Field of the invention and background

The present disclosure describes the manufacturing of regenerated cellulosic fibers from recycled cellulose material such as waste paper, recycled cotton and viscose textile material. The manufacturing process involves pre-treatment of the cellulose feedstock in order to purify the cellulose material prior to dissolving the substantially pure cellulose in sodium hydroxide thereby forming a spin dope. The textile fiber manufacturing process further comprises regenerating new cellulose fibers in an alkaline coagulation bath followed by washing, stretching, and drying of the produced fibers. Sodium hydroxide solvent is recovered and recycled to the dissolving step for dissolving substantially pure cellulose.

Regenerated cellulosic fibers herein are defined as cellulosic fibers comprising more than 85 % by weight of cellulose. Cellulose is derived from D-glucose units, which condense through (l->4)-glycosidic bonds. This linkage motif contrasts with that for a (I- >4)-glycosidic bonds present in starch, glycogen, and other carbohydrates. Cellulose is a straight chain polymer: unlike starch, no coiling or branching occurs, and the molecule adopts an extended and rather stiff rod-like conformation, aided by the equatorial conformation of the glucose residues. The multiple hydroxyl groups on the glucose from one chain form hydrogen bonds with oxygen atoms on the same or on a neighbor chain. Hydrophobic interactions combined with hydrogen bonds hold the chains firmly together side-by-side and forming micro fibrils with high tensile strength. This confers to tensile strength in cell walls, where cellulose micro fibrils are meshed into a polysaccharide matrix.

Celluloses are well known and are described, for example, in Encyclopedia of Polymer Science and Technology, 2nd edition, 1987. Celluloses are natural carbohydrate high polymers (polysaccharides) consisting of anhydroglucose units joined by an oxygen linkage to form long molecular chains that are essentially linear. Cellulose can be hydrolyzed to form glucose. The degree of polymerization (DP) ranges from 1000 for wood pulp to 3500 for cotton fiber, giving a molecular weight of from 160,000 to 560,000. Cellulose can be extracted from several types of vegetable tissues (wood, grass, and cotton).

Many properties of cellulose depend on its chain length or degree of polymerization (DP), the number of glucose units that make up one polymer molecule. Cellulose from wood pulp has typical chain lengths between 300 and 1700 units; cotton and other plant fibers as well as bacterial cellulose have chain lengths ranging from 800 to 10,000 units. Plant-derived cellulose is usually found in a mixture with hemicellulose, lignin, pectin and other substances, while bacterial cellulose is quite pure, has a much higher water content and higher tensile strength due to higher chain lengths.

Cellulose is a natural compound with use in paper and textile products. Cotton is a cellulosic material used primarily in textile applications. In spite of increased recycling, large amounts of waste paper and waste textile material is generated, and it is desirable to establish methods and processes for conversion of waste cellulose into new consumer products such as textile fibers. The disclosure is directed to an efficient and environmentally superior process for manufacturing of textile fibers from cellulosic waste and residue streams. Cellulosic waste material may comprise mechanical pulp, recycled paper, waste paper, recycled cellulosic textiles including cotton and viscose fibers, recycled carton board, and mixtures of such wastes. Such waste materials are optionally deinked before subjected to further processing by any of pre-treatment steps.

Methods for the manufacturing of a dissolving pulp from recycled cotton is known from e.g. the disclosure of EP3339504A1 where such dissolving pulp is used for producing regenerated cellulose molded bodies and lyocell or viscose fibers.

Moreover, in W02G13124285A1 a method is disclosed for regeneration of a cellulose containing material comprising several sequential steps. The final product can be a viscose fiber. Summary of the invention

The present invention is directed to a process for the production of regenerated cellulosic fibers from a cellulosic spin dope, said process comprising the steps of:

a) treating a recycled cellulosic waste material to remove at least one of lignin, hemicelluloses, and contaminants from the recycled cellulosic waste material thereby providing a purified cellulosic intermediate product,

b) dissolving the purified cellulosic intermediate product in an alkaline liquor to form a cellulosic spin dope,

c) injecting the cellulosic spin dope into a coagulation bath to form a tow, d) washing and stretching the tow under alkaline conditions and/or acidic conditions,

e) cutting the tow to form regenerated cellulosic fibers.

In relation to the above it should be mentioned that step d) may be performed in alkaline conditions or acidic conditions, or in fact in both, that is where at least one step is performed in an alkaline condition and at least one step is performed in an acidic condition.

Some other embodiments of the present invention and details thereof are presented below.

Pre-treatment

In the present disclosure, the cellulosic waste material is described as feed cellulose material (or just‘feedstock’). The feed cellulose material used for manufacturing of new high-quality fibers needs to be pre-treated prior to being dissolved in a suitable cellulose solvent. Such pre-treatment of the feed cellulose material may consist of treatment in several stages to remove ash, lignin and/or hemicellulose. The pre-treatment yields substantially pure alfa cellulose, preferably cellulose having an alfa cellulose content exceeding 85 % by weight of dry cellulose. The pre-treatment more preferably yields alfa cellulose content over 90 % by weight of dry cellulose. Pre-treatment procedures are further described below. In order to obtain a cellulose dissolvable in sodium hydroxide solvent, the molecular weight of cellulose may be reduced to the desirable range by at least one of: chlorine dioxide, oxidation with oxygen and/or strong oxidants such as ozone or hydrogen peroxide under alkaline or acidic conditions, enzymatic treatment, hydrolysis (acid or alkaline catalyzed), physical/mechanical degradation (e.g., via the thermomechanical energy input of the processing equipment) such as for example steam explosion treatment, or combinations thereof. For example, an oxidant alone or together with a metal such as iron or manganese may be introduced into an alkaline oxygen

delignification stage to achieve the desired level of depolymerization of the cellulose. A chloride dioxide stage may be operated at harsher acidic conditions. The cellulose feed material may be purified and hydrolyzed to the desired DP level by treatment with acids such as sulfuric acid, washing the pulp, and thereafter dissolving the pulp in the solvent. The exact chemical nature of the cellulose and molecular weight reduction method is not critical as long as the average molecular weight is in an acceptable range (i.e. with a degree of polymerization (DP) in a suitable range (further described below)).

For certain feedstocks, ash needs to be removed from the feedstock prior to dissolving the feedstock in the sodium hydroxide solvent. For other feedstocks, hemicellulose and/or lignin content may have to be lowered which can be done by methods well known in the art and further specified in figure and claims. In an embodiment where the cellulosic waste material has a lignin content of up to 20 % by weight, the cellulosic waste material is subjected to chemical delignification with an alkaline cooking chemical, such as sodium hydroxide, for reducing the lignin content to less than 10 % by weight, or preferably less than 5 % by weight. This provides cellulosic material with lower lignin content. The delignification process may be carried out using at least one of kraft pulping, soda pulping, or oxygen delignification.

Although not required, substituted cellulose can be used in part or in all of the cellulose used for manufacturing a cellulosic spin dope. When substituted cellulose is desired for increased solubility of cellulose in a sodium hydroxide solvent, chemical modifications of cellulose typically include one or more of carbamatization, etherification and esterification. Substitution or derivatization of cellulose may be performed in any step prior to dissolution in the cellulose solvent forming the spin dope.

From the viewpoint of further reducing the manufacturing cost for producing the cellulosic fiber, it is preferred that the cellulose content of the cellulose dope is above about 5 % by weight of the spin dope, while keeping the dissolution ratio of the cellulose in the alkaline solvent at 99.0% by weight or more. To achieve this, the hydroxyl groups of the cellulose in the cellulose slurry may be partially modified by reaction with a reagent which is reactive with a hydroxyl group in the presence of an alkali

(derivatization). Examples of such reagents include carbamate, a vinyl compound, and an etherification agent. When such a reagent is not used, the cellulose content of the cellulose dope is usually in the range of from 5 to 7% by weight. On the other hand, by employing the above-mentioned modification of the hydroxyl groups of the cellulose, the cellulose content of the cellulose dope can usually be increased to the range of from 7 to 12% by weight.

Additives such as Zn compounds and/or urea may be present in the spin dope in order to prevent undesired gelling. The spin dope composition comprises from about 5 to about 12 %, preferably from about 5 to about 9 % of cellulose or derivatized cellulose.

An example of a spin dope preparation and textile fiber spinning process is described in European patent publication EP3231899.

In order to further describe the scope of the present disclosure, it is referred to appended fig 1 and the claims.

In one embodiment of the present disclosure, the coagulation and fiber washing is performed under alkaline conditions. This enables the recovery and recycling of solvent sodium hydroxide. It has been shown that coagulation and fiber regeneration is a rather slow process and that it is advantageous to wash the nascent fibers in the form of a tow and to stretch the tow or filaments prior to cutting. Optionally the alkaline washing and/or stretching stages can be followed by acidic wash stages prior to cutting.

In one embodiment of the present disclosure, additives such as sodium sulfate or carbonates are present in the coagulation bath to increase ionic strength of the coagulation liquid and to promote deswelling and transport of solvent out from the nascent cellulosic fiber filaments or fiber tow.

Embodiments of the invention

Below some specific embodiment of the present invention are disclosed and discussed further.

The present invention is directed to recycling, recovering and thus recovery of

chemicals. In line with this, according to one embodiment of the present invention, at least one chemical used in step c) and/ or d) is recovered and recycled to step b).

According to yet another embodiment of the present invention, the recycled cellulosic waste material is obtained from waste paper, recycled cotton and/or a viscose textile material or a combination thereof. According to one preferred embodiment of the present invention, the recycled cellulosic waste material is obtained from a viscose textile material. Therefore, according to one embodiment the recycled cellulosic waste material comprises viscose. Moreover, according to yet another embodiment of special interest, the recycled cellulosic waste material comprises at least 50 wt%, preferably at least 70 wt% viscose material.

Any cotton or polyester fibers present in the feedstock may be, at least partially separated prior to dissolution of the treated fibers in the solvent. In relation to the expression“a viscose textile material” it should be noted that this implies a material comprising viscose, e.g. at least 50% or more, such as up to a very high proportion of viscose. Moreover, and based on the above, according to one embodiment of the present invention, the purified cellulosic intermediate product charged to step b) predominantly originates from viscose fibers textile material. Furthermore, according to one embodiment, the recycled cellulosic waste material has been pre-treated by removal of button(s) and/or zipper(s).

Referring to step c), according to one specific embodiment of the present invention, step c) comprises injecting the cellulosic spin dope into a film forming device to form cellulosic films. Moreover, according to yet another embodiment, step c) comprises injecting the cellulosic spin dope through nozzles forming a nonwoven cellulosic product.

Furthermore, according to yet another embodiment of the present invention, the purified cellulosic intermediate product has at least one of: a brightness exceeding SIS 88, a lignin content below about 10 %, and a degree of polymerization (DP) in the range of 150-500, preferably having a lignin content below about 10 %.

According to one embodiment of the present invention, the purified cellulosic

intermediate product has a degree of polymerization (DP) in the range of 150-500, preferably in the range of 185 - 325.

In relation to the above it should be noted that the molecular weight of a cellulose substrate may be determined by using intrinsic viscosity (IV). This may e.g. be

performed by using a standard method, such as IS05351 :2010. When a value of the intrinsic viscosity is set, this may be used to calculate a value of the degree of

polymerization (DP), for instance via DP=0.7277 ^* (IV) ^A 1.105. For instance, a DP value in the range of 185 - 325 then corresponds to a value of the intrinsic viscosity (IV) of about 150 - 250 mL/g.

Based on the above explanation, according to one embodiment of the present invention, the purified cellulosic intermediate product has an intrinsic viscosity (IV) of between 100 - 700 mL/g, preferably 150 - 400 mL/g, more preferably 150 - 250 mL/g. Furthermore, according to yet another embodiment of the present invention, the IV value in the purified cellulosic intermediate product is in the range of 190 - 220, such as 200 - 210, after adaptation.

Moreover, several steps according to the present invention may be performed in different conditions. According to one embodiment, step c) is performed in an alkaline coagulation bath. According to another embodiment, also step d) is performed under alkaline conditions.

In relation to the above it should be noted that the present invention also embodies using an acidic bath in step c) and/or d), either in both these steps or in any of them.

This is further described below, especially in relation to the embodiment when electrolysis is applied for the recovery of sodium hydroxide in step b) and further. If a fully acidic condition is applied, then it is preferred to also use electrolysis to recover the alkaline substance(s), such as sodium hydroxide.

According to the present invention, several different types of technologies may be used for different steps, e.g. in step a). According to one embodiment, the treating of step a) comprises at least one of:

o Alkaline extraction

o Steam explosion treatment (STEX) with or without sulphur dioxide addition o Acidic wash

o Enzymatic treatment

o Bleaching by chlorine dioxide, hydrogen peroxide, ozone or hypochlorite o Electron beam treatment

o Oxygen treatment under alkaline conditions

In relation to the above it should be said that bleaching and/or oxygen treatment under alkaline conditions are preferred, but also for instance STEX is a very valid alternative to use. Furthermore, according to yet another embodiment the treating of step a) comprises alkaline extraction and/or steam explosion treatment (STEX) with or without sulphur dioxide addition, preferably at least alkaline extraction. Furthermore, the alkaline extraction may be performed with sodium hydroxide and optional additives including sodium sulfide, glycerol and ethanol. Moreover, a STEX pre-treatment may be performed by the addition of ethanol or sulphur dioxide. To give another possible example, an acidic wash is performed with sulfuric acid. Furthermore, a bleaching is suitably carried out with oxidative chemicals selected from the group of peroxides and peracids, chlorine dioxide, hypochlorite and ozone and combinations thereof, and optionally said bleached pulp is subjected to alkaline extraction, in order to reduce the lignin content of the fibers.

According to yet another embodiment of the present invention, step a) further comprises reacting the purified cellulosic intermediate product with urea such that the purified cellulosic intermediate product is a purified cellulose carbamate intermediate product.

Moreover, and as hinted above, the alkaline liquor of step b) suitably comprises sodium hydroxide. Furthermore, according to another embodiment the alkaline liquor of step b) comprises optional additives such as zinc compounds or urea.

As discussed above, sodium hydroxide is a preferred solvent for dissolving cellulose to form a spin dope according to the present invention. In line with this, according to one embodiment, at least one chemical used in step c) and/ or d) and being recovered and recycled to step b) is at least sodium hydroxide. Moreover, according to yet another embodiment, sodium hydroxide is recovered by means of evaporation or electrolysis. Either of evaporation or electrolysis is fully possible, and the alternatives may be preferred depending on other conditions. As hinted above, when using an acidic bath, then electrolysis is preferred.

According to one embodiment, the cellulosic spin dope formed in step b) comprises between 5% to 12 % cellulose based on the total weight of the cellulosic spin dope. Moreover, according to another embodiment, the sodium hydroxide concentration in the spin dope is in the range of 5-10 wt%. Furthermore, as disclosed above, the spin dope may comprise Zn compounds or urea.

According to yet another embodiment, the purified cellulosic intermediate product prior to dissolving in step b) comprises below 1 wt% lignin, Moreover, the purified cellulosic intermediate product may be subjected to an acid treatment to remove ash before step b).

Furthermore, according to yet another specific embodiment of the present invention, the purified cellulosic intermediate product prior to dissolving in step b) exhibits at least one of the following properties:

- a lignin content of less than 0.7 wt%, in particular a lignin content of 0.3 to 0.6 wt%;

- a Fock value of 55 % or higher;

- alfa cellulose content of 90 wt% or more

- a R18 % value of 88% or higher;

- hemicellulose content of from 0.1 up to 10 wt%; and

- an intrinsic viscosity of 150 - 400 mL/g.

The present invention is also directed to spun fibers produced by the process according to the present invention, where the spun fibers have a titer in the range of 0.5 to 3 dtex, preferably 0.8 to 1.5 dtex. Moreover, the spun fibers suitably have conditioned dry tenacities > 18 cN/tex, preferably > 25 cN/tex.

Furthermore, the present invention also provides use of spun fibers produced by the process according to the present invention, for the preparation of a textile fiber product. Moreover, the present invention is also directed to the use of spun fibers produced by the process according to the present invention, for the preparation of nonwovens. Description of the figure and related material

In Fig 1 , cellulosic feedstock (1 ) is charged to one or more pre-treatment steps (2) in order to produce substantially pure dissolving grade cellulose. The substantially pure dissolving grade cellulose is then charged into cellulose dissolving step (3). A sodium hydroxide solution (9), recycled from the chemicals recycling plant (13), is also charged into the cellulose dissolving step (3). Make up sodium hydroxide (and optional other additives such as ZnO) (7) is charged to cellulose dissolving step (3) as needed to balance any losses of sodium compounds in the overall process. Cellulose spin dope discharged from the cellulose dissolving step (3) is charged trough filtration and deaeration units (not shown) into the spinning/fiber regeneration plant (4) comprising spinnerets for injection of spin dope into an alkaline coagulation bath. Regenerated cellulosic fibers are washed/stretched/dried/cut in several process steps represented by units in block (5) in Figure 1. A cellulosic staple fiber product suitable for the

manufacturing of textile products is exported from the overall plant (6). Fresh wash liquid (water) is charged to washing steps in (5) through line (12) and spent chemicals from spinning plant (4 and 5) is discharged through line (1 1 ) and charged to the chemicals recycling plant (13). Any salts used to support coagulation and fiber formation in (4) is recovered from the spent spinning liquid and charged to unit (4) through line (10). Wash liquids and sludges (8) are discharged from cellulose feed pre-treatment steps (2) optionally combined with bleed off streams (14) from the chemicals recycling plant (14). Such streams (8 and/or 14) can advantageously, after concentration, be charged to a chemicals recovery boiler in a kraft or sulphite pulp mill. Alternatively, after removal of metals such as Zn, they can, alone or combined, be charged to a sewer or bio sludge treatment plant.

Proof of concept experiment

Two different viscose type materials have been dissolved in cold alkali conditions (7 % NaOFI at -5°C , intense mixing): viscose filaments from a filament bobbin and a recycled white garment made from 95% viscose and 5% elastan. The viscose filament had an intrinsic viscosity of 162 ml/g. The filament was cut in shorter pieces, approximately 5 mm, and was swollen in water before the dissolution, while the garment was cut in small squares approximately 10 ^* 10 mm.

In both dissolutions, some un-dissolved material occurred. In the filament case, some gel clumps were present, while in the garment case, the elastan fibres were un dissolved. Before filterability tests, these large particles were removed by a course filtration.

Kr (clogging) value (measured according to viscose standard method) for the filament was 1607, while for the garment the value became 1570. Cellulose content in the filament dope was measured to 6.1 %, while for the garment the cellulose concentration was 5.53%.

The high Kr values was caused by un-dissolved fibres. In the filament dope, small filaments were visible, probably due to un-optimized dissolving process. In the garment dope, clearly visible fibres in other colours were seen (cotton and/or polyester fibres) The undissolved material was separated by fine filtering and a good spindope for the manufacturing of cold alkali textile fibre was obtained.

Dissolution of adapted pulp and a viscose garment in cold alkali and consecutive spinning

To compare cold alkali dissolution and spinning of adapted dissolving pulp and recycled viscose garment, a test was performed. The samples were dissolved with 6% cellulose, 7.5% NaOH and 0.95% ZnO concentration at -5°C. The dissolution was performed in a cooled vessel with vigorous stirring in 15-30 min.

Both components were easily dissolved during dissolution. The adapted pulp dope contained 5.97% cellulose while the viscose garment dope contained 5.78%. Clogging value, K _r for the adapted pulp was 1236, while for the garment the Kr-value was 1570. Both dopes were filtered before spinning, the adapted pulp with a 30 pm filter while the viscose garment was initially filtered with a 100 pm filter, then 30 miti. The reason for a double filtration of the viscose was that it contained both small amount of elastan synthetic fibres, but also other fibres collected during wearing. This could also cause the high Kr-value.

Spinning was done on a small spinning pilot at ambient temperature and the spin-bath composition was 130 g/l H2SO4, 310 g/l Na2SC>4 and 9.5 g/l ZnSC>4. There were no major differences in behavior between the two dopes in the spinning, however, lower stretching was needed to be applied compared to standard viscose spinning due to filament strength.