The creation of a circular economy for cellulose based textile waste is supported by the development of an upcycling method for cotton polyester blended waste garments. We present a separation procedure for cotton and polyester using [DBNH] [OAc], a superbase based ionic liquid, which allows the selective dissolution of the cellulose component. After the removal of PET, the resulting solution could be employed to dry-jet wet spin textile grade cellulose fibers down to the microfiber range (0.75-2.95 dtex) with breaking tenacities (27-48 cN/tex) and elongations (7-9%) comparable to commercial Lyocell fibers made from high-purity dissolving pulp. The treatment time in [DBNH] [OAc] was found to reduce the tensile properties (<52%) and the molar mass distribution (<51%) of PET under certain processing conditions.

The successful recycling of colored textile waste and reuse of respective dyes would represent a major milestone of global efforts to reduce the environmental impact of the textile industry. The chemical upcycling of dyed pre- and postconsumer cotton waste is promoted by studying the spinability and color fastness of seven vat and reactive dyes (i.e. Indanthren Blue BC 3%, Indanthren Red FBB coll, Indanthren Brilliant Green FBB coll, Levafix Brilliant Red E-4BA, Levafix Blue E-GRN gran, Remazol Brilliant Blue R spec, and Remazol Black B 133%) during dry-jet wet spinning. Apart from the fabrics dyed with Levafix Brilliant Red E-4BA, all samples dissolved in 1,5-diazabicyclo[4.3.0]non-5-ene actetate, a superbase based ionic liquid, and could be converted to new colored man-made cellulose fibers. It was found that there is a clear discrepancy between the recyclability of dyed pre- and postconsumer cotton waste, resulting in significantly higher fiber properties up to tenacities of 59.8 cN/tex and elongations of 13.1% in case of the latter. All recycled fibers displayed a noticeable color change in the CIELab space (ΔE = 8.8–25.6) throughout the spinning process. Despite these deviations, almost all fibers and demo fabrics produced thereof exhibited bright colors that can be reused in textile industry. Only Remazol Black B 133% did not sufficiently translate to the new textile product. The wash and rubbing fastness of the fabrics knitted from the regenerated fibers was superior to the dyed waste fabrics mainly because of the homogenous distribution of the dyes along the fiber cross-section.

Purpose: While aiming to create methods for fibre recycling, the question of colours in waste textiles is also in focus; whether the colour should be kept or should be removed while recycling textile fibre. More knowledge is needed for colour management in a circular economy approach. Design/methodology/approach: The research included the use of different dye types in a cotton dyeing process, the process for decolourizing and the results. Two reactive dyes, two direct dyes and one vat dye were used in the study. Four chemical treatment sequences were used to evaluate colour removal from the dyed cotton fabrics, namely, HCE-A, HCE-P-A, HCE-Z-P-A and HCE-Y-A. Findings: The objective was to evaluate how different chemical refining sequences remove colour from direct, reactive and vat dyed cotton fabrics, and how they influence the specific cellulose properties. Dyeing methods and the used refining sequences influence the degree of colour removal. The highest achieved final brightness of refined cotton materials were between 71 and 91 per cent ISO brightness, depending on the dyeing method used. Research limitations/implications: Only cotton fibre and three different colour types were tested. Practical implications: With cotton waste, it appears to be easier to remove the colour than to retain it, especially if the textile contains polyester residues, which are desired to be removed in the textile refining stage. Originality/value: Colour management in the CE context is an important new track to study in the context of the increasing amount of textile waste used as a raw material.

Recycling of textiles is of importance due to the large amount of waste generated from the increasing consumption and use worldwide. Cotton-rich pre-consumer textiles are considered as potential raw material for production of man-made regenerated fibres, but demands purification from the blends with synthetic fibres as well as the dyes and finishing chemicals. In this study we explore the use of different pre-treatments of pre-consumer textiles to meet specific parameters for production of fibres in the cold NaOH(aq) or cellulose carbamate process. The pre-treatments consisted of different bleaching sequences and were performed on both uncoloured and coloured pre-consumer textiles. For the uncoloured textile, degree of polymerisation and amount of inorganic content was efficiently reduced making the material suitable for both the cold NaOH(aq) and the cellulose carbamate process. In case of the coloured textile, the pre-treatments were able to remove the dye and decrease the inorganic content as well as reduce the degree of polymerisation but only sufficiently enough for production of fibres in the cellulose carbamate process. The work was able to prove a fibre-to-fibre concept while further optimisation of the regeneration steps is expected to improve the mechanical properties of the produced fibres in future studies.

Article Determination of phenomena involved in impregnation of softwood chips. Part 2: Alkali uptake, alkali consumption and impregnation yield was published on August 1, 2012 in the journal Nordic Pulp & Paper Research Journal (volume 27, issue 3).

Spruce bark residues obtained after alkaline extraction of polyphenols were studied as raw material for pulping and making of pulp sheets. Kraft pulping of mixtures containing wood chips and 5 % or 20 % wt. bark residues produced unbleached pulps with higher screened yields and lower kappa number than wood pulps. During bleaching, the evolution of brightness along with kappa reduction followed a similar trend in all pulps, and bleached mixed pulps with ISO brightness >89 % could be obtained with somewhat lower intrinsic viscosity than wood pulps. The high content of calcium and other metal elements in spruce bark, which was partially reduced by the alkaline extraction, did not seem to impair the pulping and bleaching of the pulps. Sheets made from mixed pulps had rather similar optical and mechanical properties than sheets from wood pulps, and interestingly, sheets produced from mixed pulps with 20 % bark residues showed higher bulk as a function of internal bond strength, which may be exploited in packaging boards. Pulping of bark residues to produce mixed pulps would thus maximize the utilization of spruce bark streams after extracting the polyphenols, while increasing the pulp output in the mills.