Patent Application
20230090830
The present invention relates to a swellable polymer fibre incorporating an antimicrobial and a method of producing the same and in a particular, although not exclusively, to a spun or extruded swellable polymer fibre incorporating an antimicrobial agent for use as a wound dressing.
A variety of different dressings have been developed for treating many different types of wounds from grazes and cuts to more serious and problematic wounds such as burns or ulcers. In particular, these latter types of wound tend to produce significant quantities of exudate which more conventional pads and bandages cannot absorb.
Wound dressings may be formed from gauzes, films, woven or non-woven fabrics and swellable materials including hydrocolloids, alginates, hydrogels, polysaccharides. Such wound dressings may be natural or synthetic and are designed specifically for their biocompatibility.
For major wounds such as burns or ulcers it can be advantageous to prevent infection by introducing an antimicrobial agent to the wound. This may be applied directly before a fresh dressing is applied or more recently the antimicrobial may be incorporated into the dressing which is then placed directly onto the wound. The therapeutic and antimicrobial properties of iodine have been known for centuries with iodine-rich plants being used in the preparation of topical pastes to reduce pain and to help with wound healing. Iodophors are complexes of iodine and a solubilizing agent or carrier. The carrier also functions to control dissociation of the iodine to provide a sustained release when incorporated in a wound dressing and present on a wound in contact with wound exudate. A particular iodophor that has found more recent medical application is povidone-iodine (PVP-I) which is a complex salt of polyvinylpyrrolidone with triiodide ions. The antimicrobial activity of an iodophor, present within a wound dressing, is dependent on the amount of ‘free’ iodine, alternatively-termed ‘available’ iodine that can be released into or onto the wound. This available iodine may be identified quantitatively via iodometry.
WO 2013/140362 A1 discloses a polymeric composite material having antimicrobial and biodegradable properties. The material is used to form medical devices having antiseptic action that is formed from a matrix of alginate and PVP-I. The composite material is used for producing films, micro-capsules and suture threads from which iodine may be released.
EP 0532275 B1 describes a wound dressing having an anhydrous water-soluble gel formed from a polysaccharide or cellulosic polymer together with a humectant. The dressing may also comprise a medicament or additive such as chlorohexidine, a silver compound or an antimicrobial such as PVP-I.
US 2011/0171284 A2 describes a medical dressing for wound healing including a sucrose, PVP-I and a gelling agent sufficient to thicken the composition to control release of sucrose and iodine to the wound.
WO 2013/078998 A1 describes a slow-release ophthalmic composition containing PVP-I to treat acute ophthalmic infections. The composition includes a pharmaceutically acceptable excipient (e.g. water) and PVP-I formed in microspheres with sodium alginate,
However, iodine-based antimicrobial wound dressings are required offering enhanced exudate management and sustained and controlled release of the pharmaceutically active agent.
It is an objective of the present invention to provide a pharmaceutically active fibre, filament or yarn to form a material suitable as a wound dressing exhibiting moisture absorbing characteristics whilst providing a sustained and controlled release of the antimicrobial agent. It is a further objective to provide a fibre and/or a non-woven felt like material having the desired physical and mechanical characteristics for the treatment of a variety of different types of wound from minor cuts and grazes to more serious forms such as burns and ulcers.
The objectives are achieved by providing a fibre, yarn, multi filament and/or material exhibiting enhanced moisture absorbing qualities together with a controlled and sustained release of iodine (as an antimicrobial agent). In particular, the present fibre and material when positioned at a wound are effective to achieve a desired moisture vapour transmission rate from the wound and through the material, a desired physical integrity so as not to degrade when absorbing moisture and exudate, moisture retention so as to provide a hygroscopic humectant whilst also enabling convenient release or decoupling from the wound when required.
According to a first aspect of the present invention there is provided a swellable fibre formed by a method of extrusion of a primary polymer comprising the steps of creating an aqueous dope solution containing a primary polymer and povidone-iodine; spinning or extruding the dope solution into a coagulation bath via a spinneret having a plurality of holes to form an extruded multi filament fibre; and drawing the fibre from the coagulation bath.
The present materials and processes are designed specifically to provide moisture absorbing, antimicrobial structures having a desired moisture vapour transmission rate (MVTR), physical integrity—so as not to degrade when exposed to exudate and in a moisture absorbed swollen configuration in addition to providing controlled and sustained antimicrobial release at the wound
The present materials and methods may utilise a variety of different primary polymers including water-soluble polymers being natural and/or synthetic materials. Such primary polymers are moisture absorbing swellable polymers and include for example any one or a combination of a polysaccharide; a polysaccharide based material; or a hydrocolloid forming material.
Optionally, the primary polymer comprises any one or a combination of an alginate, chitosan, chitin, pectin, carboxymethyl cellulose, -hydroxypropyyl methylcellulose, gellan, psyllium or konjac.
Optionally, the primary polymer is a high guluronic acid (G) or high mannuronic acid (M) acid content alginate, optionally having a molecular weight in the range 32,000 and 400,000 g/mol.
Optionally, a concentration of the povidone-iodine in the fibre is in a range 0.5 to 40 wt %, 0.5 to 30 wt %, 0.5 to 25 wt % or 1.0 to 20 wt % or 0.5 to 20 wt % based on a total weight of the fibre/material.
According to a further aspect of the present invention there is provided a swellable fibre comprising an elongate multi filament body formed from a plurality of intertwined filaments, each filament comprising a primary polymer and povidone-iodine incorporated within the respective filament.
Optionally, the primary polymer comprises a high G-alginate or a high-M-alginate and a povidone-iodine concentration in the range 0.5 to 20 wt % based on a total wt % of the fibre.
Optionally, the primary polymer swellable fibre comprises psyllium.
Preferably, the present fibre and methods utilise additional compounds to further control the release of iodine from the fibre. Such additional components may include secondary water-soluble control compounds such as a water-soluble control compound that comprises a polyether, an alkyl ether, a compound having a C—O—C linkage, a polyol, a glycol or any one or a combination of polyethylene glycol and-propylene glycol. In particular, it is preferred that the water-soluble control compound is polar or at least partially polar. It is hypothesised that the water-soluble control compound may interact via electrostatics and/or structural conformation so as to at least partially inhibit disassociation of the iodine from the PVP complex. Accordingly, the iodine is inhibited from uncontrolled or free release from the material by interaction of the iodine and/or the iodine complex with the water-soluble control compound.
Preferably, the water-soluble control compound comprises propylene glycol and/or polyethylene glycol, wherein a concentration of the water-soluble control compound is such so as to provide the desired sustained release of iodine from the material when exposed to moisture/exudate at the wound. Such a concentration within the final material (suitable for use as a wound dressing) may be in the range 0.5 to 40 wt %, 0.5 to 30 wt %, 0.5 to 25 wt % or 1.0 to 20 wt % based on a total weight of the material.
Optionally, the povidone-iodine is present internally within the multi filament fibre at or towards a core of each filament of the multi filament fibre and at an external surface of the multi filament fibre.
According to a further aspect of the present invention there is provided a method of forming a swellable polymer based fibre comprising: creating an aqueous dope solution containing a primary polymer and povidone-iodine; spinning or extruding the dope solution into a coagulation bath via a spinneret having a plurality of holes to form an extruded multi filament fibre; and drawing the fibre from the coagulation bath.
Optionally, the dope solution may comprise a water-soluble control compound comprising a polyether, an alkyl ether, a compound having a C—O—C linkage, a polyol, a glycol or any one or a combination of polyethylene glycol and propylene glycol.
Optionally, the coagulation bath comprises an aqueous solution containing calcium chloride and any one or a combination of polyethylene glycol, propylene glycol or isopropanol.
Optionally, the coagulation bath further comprises povidone-iodine.
Optionally, the step of drawing the fibre from the coagulation bath comprises passing the fibre into at least one washing bath containing a washing liquid. Optionally, the washing liquid may comprise acetone and/or isopropanol. Optionally, the washing liquid may further comprise any one or a combination of polyethylene glycol, propylene glycol, a finishing agent, water and/or povidone-iodine.
Optionally, the method may comprise passing the extruded fibre into a plurality of washing baths in-series. Optionally, at least some of the washing baths have different washing liquids with different respective constituents.
Preferably, the PVP-I dope, coagulation bath and/or washing bath(s) further comprises a polar organic solvent. The polar organic solvent is advantageous as a substitute to reduce the amount of water in the respective aqueous solution. This has been found to facilitate drying of the processed material to remove excess liquid. Incorporating a polar organic solvent within the solution with which the present material is contacted, is further beneficial to increase the softness of the final material. Such a property is advantageous for use as a wound dressing as will be appreciated. Optionally, the polar organic solvent comprises any one or a combination of an aldehyde, a ketone, an alcohol, an acetal or a compound with a hydroxyl group or a carbonyl group. More preferably, the polar organic solvent may comprise acetone and/or isopropanol.
Importantly, the present PVP-I fibre, once manufactured, comprises a desired moisture content. This avoids the resultant fibres agglomerating which is particularly important for the multi filament processing. Additionally, it is important to provide a resultant material that comprises a generally uniform structure devoid of cracks or undesired large internal cavities or voids otherwise associated with poorly spun fibres A PVP-I fibre having a desired moisture content would facilitate crimping, opening, carding and conversion into wound dressing with the desired physical and mechanical characteristics such as the desired moisture vapour transmission rate, exudate absorption etc. Optionally, the present PVP-I fibre comprises a moisture or liquid content in the range 5 to 60%, 10 to 60%, 15 to 55%, 20 to 50%, 25 to 50%, 30 to 50%, 30 to 45% or 35 to 40% moisture. The moisture content may be determined by any suitable method. For example, the moisture content may be determined by subtracting the dry weight of the fibre from the appropriately moistened fibre and then dividing this difference (moisture content) by the total weight of fully moistened fibre. The values of moisture content reported herein therefore are relative moisture wt % ranges of the amount of liquid within the moistened fibre on the processing line.
The present PVP-I fibre may comprise a moistening liquid being any one or a combination of water, a water-based solution, an organic liquid, an organic solution, acetone, isopropanol.
Optionally, the present fibre and/or material may comprise at least one additional or further antimicrobial agent. The further antimicrobial agent may comprise silver, a silver ion or a silver containing compound. Optionally, the further antimicrobial agent comprises a metal species being one or a combination of the set of Zn, Cu, Ti, Pt, Pd, Bi, Sn, Sb.
Preferably, the method further comprises cutting the PVP-I fibres and compressing, squeezing or pressing the moistened fibre to expel excess moisture prior to opening, carding and before allowing the fibre to dry.
Optionally, fibres produced may be processed in dry form and more preferably are processed in damp form with the fibre retaining 30-45% moisture.
According to a further aspect of the present invention there is provided a non-woven felt-like material comprising a swellable fibre as claimed herein. Optionally, the material is a wound dressing material.
According to a further aspect of the present invention there is provided a material comprising a swellable fibre as described and claimed herein, the material being any one of: a wound dressing material; a nasal packing material; a dental packing material; a suture; a seton. Optionally the present material when used as a wound dressing or packing material is non-woven. Optionally the present material when used as a suture or a seton is fibrous.
A specific implementation of the present subject matter will now be described, by way of example only, and with reference to the accompanying drawings in which:
The present antimicrobial swellable fibre is suitable for the manufacture of a non-woven felt-like material that, in turn, may be utilised as a wound dressing for the treatment of a variety of different types of wound from cuts and grazes to more serious burns, ulcers and the like where exudate management is critical. The present fibre is conveniently formed from a multifilament via an extrusion or spinning process in which the fibre is spun or extruded from an aqueous dope solution into a coagulation solution. The present materials and processes provide spinning, extruding conditions and processing parameters to produce highly swellable fibres incorporating ‘available’ iodine within the fibre core and at the fibre surface. The iodine is in a form of an iodine complex and included at a concentration level sufficient to provide antimicrobial activity. Such concentration levels may be of the order of greater than 1 wt % ‘free’ iodine within a total weight of fibre. The present materials and processes are specifically designed to provide a material having a desired moisture vapour transmission rate (MVTR), physical integrity—so as not to degrade when exposed to exudate and in a moisture absorbed swollen configuration, in addition to providing controlled and sustained antimicrobial release at the wound.
The present materials and methods may utilise a variety of different primary polymers including natural or synthetic materials. Such primary polymers are moisture absorbing swellable polymers and include for example polysaccharides or polysaccharide based materials, hydrocolloids, biopolymers. A preferred form of primary polymer is a polysaccharide alginate.
The present fibre and methods may utilise additional compounds to further control the release of iodine from the fibre. Such additional components may include secondary water-soluble control compounds such as polyethers, alkyl ethers, a glycol such as propylene glycol or a compound having a C—O—C linkage such as or polyethylene glycol (PEG).
Referring to
The partially dried fibres 112 are then passed into a first wash bath 113 via advancing rollers 111. Subsequently, the fibres 112 are passed into successive baths 114, 115, 116 and 117. Such baths may contain the same or different washing solutions including combinations of water, alcohols, organic solvents and further finishing compounds. At a stage between baths 115 and 116, the fibres 112 are squeezed again by mangling rollers 119 for further moisture removal. The washed fibres 121 are then passed into a final bath 118 and/or winding unit for collection and onward dispatch.
The spinning line further comprises extraction systems 120 to remove moisture and solution vapour from coagulant bath 106 and washing baths 113 to 118.
As will be appreciated, the example spinning line for the manufacture of swellable fibres in accordance with the present disclosure may comprise additions or variations to the components described and illustrated referring to Example 1. Additionally, spinneret head 105 comprises a plate having a plurality of holes, apertures or capillaries through which the dope solution is passed to form the coagulated tow. A multi-hole spinneret accordingly provides resulting multifilaments being a collection of monofilaments associated, spun and/or entrained together to form a collective fibre assembly. As will be appreciated, such a multifilament fibre may then be processed by subsequent downstream operations to create a non-woven fibrous material suitable for use as a wound dressing or the like.
The following examples are based on an alginate fibre incorporating polyvinyl pyrrolidone (PVP-I). However, as indicated, the present material and method may equally comprise other swellable polymers and variations of spinning or extrusion processes.
In this example, the preparation and effect of solid content on the viscosity of PVP solution alone or with sodium alginate was investigated in addition to the effects on the spinnability and fibre properties with the addition of PVP-I to alginate solutions.
Aqueous solutions of 2, 10 and 20% w/w PVP solutions were easily prepared by mixing 5 g, 25 g and 50 g of PVP powder (lot SLBV2087, m.pt 150-180° C. supplied by Sigma-Aldrich) into 245 g, 225 g and 200 g of water respectively. After deaeration, the viscosity of each solution at 25° C. was determined using a Brookfield digital viscometer (RVTD) and RV spindle size 04. The pH of the solutions appeared to change from 6 for the 2% w/w solution to about 4 for the 20% w/w solution. The reasons were not clear but not thought to be significant in the fibre extrusion when added to alginate dopes.
Referring to
This example describes the preparation of High G or High M based calcium alginate/PVP dopes and their viscosity assessment. For the High G alginate, the 15% w/w dope concentration and weight 400 g contained 5% w/w alginate and 10% w/w PVP. The dope was prepared by first manually mixing 20 g of alginate powder with 40 g of PVP powder and then gradually adding the mixture to 340 g of water that was being stirred vigorously with a high shear mixer. The mixture was stirred continuously for 1 h to ensure a homogeneous dope. The viscosity was then assessed as in Example 1 before and after standing overnight.
The procedure was repeated for High M alginate to obtain the results displayed in Table 2 and
The results indicate the addition of PVP to High G alginate solution appeared to have very little effect on the viscosity and behaviour of the solution even on ageing suggesting that a substantial percentage of PVP could be used if necessary, to potentially change fibre properties. On the other hand, addition of 10% w/w PVP to a 5% w/w High M alginate solution produced a very high viscous dope with tendency to gel on standing. This demonstrates great potential to produce highly absorbent fibres from High M/PVP fibre. However, fibre production may be affected by dope gelation and uncontrollable swelling in the bath. A very low percentage of PVP in the dope may be advantageous.
High G Alginate-PVP Fibres
These examples describe the preparation of High G based calcium alginate/PVP dopes and production of fibres from the dopes.
The dopes were prepared using any of the following general approaches:
A high shear mixer at 3000-4000 rpm was used (forward and/or reverse direction) for 15 minutes before and after addition of powder. The mixer speed was then reduced to 2,000 rpm and left for 30 to 45 minutes depending on dope concentration and viscosity. Once homogeneously mixed, the dope was either vacuum de-aerated or allowed to stand until fully deaerated.
For example, in Example 3, a spinning dope of solid content 8% (w/w) and weight 1,500 g was prepared by mixing together 75 g (5% w/w) sodium alginate powder with 45 g (3% w/w) PVP powder, and then gradually adding the mixed powders to 1380 g of water. The dope was then allowed to stand for three days to deaerate. After viscosity assessment, the dope was passed under pressure through a 25μ cartridge filter and extruded. Similar procedures were repeated for examples 3-7.
Once filtered, each dope was spun through a 90μ/2,000-hole spinneret into a calcium chloride dihydrate coagulation bath and hauled-off whilst simultaneously being washed in water placed under the haul-off rollers. From the haul-off bath, the fibres were stretched through an orientation bath containing acetone/water (56/24, v/v), then washed through successive acetone/water baths at varying compositions before finally washing in pure acetone bath and winding onto a drum roller. The fibres were cut off from the drum roller, hand crimped and then dried at ambient. Table 4 below shows the conditions used to spin each batch and type of fibres obtained.
These examples describe the preparation of High M based calcium alginate/PVP dope and production of fibres from the dope. With reference to Table 5 for the amounts of materials used, the spinning dope of weight 2,000 g was prepared by first, manually mixing together PVP powder and High M sodium alginate powder (High M alginate-Manucol DH supplied by FMC Biopolymers, UK, Ltd) with a spatula. The mixed powders were then gradually added to water stirred continuously with a high shear mixer. Once fully added, the mixture was vigorously mixed to obtain a homogenous dope. The dope was then vacuum de-aerated, filtered under pressure through a 25μ cartridge filter and extruded at 2.7 m/min through a 90μ/2,000-hole spinneret into a 1.6% (w/w) calcium chloride dihydrate coagulation bath. The as-spun fibres were hauled-off at 1.7 m/min from the bath, stretched through acetone/water (56/44, v/v) orientation bath, then washed in series of acetone/water baths (Table 6) before finally washing in pure acetone bath and winding onto a drum roller. The fibres were cut off from the drum roller, hand crimped and then dried under extraction before testing for absorbency.
The following main conclusions were reached:
These examples describe the attempts to prepare fibres from povidone-iodine (PVPI) complex polymer using samples supplied by BASF and Acros. Initially, it was decided to investigate if the complex (PVP-I) could be spun within a reasonable dope concentration. To do this, various concentrations of PVP-I solutions in water were prepared and examined. The solutions were prepared as described in example 1 except that Povidone-iodine (PVP-I) powders supplied by either BASF or Acros were used. The simple rheology of the solutions prepared and their spinnability prospects obtained are outlined below in Table 7.
As expected, the viscosity of PVP-I in aqueous solution increased with increasing concentration of PVP-I in solution. However, the viscosities of the solutions prepared were too low even at 20% PVP-I to be spun. The solutions failed to display any spinnable characteristics as the flows were all in droplets. As shown in
The complex required incorporation of a fibre forming polymer such as alginate for extrusion.
High G Alginate-PVPI fibres
These examples describe the initial attempts to prepare High G alginate-povidone iodine (PVPI) complex fibres. With reference to Table 8 for the amounts of materials used, the spinning dope of weight 2,000 g or 2,500 g was prepared by first, manually mixing together PVP-I powder (30/06 supplied by BASF) and High G sodium alginate powder (High G alginate-Protanal LF10/60 FT supplied by FMC Biopolymers, UK, Ltd) with a spatula. The mixed powders were then gradually added to water that was being stirred continuously with a high shear mixer. Once fully added, the mixture was vigorously mixed for 1 h to 1.5 h depending on dope concentration and viscosity to obtain a homogenous dope. The dope was then vacuum de-aerated, tested for viscosity and pH then filtered under pressure through a 25μ cartridge filter before extruding at 2.36 m/min through a 90p/2,000-hole spinneret into a 1.5% (w/w) calcium chloride dihydrate coagulation bath. The as-spun fibres were hauled-off at 2 m/min from the bath, stretched through acetone/water (56/44, v/v) orientation bath, then washed in series of acetone/water baths (Table 10) before finally washing in pure acetone bath and winding onto a drum roller. The fibres were cut off from the drum roller, hand crimped and then dried under extraction before testing for absorbency and available iodine in the fibre.
As Table 11 appear to show, the fibres produced had good absorbency for high G calcium alginate fibres but low retention which appear to reflect to some extent the effect of PVP in the fibre as observed earlier in examples 6 and 7.
Klebsiella
Staphylococcus
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Staphylococcus aureus
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pneumoniae bacteria
As expected, the fibre contained very low amount of iodine after all the washing processes and therefore no inhibition observed.
Some of the main conclusions from this investigation include:
High M Alginate-PVPI fibres
These examples describe the preparation of spinnable High M sodium alginate-povidone iodine (PVPI) complex solutions using povidone-iodine supplied by Acros or BASF and followed by initial attempts to prepare High M calcium-PVP-I complex fibres from those solutions that can be spun.
Table 13 details the concentrations and amounts of materials used. The solutions were prepared and de-aerated as described in examples 12 and 13 except that in the present examples, High M sodium alginate powder (Manucol DH supplied by FMC Biopolymers, UK, Ltd) and PVP-I powder (30/06 supplied by BASF) or PVP-I powder supplied by Acros were used.
The spinnable dopes were each vacuum de-aerated before extrusion but with extra care for the higher content PVP-I dope (Example 16). This dope was extremely difficult to vacuum deaerate due to excessive foam generated. Deaeration was carried out much slower and in stages before finally leaving to stand overnight to de-vacuum slowly. Each dope was filtered and spun as in examples 12 and 13 except for the spinning conditions shown in Table 15. The viscosity-shear speed profile of High M alginate-PVP-I dopes according to examples 16 and 17 are shown in
Some of the conclusions from this investigation include:
This example describes the extraction of psyllium gel from psyllium seeds and production of calcium alginate—psyllium—PVPI fibres. The psyllium gel was prepared by stirring 205 g of psyllium seeds (supplied by ‘Natural Health 4 Life’ in Devon, www.naturalhealth4life.co.uk) into 5000 g of water (at 80-100° C.). contained in F-20 L Single Layer Glass Reactor (obtained from Zhengzhou Keda machinery & instrument equipment co., Ltd). After addition, stirring continued at 60 rpm for 35 minutes; then 100 g sodium hydroxide solution (5% w/w) was added and stirring increased to 100 rpm for 2 minutes before heating and stirring were stopped to allow the extracted seeds to settle at the bottom of reactor. After standing for 15 minutes and temperature still above 85° C., the reactor discharge valve was opened, first to expel the extracted seeds for disposal, then the psyllium gel (4000 g, pH˜12) decanted through ˜60μ sieve if necessary, into a 10-litre plastic container. At this temperature, one decanting process was enough to separate most of the dissolved mucilage from the seeds as the gel flowed well due to low viscosity. But at lower temperatures (<85° C.), addition of further NaOH solution to reduce viscosity and followed by successive decanting processes were necessary before almost all the gel could be separated from the seeds.
The hot psyllium gel was left to cool (40° C. to ambient), then mixed well with a high shear mixer (at 2500−3500 rpm) until thin and uniform. The gel pH between 11 and 12 (determined using Hanna HI 211 pH/ORP meter) was lowered to between 5 and 6 by addition of 1M HCl.
The alginate-psyllium-PVPI dope was prepared by dissolving 3-5% w/w (typically 60-100 g) alginate (high M or high G or mixture) containing the required amount of PVPI powder (˜0.5% w/w; 10 g) into the psyllium solution (typically 2,000 g; concentration 0.8-1% w/w) using a high shear mixer at 4,000-6,000 rpm for 1-2 h depending on viscosity and solid content. The dope was then transferred into a dope reservoir, vacuum deaerated overnight and spun after viscosity assessment following spinning conditions shown in Table 17.
Some of the conclusions from this investigation include:
Alginate-PVPI-Glycol fibres
These examples describe the attempts made to reduce PVP-I leaching out of fibres during extrusion. The process as indicated in Tables 19-21 involved the modification of Alg./PVI dopes by the addition of non-toxic and easily solvent miscible diols such as propylene glycol (PG, 4-10%) or polyols such as polyethylene glycol (PEG, 0.5-12%) followed by coagulation in 1.5% aqueous calcium chloride solution or in a bath containing˜60% iso-propanol (IPA)/38% water/1.4% calcium chloride/1.3% PEG or in a bath containing 60% water/37% iso-propanol (IPA)/1.5% calcium chloride/1.3% PEG,. Then a post-coagulation treatment was applied using any of the following steps:
The fibres were then dried under low extraction systems after excess liquid was squeezed out. Typically, a batch was prepared from a dope weight of 5,000-6,000 g containing 4.5-6% w/w solids. Dope preparation was as described in examples 12 and 13 except that in the present examples the required solids were first weighed separately, then mixed together properly in dry states before gradually adding to water that was being vigorously stirred with a high shear mixer until all the solids were completely dissolved. This was followed whilst still mixing continuously by a gradual addition of the required amount of PG or PEG and a further mixing for at least 30 minutes to ensure a homogenous dope.
Each dope prepared was as usual vacuum de-aerated, tested for viscosity where necessary (Table 21) and then spun after filtration through a 90μ/2,000-hole spinneret using conditions set out for each example in Table 22. The fibres were cut off from the drum roller, hand crimped and then dried under extraction before testing for absorbency and available iodine in the fibre.
The potential controlling effects of the glycols (PG and PEG) on the ‘leaching-out’ of PVPI from fibres during extrusion and possibly also post extrusion, was also investigated by incorporating non-complex iodine into fibres and felts through:
The dope preparations and extrusion were carried out as described in examples 20-24 for alginate-PVPI-glycol fibres except that 0.5% w/w iodine crystals (supplied by Alfa Aesar, mp 183-186° C., mol. wt (or FW) 253.81, density 4.930 g/cm3) were used in place of PVPI. Small amounts of PG or PEG were ground using mortal/pestle before adding to the dope and mixing homogeneously to give very dark dope solutions. Dopes were either vacuum deaerated or sealed and left standing to deaerate overtime. Vacuum deaeration as expected led to rapid escape of iodine from the dope. Extrusion was satisfactory except for partial gelation of dopes.
Fibres produced had deep iodine colour initially, but this faded very quickly on exposure to air and even after sealing, the iodine gradually vaporised out of the fibres leaving it colourless. Addition of PG or PEG retarded evaporation but did not stop it. Similar problems were observed when producing the final materials using a ‘dyeing’ process in place of the extrusion process as described herein.
Some of the conclusions from this investigation include:
Unless defined otherwise all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the presently described subject matter pertains.
Where a range of values is provided, for example, concentration ranges, percentage ranges, or ratio ranges, it is understood that each intervening value, to the tenth of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the described subject matter. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and such embodiments are also encompassed within the described subject matter, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the described subject matter.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1915425.1 | Oct 2019 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2020/052662 | 10/22/2020 | WO |
