) appeared to offer the greatest potential for strength development to produce CTMP from hardwood chips. Alkaline sulfite (pH 13.0) and acid sulfite (1.8) treatment, on the other hand, have little effect on the strength properties of CTMP.As far as energy requierment is concerned, pretreatment with sulfite liquor at low pH (4.11.8) leads to a substantial reduction in refining energy. However, there are distinct differences in the long fiber contents between acid sulfite CTMP and bisulfite CTMP. In the case of acid sulfite-and bisulfite-pretreatments, The strength properties of CTMP from birch wood were higher than those of CTMP from oak wood.The ultraviolet microscope was used to follow the delignification visually during acid sulfite-and bisulfite-pretreatment of birch wood. When the birch wood was delignified with bisulfite, the topochemical effect was not detected, while topochemical preference for the removal of lignin from the secondary wall was found in the case of acid sulfite-pretreatment.Furthermore, it was found that total pore volume and median pore width of cell wall treated with bisulfite was larger than that of cell wall treated with acid sulfite.

Anaerobic Treatment of Sulphur-Containing Effluents

A new method of defibring wood chips and producing chemi-thermomechanical pulp with significant capital and energy savings has been developed. The pollution load of bleached CTMP effluent varied between 40-60 kg/t for BOD5 and 120-210 kg/t for COD. The process includes a sulphite stage and the effluent contains sulphur compounds which are toxic to methanogenic bacteria. Studies have been conducted on anaerobic fixed bed reactors with upflow or downflow feed modes. It is necessary to progressively acclimate bacteria to increasing concentrations of sulphur compounds. Permanent functioning of reactors is possible with COD/S ratios near 10-12 where propionate concentrations are increasing. Upflow reactors are more efficient than downflow reactors, with a maximum loading rate of 3.5 kg COD/m3.day corresponding to 800 mg/l as S. With hybrid sludge bed/fixed bed reactors it is possible to enhance anaerobic treatment efficiency. A COD loading rate of 4.7 kg/m3.day can be maintained with a residence time of 2 days and a pollution load removal efficiency of 45% for COD (55% with complementary oxidation) and 70% for BOD5. The economics of effluent treatment give an investment cost of about 20 US$/ADt for the activated sludge process and 12.5 US$/ADt for anaerobic fixed bed treatment.

The xanthate method of grafting. X. Grafting of acrylamide onto very-high-yield chemithermomechanical birch and aspen pulps

Hardwood pulp (birch: Betula Papyfera Marsh, and aspen: Populus Tremolides Michx) has been copolymerizeed with acrylamide using the xanthate grafting method. Grafting has been initiated using a redox system of ferrous ion and hydrogen peroxide. The effect of operating conditions on grafting parameters was also investigated. The factors studied were initial pH, time, and concentrations of hydrogen peroxide and acrylamide. When birch was used as a substrate, grafting parameters were as follows: grafting efficiency 82%, degree of conversion 35%, and polymer loading 60%. In the case of aspen, the maximum level of grafting efficiency, i.e., 87%, was reached with a polymer loading of 60%. Nevertheless, as in the case of birch, the conversion reached a rather low-level reading, i.e., 50%. Finally, some mechanical properties of paper sheets obtained through grafted pulps (dry and wet breaking lengths, dimensional stability, modulus, and extension at break) are compared to those of standard paper sheets.

ジャイアント・レウカエナ材のＣＴＭＰの強度と繊維特性

The fiber characteristics (fiber length, specific surface area, etc.) of alkaline sulfite chemithermomechanical pulp (Na2SO3+NaOH-CTMP) obtained from Giant Leucaena wood were measured and compared with those of thermomechanical pulp (TMP) and chemithermomechanical pulp (Na2SO3-CTMP).The weighted average fiber length of Na2SO3+NaOH-CTMP was 0.75mm, which was longer than those of TMP (0.53mm) and Na2SO3-CTMP (0.55mm).The specific surface area increased in the order TMP (4.5m2/g)<Na2SO3-CTMP (5.2m2/g)<Na2SO3+NaOH-CTMP (7.8m2/g). The large surface area of Na2SO3+NaOH-CTMP can be ascribed to the formation of fibrils and films-like particles on the fiber surface. The degree of internal fibrillation was higher in Na2SO3+NaOH-CTMP than in TMP or in Na2SO3-CTMP.The high sheet strength of Na2SO3+NaOH-CTMP can be explained on the basis of the development of internal and external fibrillation by the addition of NaOH.

Use of grafted aspen fibers in thermoplastic composites: IV. Effect of extreme conditions on mechanical properties of polyethylene composites

AbstractHardwood fibers of aspen in the form of chemithermo‐mechanical pulp (CTMP) have been used as reinforcement in linear low density polyethylene (LLDPE). The effect of composite treatment (immersion in boiling water, heat exposure at 105°C for seven days or at a temperature of −40°C) on resulting mechanical properties were evaluated. The grafted aspen CTMP composites showed by far the best results with regard to secant modulus, tensile strength, energy, and strain when compared to those of wood flour, mica or glass–fiber filled LLDPE, as well as to virgin LLDPE. Finally, the dimensional stability of CTMP aspen‐filled LLDPE composites immersed for four hours in boiling water was better than that of mica or glass–fiber filled LLDPE.

Use of wood fibers in thermoplastic composites II: Polyethylene

AbstractWood fibers of aspen in the form of chemithermomechanical pulp (CTMP) has been used as reinforcement in polyethylene (PE). The secant modulus, tensile strength, energy, and elongation at yield were measured. It was found that the mechanical properties of the composite were higher than those of PE by a factor of 2.6 for modulus, 2.3 for stress, and 2.1 for energy at yield. Compared to glass fiber composites, the CTMP composites showed higher elongation, about 100 percent higher energy, 106 percent higher stress, and 75 percent higher modulus. Note that the cost of treated wood fibers is several times lower than that of treated glass fibers.

Anaerobic Treatment of Wastewater from the Production of Chemi-Thermomechanical Pulp

The anaerobic treatment of waste water from the production of peroxide-bleached chemi-thermomechanical pulp was studied. Hydrogen peroxide had to be removed from the waste water before treatment in a methane producing reactor was possible. Peroxide in concentrations up to 200 mg/1 could be removed from the waste water by means of degradation in an acidogenic reactor, the first stage in an anaerobic two-stage process. A system consisting of a prestage and a subsequent acidogenic reactor could successfully remove peroxide in a concentration of 1200 mg/l from the waste water. The prestage was continuously fed with sludge from the acidogenic reactor. The redox potential in the acidogenic stage of a two-stage process proved to be a valuable control parameter when treating waste water containing peroxide. Adaptation of the methanogenic microflora to inhibitory compounds in the waste water was possible. Treatment of the waste water in a pilot plant at low loading rates gave a COD reduction of 50-60% and a methane yield of 0.3 Nm3/kg COD reduced.

Chemithermomechanical pulping of white birch for newsprint

The main objective of the study was to investigate the mechanical pulping characteristics of white birch (Betulapapyrifera Marsh.) by a chemithermomechanical process using NaOH and Na2SO3 in the pretreatment of chips prior to pressurized refining. The results indicated that the NaOH had significant effect upon the pulp quality, whereas the Na2SO3 was of limited importance. Chemithermomechanical pulp of white birch was further found to be suitable for at least partial replacement of high-cost chemical pulp component, customarily added to newsprint furnishes, without lowering of paper properties.

The strength properties of pulps from red lauan produced by different pulping methods.

This investigation was carried out to study the effects of various chemical pretreatments and different chemical pulping methods on the strength properties of corresponding chemithermomechanical pulp (CTMP) and chemical pulps from red lauan.In CTMP, chips were pretreated with cold soda, hot soda, alkaline sulfite, bisulfite and neutral sulfite prior to fiberization. The strength properties of CTMP increase in the order of cold soda<hot soda<alkaline sulfite<bisulfite<neutral sulfite pretreated chips.In chemical pulping, chips were cooked by means of the following cooking methods: kraft, alkali-methanol and cresol-water pulping. It showed that at the cooking temperature 170°C, there was no difference between the strength properties of alkali-methanol and kraft pulps except tear factor. The cresol-water pulping on the other hand, produced pulps with inferior strength properties but more effective in dissolving alcohol-benzene extracts compared to those of the alkali-methanol and the kraft pulping.

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