Volume 37, Issue 2

This study investigated whether the yield improvement after high alkali impregnation (HAI) is maintained after oxygen delignification and whether the potential of oxygen delignification to increase the mechanical properties is affected by high alkali impregnation. The yield improvement achieved by high alkali impregnation (1 %) was preserved after oxygen delignification, particularly of glucomannan. The total fiber charge and swelling increased after oxygen delignification regardless of the type of impregnation in the cooking step. The tensile index improvement obtained by oxygen delignification was retained if this was preceded by high alkali impregnation. The stiffness index was higher and elongation slightly lower after HAI impregnation than after a standard (REF) impregnation. Fibers obtained through high alkali impregnation seem to be slightly less deformed and slightly wider than fibers obtained after a standard impregnation.

The pulp and paper industry is increasingly seeking a sustainable and conscientious development, minimizing the environmental impacts caused by it. Therefore, reducing efficiently the number of stages used in the bleaching process can mean less consumption of water and chemical reagents, contributing to the reduction of harmful waste to the environment. Thus, this study sought to evaluate the pulp quality and some physical-mechanical properties (smoothness, tear and tensile indexes) of two new bleaching sequences A*DP and A*E*DP and compare them with the reference D 0 (E+P)D 1 P. To do so, industrial eucalyptus Kraft pulp pre-delignified with oxygen was used. The bleached pulp was refined to 1200, 1800 and 2400, in PFI mill and tested according to TAPPI standards to determine smoothness, tear and tensile indexes. Based on the results obtained, it was verified that the sequences studied are viable for using in bleaching plants, which allowed a reduction in the chlorine dioxide consumption and presented satisfactory smoothness, tear and tensile indexes for paper.

Previously it was shown that wood chip compression or enzyme impregnation prior to refining reduces energy consumption and improves pulp quality. This work characterizes the effect of different magnitudes and rates of compression on the extent of enzymatic hydrolysis. A laboratory compressor and a controlled uniaxial load set-up were used to apply different compression ratios and compression times to mixed-softwood wood chips. The chips were subsequently subjected to enzymatic hydrolysis with a high-yield exoglucanase preparation to demonstrate changes in cellulose hydrolysis. Enzymatic hydrolysis yield increased with compression ratio but was unaffected by compression time. Increasing compression ratio increased removal of soluble molecules such as sugars and acid-soluble lignin. Microscopy imaging showed increased cell wall buckling and fracturing with increased compression. The morphological changes led to improved enzyme diffusion and resulted in higher available surface area. The improved cellulose hydrolysis is due to changes in wood morphology as well as the removal of extractives.

Specific edge load ( SEL ) is the extensively employed theory to characterize the refining results in low consistency pulp refining. But the physical meaning of its core parameter, cutting edge length ( L C {L_{C}}), is not very clear, resulting in the limited applications of SEL in pulp refining. In this study, the physical meaning of L C {L_{C}} was investigated in two aspects, total bar sliding length per cycle and total equivalent bar length, as well as the application of two refining intensities related to it, SEL and the net tangential force per bar crossing zone ( f t net {f_{t}^{\mathrm{net}}}). After the comparison of the refining intensities and the experimental results, it was found SEL calculated by the L C {L_{C}} with physical meanings can only properly characterize the results of the pulp refining conducted by straight bar plates with constant angular parameters. While, for the situations of varied angular parameters, the f t net {f_{t}^{\mathrm{net}}} and Modified Edge Load ( MEL ), calculated by the edge length expanded empirically by Meltzer, can also better characterize the refining process, either for the evolution of fiber length or the global refining effect (pulp Schopper Riegler). In addition, the application of f t net {f_{t}^{\mathrm{net}}} can be potentially expanded to other refiner plates to gain a better understanding and optimization of the pulp refining process.

This study is focused on the development of ultrasoft facial grade tissue paper of 12.5 gsm with superior quality in terms of handfeel softness alongside enhanced productivity. To sustain in the tissue paper business, industries needs to focus in such a way that productivity should be increased with excellent product quality. Tissue industries generally loose huge productivity as well as deviation is observed in high quality low gsm facial grade tissue paper in terms of quality. This is owing to vague understanding about the creeping geometry where creep pocket angle, blade grind angle, blade MOC play a significant role to improve the productivity and produce excellent product quality. This experimental study would bridge for better understanding of impact of creping blade material and crepe blade geometry on productivity and quality of tissue paper. In this experimental study, two types of creping blade material– carbon steel and ceramic were used. Machine runability, mechanical properties of developed facial grade tissue paper was minutely analysed. It was found that while using ceramic blade, downtime reduced by 86.8 % while the production was enhanced by 10 % indicating better machine runnability with ceramic blade. Thereafter, the blade holder angle was altered to 17°, 18° and 19° along with alterations of bevel angle to 75°, 80°, 85° and 90°. All the mechanical properties of developed facial grade tissue paper was investigated and analysed. The outcome of the study indicated that by using ceramic tip creping blade with 17° blade holder angle and bevel angle at 80°, ultrasoft, high bulk facial grade tissue paper can be produced with much improved machine runnability i. e. downtown reduced by 85 % on account of blade changing frequency and production enhanced by 10 %.

This study was aimed to examine the effects of basic properties, fiber morphological properties, strength properties, wettability and optical properties on offset printing of office papers. Widely used office papers with different brands were obtained from Istanbul-Turkey. Technical characteristics of papers; basic properties, strength properties including tensile, burst, tear, and Z direction tensile strength and optical properties such as gloss, whiteness, opacity, and wettability tests were determined according to TAPPI and ISO standards. The results obtained by the tests are as follows; i) there is a great difference in water resistance between the top and the lowest values (207 %), ii) there is little difference between the highest and the lowest brightness value (3.8 %), other papers values have close to each other, iii) in the printing process there is a little difference between the highest, and the lowest gloss values (36.7 %), although the others are close iv) the highest and lowest values in CIE C* showed that it ranged from the narrowest color gamut to the widest color gamut. By applying the widely used offset printing process to commercially produced office papers, the quality levels were evaluated to raise awareness of consumers and sellers.

Paper cultural relics are important historical and cultural heritage. However, they are easy to be damaged with time. In order to improve the mechanical strength, water resistance and delay aging of paper, hydrophobically modified hydroxyethyl cellulose-methyl methacrylate copolymer emulsion for paper protection was synthesized, with hydroxyethyl cellulose as the matrix, methyl methacrylate, butyl acrylate glycidyl methacrylate, and dodecyl methacrylate as the graft polymers. The prepared emulsion was applied to paper protection. By testing the effects of emulsion with different mass concentrations on the tensile strength, folding endurance, tear strength, whiteness and gloss of paper, the suitable conditions for the application of paper protection were found. The results showed that the mechanical properties of the paper coated with 10 % emulsion were significantly improved, and the gloss and whiteness were basically unchanged. The appearance of the paper did not change obviously, which was in line with the principle of “repair as old, keep the original”. At the same time, the aging resistance and water resistance experiments show that paper coated with the new material has certain aging resistance and water resistance. Therefore, the prepared hydroxyethyl cellulose-methyl methacrylate copolymer emulsion has great application prospects in the protection of paper.

A new chitosan derivative (CS-CHO) was successfully synthesized based on chitosan (CS) and cyclohexene oxide (CHO). It proved that CHO was successfully grafted onto the amino group of CS by N-alkylation reaction through the characterization of FTIR, XRD and DSC-TGA. The mechanical properties (tensile strength, folding endurance, tearing strength), optical properties (whiteness, glossiness) of the CS-CHO coated paper sample were tested. The results showed that the mechanical properties of the paper treated with 10 % CS-CHO increased significantly without changing the appearance of the paper. The paper permanence (tensile strength, folding endurance, tearing strength and pH) of the treated paper samples tested by dry-heat aging test. The results showed that the permanence of the treated paper samples was significantly improved compared with the blank aged paper samples, which indicated that CS-CHO had the function of deacidification while reinforcing the paper samples, providing the possibility for deacidification and reinforcement in one-step method and playing a positive role in the paper preservation.

Paper cultural relics are both precious, inheritable and fragile. However, with the passage of time, paper will also be affected by a variety of factors, and will appear mildew, yellow, brittle, or even completely damaged. In order to protect the cultural relics, extend lifespan paper, CMC-acrylate-OVPOSS graft copolymerization emulsion was synthesized by using carboxymethyl cellulose (CMC) as substrate, methyl methacrylate (MMA), butyl acrylate (BA), glycidyl methacrylate (GMA), hydroxyethyl methacrylate (HEMA), octavinyl polyhedral oligomeric silsesquioxane (OVPOSS) as graft copolymer. The CMC-acrylate-OVPOSS emulsion was coated on the surface of the paper to test its protective effect on the paper. The results showed that the mass concentration of 10 % reinforcement solution coated on the paper, mechanical properties of paper were greatly improved, and the gloss and whiteness of paper were slightly changed, the paper also had a certain aging resistance and acid and alkali corrosion resistance. At the same time, the reversibility experiment showed that the reinforcement material had a certain reversibility.

As the main carrier of art and cultural heritages, paper cultural relics are suffering from aging, oxidation, acidification, bacterial corrosion and other diseases with the passage of storage time. Therefore, it is of great significance to carry out the protection of paper cultural relics. In order to improve the bacteriostatic properties, mechanical strength and delay aging of paper, sodium carboxymethyl cellulose was modified by berberine and prepare berberylated carboxymethyl cellulose (BBR-DCMC), which is mixed with KH-791 modified nano-silica and hydroxypropyl distarch phosphate to prepare a multifunctional protective liquid integrating deacidification, reinforcement and antibacterial. The paper coated with the multifunctional protective liquid showed better antibacterial and mechanical properties, and the gloss and whiteness changed slightly. The aging test and the acid and alkali resistance test showed that the paper had certain aging resistance and acid and alkali corrosion resistance. It is an ideal protective agent for paper cultural relics and has broad application prospects in paper protection.

To evaluate the changes in the ink on paper subject to accelerated degradation before and after restoration treatment, an evaluation index describing changes to ink on paper documents before and after deacidification and enhancement by combining subjective and objective evaluations was established to improve the evaluation of the effect of deacidification and enhancement agent on the restoration of paper from the perspective of the ink thereon. According to the test indicators, test and control standard boards were designed and the paper for accelerated degradation was produced. In the experiment, 0.4 mol/L sodium carbonate solution, 6wt% styrene butadiene latex (SBR latex), sodium silicate, and polyamide polyamine epichlorohydrin (PAE) compound solution was applied to the accelerated degradation paper samples, respectively. After treatment, the quality indices such as color density, color difference, handwriting contrast and handwriting line width were measured. And observers were organized to make subjective evaluation on the accelerated degradation samples before and after the treatment. The results showed that the color density of magenta ink sample decreased by 10.61 % and the edges were blurred. The contrast and line width of handwriting after the treatment were decreased slightly. After treatment with 6 wt% SBR latex, the ink density of black increased the most (by 31.62 %) with no clear change in the handwriting contrast and line width. When using sodium silicate and PAE compound solution, the comprehensive effect on the text was much better. The results of subjective evaluation were consistent with the changes of objective indices.

The objective of this study is to gain further insight into the compositional and physical changes of kraft pulp caused by oxidation with hydrogen peroxide under acidic conditions. A softwood kraft pulp has been subjected to varying degrees of oxidation. Changes in the composition, as well as resulting physical properties of laboratory sheets were investigated. Findings indicated that the oxidation resulted in an increased carbonyl group content, a decrease in intrinsic viscosity and a change in hemicellulose composition. The oxidized pulps were found to have a reduced water retention value and a slightly reduced tensile strength (4–11 % at the investigated conditions). However, a substantial increase in wet web tensile strength (6–23 %) and wet tensile strength (134–242 %) of the sheets was obtained. The sheets could easily be repulped and an increased wet strength maintained to a large extent, even after recycling of the sheets.

Eucalyptus dunnii is cultivated in Uruguay for kraft pulping purposes. However, depending on the growth site, the kraft pulping properties of the wood vary highly, and in some cases, pulping is difficult. Different batches of wood were chemically characterized and the only significant difference related to the pulping properties was the calcium content. The calcium appears to at least partly be present in the form of crystals in the lumen. Kraft pulping experiments on wood with different calcium contents indicated that high calcium led to slower delignification, and higher yield losses. Hexeneuronic acid formation was not significantly affected. Possible mechanistic explanations for these effects are discussed.

Chemithermomechanical pulp (CTMP) is often used in middle layers of multiply paperboards due to its high bulk at specified strength. Such a CTMP should consist of well-separated undamaged fibres with sufficient bonding capacity. The basic objective of this work is to examine the effect of refining on bulk, taking into account conditions such as temperature, sulphonation, refining gap and refiner size. First stage CTMP made from Norway spruce ( Picea abies ) were produced in pilot and mill scale trials. Two new parameters, Equivalent temperature related to softness and Refining gentleness are introduced that take into account refining conditions as actual temperature, softening temperature, bound sulphonate content, refining gap and refiner diameter. The results show that bulk increases linearly with refining gentleness.

In this paper, a simple method for hydrophobic modification of polyvinyl alcohol (PVA) was found. Using N-methylpyrrolidone as solvent, PVA was esterified with stearyl chloride without catalyst. The modified hydrophobic polyvinyl alcohol (MPVA) was well verified by FT-IR and XRD. Using air filter paper as receiving substrate and MPVA as spinning solution, MPVA air filter paper with water resistance and high filtration performance was prepared, and hydrophilic PVA air filter paper was prepared as controlled sample. SEM was used to observe the fiber morphology on the surface of the two composite filter papers. The contact angle of hydrophobic MPVA air filter paper (25:3) was 121.9°, and the filtration efficiency was increased to 99.9955 % and the filter initial resistance increased to 90 Pa.

The accumulation of petroleum products causes damage to ecosystems, which can be avoided with cellulose-based products. The influence of different ratios of cellulose micro/nanofibrils (MFC/NFC) on the properties of hydroxypropyl methylcellulose (HPMC) films was evaluated. Films were prepared using proportions of 0, 25, 50, 75 and 100 % (w/w) of MFC/NFC from Pinus sp. in relation to HPMC. Physical, barrier, surface, optical, morphological and mechanical properties were evaluated. Solids content, basis weight and density values increased with higher amount of MFC/NFC and thickness and porosity were reduced. SEM images showed that films with more than 50 % MFC/NFC had a more granular surface, which decreased transparency from 80 to 65 %. Water vapor penetration did not differ between films and degradation in water was reduced from 40 to 5 % with MFC/NFC addition. There were no differences in contact angle and wettability, but all films showed high resistance to fat penetration. Films with MFC/NFC content between 75 and 100 % showed higher values for tensile strength (50 to 65 MPa) and Young’s modulus (6 to 10 MPa) and lower elongation at break (1 to 2 %). The experimental results indicated that films with MFC/NFC content above 50 % have potential to be used as packaging material.

Wood is the most expensive fraction in the pulp production costs. Therefore, strategies for increasing wood quality such as faster growth, higher wood basic density and lower lignin content are drivers to pulp mills. The cultivation site as well as the eucalypt clones influence the wood quality, which, in turn, affects the pulp production performance. Thus, this work aims to evaluate the effect of the site on the wood quality for the pulp production. Three eucalypt clones from five different sites in Brazil were used in this study. These samples were selected aiming to represent a gradient of environmental stress. It was possible to observe a reduction in the content of extractives and lignin and an increase in the content of glucans in the sites with less environmental stress, reflecting in the production of pulp with less effective alkali demanded (reduction of 13.5 %) and an increase of 10.5 % in the kraft pulp screened yield. MAIP values of 22.7 ton/ha/year were obtained in the sites with less environmental stress, presenting a lower specific wood consumption. Through the production indicators, it was observed that the C1 clone is more adaptable to the regions of greater environmental stress than the other clones analyzed.

This paper presents the concept of an alkali-O 2 oxidation process for producing lignin dispersants in a feasible manner at a kraft pulp mill. The oxidation process uses O 2 gas to increase the anionic charge of lignin and the final oxidised lignin can serve as a concrete plasticiser or versatile dispersant. The integrated process provides several benefits for lignin recovery, the following lignin oxidation, and recycling of chemicals. Firstly, CO 2 precipitated kraft lignin can be used without a sulphuric acid washing step. This simplifies the lignin recovery and no excess sulphur is introduced into mill cycle. As the unwashed lignin is alkaline in nature, the need for fresh alkali in the lignin oxidation is reduced. Moreover, oxidised white liquor, readily available in the mill, can be applied as a partial source of alkali. Finally, membrane filtration of the oxidised lignin solution enables the recirculation of sodium and sulphur back to the chemical cycle and provides a concentrated lignin product. Based on a simulation study, this novel concept significantly decreased the need for purging fly ash at the mill when compared to conventional lignin recovery. It was also demonstrated that the novel lignin dispersants can compete with the tested commercial oil-based plasticisers.