Showing papers in "Appita Journal in 2001"

Papermaking quality of fines from different pulps - the effect of size, shape and chemical composition

Abstract: The fines of chemical pulps have a strong tendency to intensify the interaction between fibres. This is mainly due to the increased density of the network. A sheet made of kraft fines has a remarkably high density, 1100 -1200 kg/m3, whereas a handsheet made of TMP fines has a rather low density, about 450 kg/m3. In this study several pulps were compared. The fines form a spectrum ranging from fines of bleached softwood kraft to the fines of mechanical pulp. The differences between softwood and hardwood kraft fines as well as between bleached and unbleached softwood kraft fines are rather small. Clearly larger differences are within the different fractions of a fines from a certain chemical pulp. In addition to the size of the fines particles the shape seem to be important factor. Only part of differences in the quality of the fines can be explained by the chemical composition. But the results indicate that the size shape and chemical composition of the fines fraction have inter-correlation.

Development of a process for the production of dissolving kraft pulp using xylanase enzyme

Abstract: A process has been developed for the production of dissolving kraft pulp employing an enzymatic pretreatment with xylanase enzyme. Specifically, this process consists of using a mild prehydrolysis stage to leave a high pentosans content in the unbleached pulp. The increase in pentosan content in the unbleached pulp, from mild water prehydrolysis and kraft cooking, results in increased unbleached pulp yield at the same Kappa number compared to conventional prehydrolysis kraft. Bleaching of this high pentosan pulp with a high dose of enzyme and CEHED bleaching, results in the desired level of pentosans in the final pulp (2.4 to 2.6%), a reduction in bleach chemical requirement, improvement in the brightness of the final bleached pulp by about 2 percentage points, and a significant increase in the bleached pulp yield as compared to the control (regular prehydrolysis, kraft cooking, CEHED bleaching). The yield improvement is about 2.5%. Also, the rayon yield and reactivity are higher in the case of enzyme treated pulp.

Provenance effect on wood chemical composition and pulp yield for Eucalyptus globulus labill

Abstract: The chemical composition and pulping yield of Eucalyptus globulus wood was determined for 7-year-old trees from 37 provenances from subspecies globulus, bicostata and maidenii, grown on one site, using cores taken at breast height. The chemical composition and pulp yield varied with provenance and with subspecies. Total extractives ranged 1.9% to 7.3%, total lignin averaged 29.8% (23.6 to 46.4%), glucan content was 42.8% (36.2 to 49.3%), and xylan content 23.9% (19.6 to 28.1%). The mean pulp yield was 51.0% (46.8 to 53.3%) with an average 2.9% residual lignin in the pulp. The subspecies maidenii was chemically different from subspecies globulus, showing higher extractives and lignin contents, and lower glucan content. The subspecies globulus showed pulp yields 1 to 3% above bicostata and maidenii. Pulp yield was negatively correlated with the extractives content but not with lignin, glucan and xylan. The between-provenance variability in relation to chemical and pulping parameters indicates the selection potential of this species.

Variation of fibre biometry in different provenances of Eucalyptus globulus Labill

Abstract: The fibre biometry of Eucalyptus globulus was measured in 7-year-old trees from 37 provenances grown on two sites, using cores taken at breast height (b.h.). Measurements were made at different radial positions (10%, 30%, 50%, 70% and 90% of total radius) and a mean fibre length for the cross-section was calculated as an area-weighted average. The mean fibre length was significantly influenced by provenance and very significantly by site, with a range of variation between 0.78 and 1.05 mm for one site and 0.92 and 1.03 mm for the other. A strong radial variation of fibre length was found in all cases, with an increase from pith to bark. Fibre width and wall thickness ranged 15.8 to 22.2 pm and 3.8 to 5.8 pm on one site and 14.5 to 20.0 pm and 4.2 to 5.8 pm for the other. The variation in fibre cross-sectional dimensions was not significantly influenced by provenance.

Soda-AQ pulping of wheat straw

Abstract: Delignification of wheat straw was carried out by conventional soda-AQ pulping under varying conditions to determine the relationships between selected cooking variables (EA, 12 to 18%; maximum temperature, 145 to 165°C; time to maximum temperature, 70 to 110 min; and time at maximum temperature, 0 to 30 min) and pulp properties (yield, Kappa number, and viscosity). EA, maximum temperature, and time at maximum temperature affected pulp yield and Kappa number with almost equal intensity, whereas maximum temperature and time at maximum temperature both had a significant effect on pulp viscosity. Contrary to wood-based pulping, the viscosity of wheat straw pulp increased as the Kappa number fell.

Application of NIR Spectroscopy to Clonal Eucalyptus globulus Samples Covering a Narrow Range of Pulp Yield

Abstract: The application of near infrared (NIR) spectroscopy to clonal Eucalyptus globulus, that cover a narrow range of pulp yields, is described. Experiments were conducted with two clones grown on three different sites. Several pulp yield calibrations were developed, with yield ranges between 5.0 and 3.1 units of yield. The same spectral data were used to develop calibrations for basic density and pulpwood productivity. The success of the calibrations demonstrate that NIR spectroscopy can provide sufficiently precise data to be useful over the narrow range of pulp yields encountered in pulpwoods from tree improvement programs provided the primary yield data is accurate.

Longitudinal density variation in irrigated hardwoods

Abstract: Nine hardwood species, comprising six eucalypts, two acacias and a casuarina, were sampled from a 6-year-old plantation trial at Bolivar, 20 km north of Adelaide in South Australia. For the eucalypts, the predominant trend was for a reduction in density from the base of the stem to 10% of total tree height, followed by a progressive increase in density thereafter. However, in one seedlot of Eucalyptus grandis, and in E.botryoides, Acacia melanoxylon and A.mearnsii, the overall trend was for a reduction in density with tree height. It was concluded that prediction of whole-tree mean basic density from a single disc sample would only be reliable if models specific to individual species and seedlots were used. Moreover, because the correlations between the whole-tree mean density and that of single disc samples were lower at the top and bottom of the tree, these levels should be avoided as density sampling positions.

New water-based barrier coatings for paper and paperboard

Abstract: Results obtained with new water-based barrier coatings for paper and paperboard are presented. These coatings include polyester-based coatings, dispersions containing hydrophobic monomers and coatings made from biodegradable polymers. Coatings were tested as such, some were filled with talc and some were used as an additive in a commercial polymer dispersion. Relatively good barrier values were achieved. However, work needs to be done to optimise the properties of biodegradable polymers for water-based coatings. The object of this study was also to compare different fillers and additives in water-based barrier coatings. The coating performance can be controlled by a suitable choice of fillers. Folding of filled coatings destroys the barrier due to pinholes and cracks. Certain additives can improve the barrier performance of the coatings ; however, filler type and filler addition level are often the dominating factors as far as barrier properties are concerned.

On the distributions of mass, thickness and density in paper.

Abstract: Data are presented from exptl. measurements of the local grammage and thickness made on lab. formed paper sheets with a range of structures. It is obsd. that the distributions of local grammage and local thickness are strongly correlated. The correlation between the variances of thickness and grammage are dependent on pulp type, but independent of mean sheet grammage, whereas the correlation between their coeffs. of variation is independent of pulp type and dependent on mean sheet grammage. Also, correlation is shown between the variance of local d. and that of grammage, and this is sensitive to mean grammage. However, the variance of local d. is independent of the variance of local thickness. The coeff. of variation of local d. is correlated to the coeffs. of variation of local grammage and thickness; the correlations being sensitive to pulp type and apparently dominated by the properties of high coarseness fibers in a blended furnish. Also, it is noted that the mean d. of sheets contg. high coarseness fibers increases with improved formation. [on SciFinder (R)]

Silvichemicals from pulp mill wastes: biosorption of metal ions on ellagic acid

Abstract: A pipe deposit waste containing metal complexes of ellagic acid from a pulp mill was pretreated by an optimised purification method to break down the complexes to ellagic acid and then examined for its capacity to sequester the heavy metals Cu(II), Cr(III) and Zn(II) from dilute aqueous solutions. Pretreatment with HCl of various concentrations resulted in different purities of ellagic acid and adsorption capacities for Cu(II), ranging from 5.4 to 6.2 meq/g o.d. biomass, which were higher than that of a commercial ellagic acid sample. The uptake of copper, zinc and chromium on the purified ellagic acid waste was optimal at different solution pH conditions (4 to 7), indicating its promise for selective metal separations. Biosorption of chromium was reasonably rapid, reaching more than 95% of the final uptake value within the first 2 hours of contact. The Langmuir isotherm model was suitable for describing the metal adsorption for all the ellagic acid samples tested. The purified ellagic acid wastes, and commercial sample, were characterised by 1 H NMR spectroscopy and scanning electron microscopy in order to help clarify the observed variations in adsorption performance.

Effect of irrigation on growth and fibre quality of Eucalyptus globulus and Eucalyptus nitens

Abstract: An experiment in southern Tasmania provided an opportunity to study the impact of continuous irrigation or cycles of drought stress on growth and wood quality of Eucalyptus globulus Labill. and Eucalyptus nitens (Deane and Maiden) Maiden. These species are commonly planted for pulpwood production in southern Australia. Growth was measured over a 6-year period and fibre quality assessed at age 6 years. Height of E.globulus was greater than that of E.nitens irrespective of water status. In the irrigated treatment diameter increment was greater in E.nitens than E.globulus in the third year of growth. Annual increments in stem volume were greater in E.globulus than E.nitens during the first 5 years. The effects of drought stress were more apparent in E.nitens than E.globulus. Irrigation led to lower basic density, longer average fibre length in E.nitens, lower fibre coarseness in E.globulus, and better strength properties when tested for cold caustic soak chemimechanical pulping characteristics.

A simplified approach to understanding the mechanism of AKD sizing

Abstract: Alkyl ketene dimers (AKD) are widely used in the sizing of paper products. It is generally accepted that during curing, AKD redistributes on the surface of the fibres via migration. Although AKD redistribution on the surface of cellulose fibres has been studied, the mechanism that dominates AKD redistribution has not been fully understood. In this laboratory we attempted a simplified approach for studying the mechanism of the redistribution of AKD. Work presented in this paper is the first part of this investigation in which we sought the answer to the question of whether AKD spreads in the absence of capillary action. For this purpose a glass surface was used as a hydrophilic substrate and the behaviour of AKD wax during the curing process was monitored. Our results suggest that AKD does not undergo spontaneous flow-like spreading on glass surface. Curing causes areas of glass surface that were initially not covered by AKD wax to gain a weak sizing effect. It is most likely that the weak sizing effect of these areas is caused by the deposition of either AKD vapour or other volatile materials in the wax. Our results also show that the AKD-sized glass surface is very non-uniform but this does not prevent the sized glass surface from exhibiting a good macroscopic sizing effect.

Cationic starch as a dry strength additive for bleached Eucalyptus globulus kraft pulps

Abstract: Paper sheets, filled with calcium carbonate, and made with bleached Eucalyptus globulus kraft pulps (refined to 40°SR, ∼270 CSF) were prepared in the presence of several cationic starches (CS), as dry strength additives. Six cationic starches having different degrees of substitution (DS), namely: 0.017, 0.022, 0.034, 0.047, 0.06 and 0.09 and 3 levels of addition, i.e. 0.5, 1 and 2% CS with respect to oven dried pulp, were used. It was found that internal cohesion strength and burst index were the parameters most sensitive to the presence of CS, increasing by up to 80 and 50%, respectively, for paper made with 2% CS having a DS of 0.034. Cationic starches with DSs of 0.047 and 0.06 also gave very good results. As expected, filler decreased the overall mechanical properties, i.e. tensile and burst indexes, internal cohesion strength and elongation. The use of CS with a DS equal to 0.034 compensated for the decrease in paper properties induced by the use of calcium carbonate filler.

APMP pulps from non-wood fibres. Part 1: kenaf and straw

Abstract: Results from the present investigation have demonstrated that using alkaline peroxide pretreatment followed by refiner mechanical pulping, both kenaf and straw fibres may be converted into pulps having strength properties comparable to aspen APMP or market BCTMP pulps. Kenaf fibre was relatively easy to bleach, and its APMP pulps have higher tensile strength at the same handsheet density, or higher bulk at the same tensile strength, than aspen APMP pulps. This comparison suggests that kenaf APMP pulps have potential for applications similar to aspen APMP or market BCTMP, which is currently used in printing/writing, tissue and high brightness paperboard grades. Compared to kenaf, straw was more difficult to bleach. Because of this, application potential of straw APMP pulp is limited to low brightness grades such as newsprint and low brightness paperboard.

Kinetics of chlorine dioxide delignification of a hardwood kraft pulp

Abstract: The kinetics of chlorine dioxide prebleaching (D o ) of a Eucalyptus globulus kraft pulp was investigated. A kinetic model for this stage is proposed based on experimental monitoring of Kappa number, chlorine dioxide concentration and temperature trends with reaction time. The model predicts the Kappa number after the D o stage and the chlorine dioxide concentration. A set of two new parameters, K θ and [ClO 2 ] θ are introduced to enable the use of a homogenous model. A non-linear relationship between chlorine dioxide consumption and the decrease of Kappa number, which is independent of temperature in the range of 5°C to 70°C, has also been established. Moreover, the floor Kappa number is identified as a strong linear function of temperature. The fit of the experimental results is very good and the validation of the model reveals its excellent prediction capabilities for both Kappa number and chlorine dioxide concentration in a D o stage.

Modified kraft pulping to high Kappa numbers

Abstract: The influence of modifications to the kraft process on the cooking selectivity and strength properties of the pulp has been studied in the high Kappa number region. Three different process modifications were investigated: Modified Continuous Cooking (MCC), Isothermal Cooking (ITC) and Modified Batch Cooking. The results show that no improvements were obtained by these modifications. It is however important to note that the cooking conditions for modified kraft pulping to low Kappa numbers were applied to the higher Kappa number region without optimisation of the cooking conditions. The results also demonstrate that it is always an advantage to decrease the cooking temperature. A lower cooking temperature is beneficial for pulp yield, amount of rejects and pulp viscosity. If the cooking temperature is too high, the pulp quality may be affected negatively.

Dimensional relationships among radiata pine wood tracheid, and chemical and TMP pulp fibres

Abstract: Softwood tracheid and pulp fibre dimensions can be indicators of the quality of a pulp and its suitability for use in the manufacture of specific paper products. There is a need to be able to use wood tracheid and/or pulp fibre dimensional data in the assessment of pulp qualities and processing effects, and ultimately in the production of designer fibres for specific product types and end uses. In this paper softwood fibre cross-section dimensions are shown to be strongly influenced by the pulping process used, chemical and structural organisations within fibre walls, and the procedures used to prepare pulps for fibre measurement. Furthermore, latewood (but not earlywood) kraft fibre wall areas and wall thicknesses (but not perimeters) show high levels of variation when compared to those of corresponding wood tracheid, and TMP fibre properties, indicating different chemical and/or structural wall organisations for some fibres in latewood fibre populations.

Effect of Primary Fines and Surface Charge of Hardwood Pulps on AKD Sizing

Abstract: The printing properties of paper are strongly dependent on the wettability of fibres in the sheet structure. Chemicals, referred to as sizes, are usually added to such papers to slow the rate of liquid penetration as untreated papers are very hydrophilic. When writing paper is produced under alkaline conditions, alkyl ketene dimer (AKD) is frequently used as the size to modify wettability. The rate of penetration of a liquid into paper depends, amongst other factors, on the amount of sizing agent which is on the fibre surface. This depends on the concentration of the sizing agent added to the fibre suspension and the percentage which is retained on the fibres. In this work we sought to gain a greater understanding of the effect of primary fines and surface charge on sizing by studying four hardwood kraft pulps, an unbleached eucalypt, a bleached eucalypt, a bleached birch and a bleached tropical hardwood, with 0.1% AKD added in the form of a commercial emulsion. No separate retention aids were added. The effect on sizing of the removal of fines (material passing 200 mesh) prior to sheet forming was also examined. Wood pulp fibres produced either by mechanical means or by chemical treatment carry a negative charge. Positively charged material can be retained through attraction to these negative charges. The surface charge on the pulps was determined by polyelectrolyte titration. The degree of sizing was measured by Contact Angle and Cobb tests. The surface charges on the fibre component of the four pulps were similar but differences in fines content and the surface charges on the fines resulted in significant differences in the surface charges on the whole pulps. The degree of sizing was similar for all sheets except those formed from tropical hardwood pulp fibres (fines free) and from the bleached birch pulp. The results are consistent with the degree of sizing being strongly influenced by surface charge but with the fines having an influence which is not simply related to their contribution to surface charge.

Modelling water removal from wet fibre mats

Abstract: During vacuum dewatering on papermachines, the wet fibre mat is subjected to high frequency suction pulses. These pulses result in the wet fibre mat compressing as well as water being displaced from the pores with air. Laboratory results have indicated that the suction pulse length and suction pulse frequency can have a significant effect on the final solids content after application of suction. In order to understand the process occurring during vacuum dewatering a one dimensional two phase flow model was developed. The effect of process variables and wet fibre mat properties have been investigated.

Between species differences in whole tree maps of fibre properties in E. nitens and E. globulus -utility of control deviation charts to assess optimal sampling height

Abstract: One each well-formed E. nitens and E. globulus tree, 13.8 m and 15.4 m in height respectively, were destructively sampled with discs cut at nine percentage heights (5,10,20,…,80%). Intense within-ring sampling and measurement of fibres provided whole tree maps of variation of fibre dimensions and allowed whole tree and area-weighted disc values to be calculated, with and without adjustment for early-wood (EW) and latewood (LW) volumes or areas (EML Adj.). Whole tree EML adjusted values for fibre length, fibre diameter, lumen diameter, wall thickness, fibre coarseness (CR), Runkel ratio (RR) and Muhlsteph ratio (MR) were similar to unadjusted whole tree values in both species. Percentage deviation of disc values from whole tree values were calculated to determine optimum sampling height (associated with minimal deviation from whole tree value of less than 5% or 10%; depending on the fibre trait). For E. globulus, optimum sampling height was 10% height (1.5 m) with a range of deviation (dev.) at this height less than 10% for all fibre dimensions. For E. nitens, optimum sampling height for fibre length, fibre coarseness, fibre diameter and lumen diameter was 10% height (1.38 m) (dev. 0.93) with whole tree values.

Within-tree variation of some wood and kraft fibre properties of Eucalyptus fastigata and E. nitens

Abstract: The variation in wood density, wood chemistry and kraft fibre properties with height position are compared for nine-tree samples from 16-year-old stands of E.fastigata and E.nitens. The shapes of the average-tree predicted models for the two species are significantly different (0.10 level) for all properties except fibre wall area (coarseness) and relative number of fibres. Some specific conclusions are : wood density and resistance to fibre collapse change only slightly with increasing height position for E.fastigata, but markedly increase for E.nitens ; kraft fibre wall thickness increases for E.nitens and decreases for E.fastigata, with increasing height position, in accordance with their similar wall areas but different perimeters. Wood glucose, xylose and lignin model-predicted means are significantly different (0.05 level) for E.fastigata and E.nitens.

Determination of paper formation by Fourier analysis of light transmission images

Abstract: Formation is the measure of variations due to non-uniform fibre distribution in a sheet of paper. Paper formation is one of the most important properties of paper and is still difficult to measure. A method for determining this property has been developed. This method, based on light transmission image analysis, uses features of the power spectrum obtained from the Fourier transform to analyse and discriminate between different floc distributions within an image of paper. The method was tested for various furnishes and showed better discrimination between different qualities of formation than the standard formation index.

Studies of fibre hemp and flax pulps as a feedstock for Australian newsprint production

Abstract: The primary aim of the pulping trials described here was to investigate the potential of using flax (Linum usitatissimum L.) and hemp (Cannabis sativa L.) bark and whole stem pulps as alternative reinforcing agents in the Australian newsprint industry. Pulps were also made from the core fraction to assess its suitability as a supplement to the short fibred eucalypt component of the existing newsprint blend. Existing cold caustic soda (CCS) and thermomechanical (TMP) pulping processes were trialed. The behaviour of the hemp core pulps was analogous to that of eucalypt except that properties developed more with chemical addition. These pulps were typically of low tear index and high tensile index. Tensile index tended to increase with the use of a higher concentration of sodium hydroxide. The flax CCS core pulps had superior tear strength but had lower tensile strength, lower brightness and were very yellow in colour compared with the equivalent CCS hemp pulp and eucalypt CCS. The properties and behaviour of hemp and flax CCS bark pulps were similar and could potentially be blended or used interchangeably. The bark fibres of hemp and flax are capable of forming paper of very high tear index but with lower tensile index and tensile energy absorption than would be desired from a softwood kraft pulp. Accurate and uniform fibre cutting would be required to overcome the tendency of the bark fibre to tangle and block screens. Whole stem pulp properties were generally intermediate to those of separate core and bark fibre.

Enzymatic hydrolysis of Pinus pinaster kraft pulp

Abstract: Kraft pulp from Pinus pinaster was treated with two enzyme preparations - Cartazyme MCX-A (which presents both cellulase and xylanase activity) and Cartazyme PS-10 (a xylanase preparation) to enhance papermaking properties of the fibres. Both preparations reduced Kappa number and improved brightness, while the effect on papermaking properties was different.

Effects of some process variables on screen fractionator performance

Abstract: Pressure screens are commonly used for shive removal and long fibre fractionation of mechanical pulps for the efficient realisation of quality targets. Disturbances in process variables can result in undesirable variations in product quality. A series of trials investigating the effect of some process variables such as fibre length distribution, inlet stock concentration, reject rate, aperture velocity and stock temperature on the performance of holed and slotted screens is summarised. The results indicate the relative importance of different process variables, and provide information useful for finding a balance between efficiency and capacity. The results also provided some insight on the mechanisms involved in the fractionation process in different screen types.

Comparison of Fracture Toughness of Paper with Tensile Properties

Abstract: The paper web runnability is significantly affected by the presence of defects in the material. Fracture toughness (FT) of paper measures its resistance to fracture from preexisting flaws and is closely related with the runnability. However, lack of rapid and reliable technique to measure the FT is a major drawback in the improvement of runnability. The aim of this work was to find any relationship between conveniently obtainable tensile properties (tensile strength, elastic modulus and Tensile Energy Absorption (TEA)) and the FT. Twelve samples were measured, from a mixture of machine made papers and handsheets. The range of FT measured by the EWF method was 8.2-28.9 Jm/kg. In this work, tensile index and TEA were both found to be linearly correlated with FT with correlation coefficients of R{2} = 0.72. However in neither case was the correlation strong enough to justify using the tensile property to predict the fracture toughness.

Characterisation of black liquors from soda-AQ pulping of wheat straw

Abstract: Wheat straw was delignified in a laboratory-scale digester by conventional soda-AQ pulping. The chemical composition of the corresponding black liquors was analysed with respect to their main organic constituents (lignin, aliphatic carboxylic acids, and polysaccharides). In addition, detailed gas chromatographic data were reported on the composition of aliphatic carboxylic acids (i.e. formic and acetic acids and different hydroxy carboxylic acids). The results showed that the dry solids of the black liquors studied contained 31 to 33% of lignin, 13 to 20% of aliphatic carboxylic acids, and 14 to 19% of polysaccharides. The value of average molecular masses (M w 4032 to 5298 Da and M n 732 to 832 Da) and polydispersity (M w /M n 5.0 to 7.1) indicated a close similarity between the dissolved lignins and a wide distribution in their molecular masses. It was also clearly noted that, beside degradation, some condensation of lignin fragments in black liquor occurred as delignification proceeded. Of the monosaccharide moieties detected, xylose was the dominant component, suggesting that xylan was a major polysaccharide constituent in the black liquor.

Single fibre fragmentation : a new measure of fibre strength loss during brown stock washing and oxygen delignification

Abstract: In this study on pulp strength loss during brown stock washing and oxygen delignification the loss in fibre strength was measured by conventional methods and by a Single Fibre Fragmentation technique (SFF). Pulp samples were collected from two Finnish softwood pulp mills; each pulp sample set was collected from a fibre plug passing through the process. The results showed that Mill 2 seemed to damage its fibres more in the brown stock area than Mill 1. Based on SFF results, and conventional strength tests, it was possible to state that this damage likely occurred between the blow tank and the last brown stock washing stage. The SFF results also indicated that the damage occurred at the fibre level. Further it was shown that latewood fibres generally are more brittle than earlywood fibres.

Effect of Mechanical Impact Treatment on Fiber Morphology and Handsheet Properties

Abstract: Alternative way of shaping fibers suitable for papermaking was introduced. Impact refining, which was done simply by hitting wet fibers with a metal weight vertically, was intended to keep the fibers from shortening and to cause mostly internal fibrillation. Virgin chemical pulp, its recycled one and ace were used in the experiment. It was noticed from the experiment that impact refining on virgin chemical pulp kept the fiber length and increased bonding properties greatly. However, in the recycled fibers from the chemical pulp, fiber length and bonding properties were decreased. In ace, which seems to contain fractions of semi-chemical pulp and mechanical pulp (GP), and which is recycled pulp from corrugated boxes, fiber length and bonding properties were decreased disastrously. We believe recycled cellulosic fibers (recycled chemical pulp and ace in this case), which went through hornification, were less resistant to the mechanical impact than virgin chemical pulp. For virgin chemical pulp, impact refining allowed no significant fiber length shortening, high WRV, and high mechanical strength.