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WO2018184050A1 - A nonwoven web designed for use in a wound care product - Google Patents

A nonwoven web designed for use in a wound care product Download PDF

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Publication number
WO2018184050A1
WO2018184050A1 PCT/AT2017/000031 AT2017000031W WO2018184050A1 WO 2018184050 A1 WO2018184050 A1 WO 2018184050A1 AT 2017000031 W AT2017000031 W AT 2017000031W WO 2018184050 A1 WO2018184050 A1 WO 2018184050A1
Authority
WO
WIPO (PCT)
Prior art keywords
nonwoven material
nonwoven
wound care
care product
filaments
Prior art date
Application number
PCT/AT2017/000031
Other languages
French (fr)
Inventor
Tom Carlyle
Mirko Einzmann
Gisela Goldhalm
Malcolm John Hayhurst
Katharina Mayer
Ibrahim SAGERER-FORIC
Original Assignee
Lenzing Ag
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lenzing Ag filed Critical Lenzing Ag
Priority to PCT/AT2017/000031 priority Critical patent/WO2018184050A1/en
Publication of WO2018184050A1 publication Critical patent/WO2018184050A1/en

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Classifications

    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/425—Cellulose series
    • D04H1/4258—Regenerated cellulose series
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B32B5/022—Non-woven fabric
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B32B5/06—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer characterised by a fibrous or filamentary layer mechanically connected, e.g. by needling to another layer, e.g. of fibres, of paper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
    • B32B5/24—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer
    • B32B5/26—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer another layer next to it also being fibrous or filamentary
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    • B32B7/04—Interconnection of layers
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    • B32B7/04—Interconnection of layers
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    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/4374—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece using different kinds of webs, e.g. by layering webs
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
    • D04H3/013—Regenerated cellulose series
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/02—2 layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
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    • B32B2250/03—3 layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/04—4 layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/05—5 or more layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/20—All layers being fibrous or filamentary
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
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    • B32B2260/00—Layered product comprising an impregnated, embedded, or bonded layer wherein the layer comprises an impregnation, embedding, or binder material
    • B32B2260/02—Composition of the impregnated, bonded or embedded layer
    • B32B2260/021—Fibrous or filamentary layer
    • B32B2260/023—Two or more layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B32B2260/00—Layered product comprising an impregnated, embedded, or bonded layer wherein the layer comprises an impregnation, embedding, or binder material
    • B32B2260/04—Impregnation, embedding, or binder material
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    • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
    • B32B2262/04—Cellulosic plastic fibres, e.g. rayon
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    • B32B2262/06—Vegetal fibres
    • B32B2262/062—Cellulose fibres, e.g. cotton
    • B32B2262/065—Lignocellulosic fibres, e.g. jute, sisal, hemp, flax, bamboo
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Definitions

  • This invention relates to a nonwoven web suitable to be used in an absorbent wound care product, and, more particularly, to an essentially pure cellulose nonwoven web formed from essentially continuous filaments and multibonded by merged filaments, hydrogen bonding and/or physical intermingling of filaments.
  • essentially pure cellulose shall address the fact that cellulosic moulded bodies, e.g. made according to the lyocell process, always contain a small amount of polymers other than cellulose, namely hemicellulose. This does not influence in any way the suitability for the use according to this invention.
  • This multibonded web provides absorbency of wound exudate at a wide pH range, physical padding or protection for a wound, and physical integrity and strength even when saturated to permit and facilitate clean removal. Further, it is important for such a wound care product to be based on a renewable resource, be inexpensive and biodegradable.
  • This invention further relates to additional bonding of this web to other webs or materials through
  • U.S. 6,838,590 describes an airlaid nonwoven used as an absorbent wound care pad
  • U.S. 6,075,177 describes the use of nonwovens based on carboxymethyl cellulose fibers for wound care products
  • U.S. 6,146,892 describes a nonwoven used as a scaffold for cell growth for use in wound care
  • U.S. 6,153,214 describes a needlepunch, spunlace or carded nonwoven used as reinforcement for a wound care product
  • U.S. 6,235,964 describes a nonwoven used as a backing for a wound care product
  • U.S. 6,759,567 describes an airlaid pulp nonwoven used as an absorbent pad in a wound care product
  • U.S. 9,297,099 describes a nonwoven based on tow filament fiber product for use in wound care. All of these describe nonwovens or composites used for or in wound care products.
  • U.S. 6,838,590 describes an airlaid nonwoven useful for wound care, which has absorbency, and is based on renewable materials but has limited physical strength, integrity and the ability to be removed from a wound without causing damage to the healing wound.
  • U.S. 8,808,594 describes a coform nonwoven with strength and physical integrity, but lower absorbency and cushioning ability and has a significant percentage on non-renewable, non-biodegradable raw materials.
  • the present invention relates to the use of specially designed nonwoven substrates produced using novel variants of the spunlaid nonwoven process, comprising essentially pure cellulose polymers.
  • spunlaid cellulose webs There are known methods and products using spunlaid cellulose webs.
  • Wound care products must combine absorbency at all pHs with strength, physical integrity, and the ability to enhance healing of a wound while being composed of sustainable and biodegradable materials.
  • the problem with current wound care products is that none addresses all of the needs.
  • the most prevalent solution is to either combine two separate nonwovens or materials; one with strength and physical integrity and one with absorbency. Usually one is sustainable while the other is not. This is both expensive and inadequate, as the result is an average of the two materials, where the absorbent material is not strong and the strong material is not absorbent or biodegradable. An optimal solution is not available.
  • the nonwoven material according to the invention has absorbency at all pHs, high physical integrity, can prevent contamination and physical damage to a wound, can be removed from a wound without damage or interference with healing, and is biodegradable, compostable and based on renewable resources.
  • the nonwoven web which is a 100% essentially continuous filament cellulose nonwoven will provide both high strength/physical integrity and high absorbency, and as a sustainable product.
  • the current invention can substitute for multi-layer structures, that use airlaid and/or meltblown webs for absorbency and other layers for strength, providing both the same absorbency and physical strength and integrity in a single biodegradable and sustainable product.
  • the first cellulosic nonwoven web is preferably made according to a lyocell process.
  • Cellulosic fibres can be produced by various processes.
  • a lyocell fibre is spun from cellulose dissolved in N-methyl morpholine N-oxide (NMMO) by a meltblown process, in principle known from e.g. EP 1093536 B1 , EP 2013390 B1 and EP 2212456 B1.
  • meltblown it will be understood that it refers to a process that is similar or analogous to the process used for the production of synthetic thermoplastic fibres (filaments are extruded under pressure through nozzles and stretched to required degree by high velocity/high temperature extension air flowing substantially parallel to the filament direction), even though the cellulose is dissolved in solution (i.e.
  • the web is formed by a spun bonding process, where filaments are stretched via lower temperature air.
  • spunbonded synthetic fibres are longer than meltblown synthetic fibres which usually come in discrete shorter lengths. Fibres formed by the solution blown lyocell process can be continuous or discontinuous depending on process conditions such as extension air velocity, air pressure, air temperature, viscosity of the solution, cellulose molecular weight and distribution and combinations thereof.
  • the fibres are contacted with a non-solvent such as water (or water/NMMO mixture) by spraying, after extrusion but before web formation.
  • a non-solvent such as water (or water/NMMO mixture)
  • the fibres are subsequently taken up on a moving foraminous support to form a nonwoven web, washed and dried.
  • Freshly-extruded lyocell solution ('solvent spun', which will contain only, for example, 5-15% cellulose) behaves in a similar way to 'sticky' and deformable thermoplastic filaments. Causing the freshly-spun filaments to contact each other while still swollen with solvent and with a 'sticky' surface under even low pressure will cause merged filament bonding, where molecules from one filament mix irreversibly with molecules from a different filament. Once the solvent is removed and coagulation of filaments completed, this type of bonding is impossible.
  • coagulation liquor i.e. a liquid which is able to cause coagulation of the dissolved cellulose; in a lyocell process this preferably is water or a diluted solution of NMMO in water, is applied to control the merged filament bonding.
  • the amount of merged filament bonding is directly dependent on the stage of coagulation of the filaments when the filaments come into contact. The earlier in the coagulation process that the filaments come into contact, the greater the degree of filament merging that is possible. Both placement of the coagulation liquor application and the speed at which the application liquor is applied can either increase, or decrease, the rate of coagulation. Which results in control of the degree (or amount) of merged filament bonding that occurs in the material.
  • the merged filament bonding is further controlled by filament spinning nozzle design and arrangement and the configuration and temperature of filament extension air.
  • the degree of molecular alignment that is present as the solution exits the spinning nozzle has an impact on the coagulation rate. The more aligned the molecules are, the faster the coagulation rate, and conversely, the less aligned the molecules are, the slower the coagulation rate.
  • the spinning nozzle design and arrangement, along with the molecular weight of the cellulosic raw material used will determine the starting coagulation rate at the exit of the spinning nozzle. Additionally, the rate of cooling (temperature decrease) of the solution upon spinning nozzle exit will impact the coagulation rate as well.
  • At least two spinnerets also known as jets
  • spinnerets preferably between two and ten, and further preferred between 2 and 6, each one arranged to form a layer of nonwoven web
  • spinnerets are used to obtain a multilayer nonwoven material.
  • the filaments are spun using a solution of cellulose in an aqueous amine oxide and the coagulation liquor is water, preferably with a content of amine oxide not being able to dissolve cellulose, also referred to as a lyocell process; the manufacture of such a solution is in principle known, e.g. from U.S. 6,358,461 , U.S. 7,067,444, U.S. 8,012,565, U.S. 8,191 ,214, U.S.
  • the present invention describes a cellulosic nonwoven web produced via a meltblown or spunbond-type process.
  • the filaments produced are subjected to touching and/or compaction and/or intermingling at various points in the process, particularly before and during initial web formation.
  • Contact between filaments where a high proportion of solvent is still present and the filaments are still swollen with said solvent causes merged filament bonding to occur.
  • the amount of solvent present as well as temperature and contact pressure controls the amount of this bonding.
  • the amount of filament intermingling and hydrogen bonding can be limited by the degree of merged filament bonding.
  • This is the result of a decrease in filament surface area and a decrease in the degree of flexibility of the filaments.
  • the degree of merged filament bonding increase, the amount of overall surface area is decreased, and the ability of cellulose to form hydrogen bonds is directly dependent on the amount of hydroxyl groups present on the cellulosic surface.
  • filament intermingling happens as the filaments contact the forming belt. The filaments are traveling at a faster rate of speed than the forming belt. Therefore, as the filament contacts the belt, it will buckle and sway side to side, and back and forth, just above the forming belt.
  • the filaments will intermingle with neighboring filaments. If the filaments touch and merge prior to the forming belt, this limits the number of neighboring filaments by which it can intermingle with. Additionally, filaments that merge prior to contacting the forming belt with not have the same degree of flexibility as a single filament and this will limit the total area over which the filament will buckle and sway.
  • the nonwoven material is dried prior to subsequent bonding/treatment.
  • the percentage of each type of bonding is controlled using a process with up to two compaction steps, where one of these compaction steps is done after step d. of the inventive process where the spun filaments are still swollen with a solvent, and one of these compaction steps is done before or in step e. of the inventive process where all or most of the solvent has been removed and the web has been wet with water.
  • control of the coagulation of the spun solution is a factor in controlling the degree of merged filament bonding.
  • This preferred embodiment concerns decreasing the coagulation rate to a state where additional compaction steps can be used after filament laydown to further increase the actual amount of merged filament boding that is achievable. It might be helpful to view the maximum achievable filament bonding as the state where we have merged all filaments into an essentially film-like structure.
  • the present invention describes a process and product where merged filament bonding, physical intermingling and hydrogen bonding can be controlled independently.
  • the degree of merged filament bonding can limit the degree of physical intermingling and hydrogen bonding that can occur.
  • process conditions can be adjusted to optimise these bonding mechanisms between layers. This can include modifying ease of delamination of layers, if required.
  • bonding/treatment steps may optionally be added. These bonding/treatment steps may occur while the web is still wet with water, or dried (either fully or partially).
  • bonding/treatment steps may add additional bonding and/or other web property modification.
  • These other bonding/treatment steps include hydroentangling or spunlacing, needling or needlepunching, adhesive or chemically bonding.
  • various post- treatments to the web may also be applied to achieve specific product performance.
  • post-treatments it is possible to apply finishes and other chemical treatments directly to the web of this invention during production which will not then be removed, as occurs with, for example, a post-treatment hydroentanglement step.
  • Varying the degree of merged filament bonding provides unique property characteristics for nonwoven cellulose webs with regards to softness, stiffness, dimensional stability and various other properties. Properties may also be modified by altering the degree of physical intermingling before and during initial web formation. It is also possible to influence hydrogen bonding, but the desired effect of this on web properties is minor. Additionally, properties can be adjusted further by including an additional
  • bonding/treatment step such as hydroentangling, needlepunching, adhesive bonding and/or chemical bonding.
  • Each type of bonding/treatment provides benefits to the nonwoven web.
  • hydroentangling can add some strength and soften the web as well as potentially modifying bulk density; needling is typically employed for higher basis weights and used to provide additional strength; adhesive and chemical bonding can add both strength and surface treatments, like abrasive material, tackifiers, or even surface lubricants.
  • the present invention allows independent control of the key web bonding features: merged filaments, intermingling at web formation, hydrogen bonding and optional additional downstream processing. Manipulation of merged filament bonding can be varied to predominantly dictate the properties of the nonwoven web.
  • the nonwoven web is hydroentangled in a subsequent process step.
  • Hydroentangling is in principle commonly known.
  • the basis weight of the nonwoven material is between 50 and 300 grams per square meter.
  • the nonwoven material contains a second layer, consisting of a ceilulosic nonwoven web, which is formed of essentially continuous filaments, pulp fiber or staple fiber, is formed on top of the first ceilulosic nonwoven web, and subsequently both layers are hydroentangled together.
  • a ceilulosic nonwoven web which is formed of essentially continuous filaments, pulp fiber or staple fiber, is formed on top of the first ceilulosic nonwoven web, and subsequently both layers are hydroentangled together.
  • the nonwoven material contains a third web, consisting of a ceilulosic nonwoven, which is formed of essentially continuous filaments, pulp fiber or staple fiber, is formed on top, and subsequently all three layers are hydroentangled together.
  • a ceilulosic nonwoven which is formed of essentially continuous filaments, pulp fiber or staple fiber, is formed on top, and subsequently all three layers are hydroentangled together.
  • another useful advantage is to have the outer webs designed to provide the strength and designed to minimize linting with the center web designed to have a high absorbent capacity. This would enable the product to be more easily removed from the wound site without irritation by lint, or risk of infection by loose particles left behind after removal of the absorbent wound care pad.
  • the number of layers is at least two, preferably between two and ten, with a further preferred range from 2 to 6 layers.
  • Some or even all, preferably all of the layers according to this embodiment of the invention are formed of essentially continuous filaments, pulp fiber or staple fiber and subsequently some or even all, preferably all layers are bonded together using merged filament bonding, hydrogen bonding and/or filament intermingling.
  • some or even all, preferably all of the layers according to this embodiment of the invention are formed of essentially continuous filaments, pulp fiber or staple fiber and subsequently some or even all, preferably all layers are hydroentangled together.
  • Multi-web structures can be designed such that better utilization of the absorbent wound product can be achieved.
  • wick (spread) fluids faster in the x and y directions closer to the wound site we can also design other webs that will inhibit wicking (spreading) on the outside (farthest from the wound site). This limited wicking on the outer web will allow for decrease leakage from the absorbent wound care product.
  • one or more of the cellulosic nonwoven layers within the nonwoven material, if formed of essentially continuous filaments, are made according to a lyocell process.
  • the lyocell process allows for use of a sustainable raw material (pulp) and provides a final filament with high purity.
  • the nonwoven material contains an antibacterial chemical impregnation that will aid with infection prevention.
  • These chemicals can be applied to any of the cellulosic nonwoven web layers or to the nonwoven material before finally processed into the wound care product, but preferably, they are applied to the final absorbent wound care product material.
  • These chemical surface treatments would consist of any chemistry that is known to kill bacteria, disinfect skin, or generally clean skin.
  • the most commonly used chemicals used today for such purposes are belonging to the group containing BZK (Benzalkonium chloride), CHG (Cholorohexidine gluconate) and betadiene. This will maximize the ability of the wound to heal while minimizing the risk of infection.
  • the use according to the invention includes the addition of an antibacterial chemical impregnation to the nonwoven material during the manufacture of the absorbent wound care product.
  • the nonwoven material of the compostable absorbent wound care product is further processed by hydroentanglement. Undergoing this additional process enables a greater range of material functionality design. Such attributes as thickness, drape, softness, strength and aesthetic appearance can be modified to meet specific wound care requirements
  • a 38-gsm product of the invention was compared in terms of stiffness to a commercial absorptive woundcare product of 27 gsm. Even though the product of invention was higher in basis weight, meaning that more material for absorption of wound exudate is present, the product of invention had 35% less overall stiffness, meaning it is much more comfortable to wear and offers a better fit to body surface.
  • Stiffness was measured using a 'Handle-o-meter', according to standard method WSP 90.3, with 1 ⁇ 4 inch slot width, stainless steel surface, 1000 g beam. Sample size was to 10 x 10 cm.
  • the 38 gsm product of invention of example 1 was tested for wicking (or spread ability) of liquid versus a commercial woundcare product of the same basis weight, comprised of cellulosic staple fiber. Horizontal spread of liquid is an important feature of woundcare products as otherwise local overloading of the woundcare product with wound exudate can occur, followed by leaking.
  • test method was as follows. Samples were conditioned at 23°C ⁇ 2°C and relative humidity 50% ⁇ 5% for 24 hours. 0.5 ml of test liquid (water with 2g/L of Sulfacide brilliant green dye) was pipetted onto the sample using an
  • the fabric of the invention achieved a 14% greater spread area than the commercial sample.

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Abstract

This invention relates to a nonwoven material for use in an absorbent wound care product, that comprises essentially pure cellulosic nonwoven web produced as essentially continuous filaments, has absorbency at all pHs, high physical integrity, can prevent contamination and physical damage to a wound, can be removed from a wound without damage or interference with healing, and is biodegradable, compostable and based on renewable resources. It further relates to the use of the inventive material wherein the manufacture of an absorbent wound care product includes the addition of an antibacterial chemical impregnation to the nonwoven material.

Description

A nonwoven web designed for use in a wound care product
This invention relates to a nonwoven web suitable to be used in an absorbent wound care product, and, more particularly, to an essentially pure cellulose nonwoven web formed from essentially continuous filaments and multibonded by merged filaments, hydrogen bonding and/or physical intermingling of filaments.
The term "essentially pure cellulose" shall address the fact that cellulosic moulded bodies, e.g. made according to the lyocell process, always contain a small amount of polymers other than cellulose, namely hemicellulose. This does not influence in any way the suitability for the use according to this invention.
This multibonded web provides absorbency of wound exudate at a wide pH range, physical padding or protection for a wound, and physical integrity and strength even when saturated to permit and facilitate clean removal. Further, it is important for such a wound care product to be based on a renewable resource, be inexpensive and biodegradable. This invention further relates to additional bonding of this web to other webs or materials through
hydroentangling to enhance these key performance properties needed in a wound care product.
Prior Art
The use of nonwovens in wound care products is well known. U.S. 6,838,590 describes an airlaid nonwoven used as an absorbent wound care pad, U.S. 6,075,177 describes the use of nonwovens based on carboxymethyl cellulose fibers for wound care products, U.S. 6,146,892 describes a nonwoven used as a scaffold for cell growth for use in wound care, U.S. 6,153,214 describes a needlepunch, spunlace or carded nonwoven used as reinforcement for a wound care product, U.S. 6,235,964 describes a nonwoven used as a backing for a wound care product, U.S. 6,759,567 describes an airlaid pulp nonwoven used as an absorbent pad in a wound care product, U.S. 8,808,594 describes a coform nonwoven of spunlaid and absorbent fibers used as an absorbent component in a wound care product, U.S. 9,144,625 and U.S. 9,221 ,963 describe carded and needlepunched cellulose alkonyl sulfonate for wound care products, U.S. 9,492,171 describes a nonwoven used as one
component in a wound care product and U.S. 9,297,099 describes a nonwoven based on tow filament fiber product for use in wound care. All of these describe nonwovens or composites used for or in wound care products.
There has been significant research in nonwovens for wound care products but the current technology is not yet optimal. The current technology recognizes the need for absorbency of exudates in wound care products, as well as absorbency at a wide range of pH, the ability to keep wounds moist, the ability to protect a wound from contamination as well as physical force, and the ability to be in contact with wounds but still be removable without damaging the healing wound. There is also a need for physical strength, integrity and dimensional stability and a strong desire for products which are based on renewable and sustainable materials and which are biodegradable.
Previous technology has addressed one or more of these issues, but not all. U.S. 6,838,590 describes an airlaid nonwoven useful for wound care, which has absorbency, and is based on renewable materials but has limited physical strength, integrity and the ability to be removed from a wound without causing damage to the healing wound. U.S. 8,808,594 describes a coform nonwoven with strength and physical integrity, but lower absorbency and cushioning ability and has a significant percentage on non-renewable, non-biodegradable raw materials.
The present invention relates to the use of specially designed nonwoven substrates produced using novel variants of the spunlaid nonwoven process, comprising essentially pure cellulose polymers. There are known methods and products using spunlaid cellulose webs. U.S. 6,358,461 , U.S. 7,067,444, U.S. 8,012,565, U.S. 8,191 ,214, U.S. 8,263,506 and U.S. 8,318,318 all teach methods for producing and using spunlaid cellulose webs. None of these teaches production methods for, or products, addressing the specific substrate requirements for wound care products. Problem
Wound care products must combine absorbency at all pHs with strength, physical integrity, and the ability to enhance healing of a wound while being composed of sustainable and biodegradable materials.
The problem with current wound care products is that none addresses all of the needs. The most prevalent solution is to either combine two separate nonwovens or materials; one with strength and physical integrity and one with absorbency. Usually one is sustainable while the other is not. This is both expensive and inadequate, as the result is an average of the two materials, where the absorbent material is not strong and the strong material is not absorbent or biodegradable. An optimal solution is not available.
There is distinct need for a biodegradable, sustainably produced strong, absorbent nonwoven substrate for use in wound care products.
Description
It is the object of the present invention to provide a nonwoven material to be used in an absorbent wound care product, that comprises at least one essentially pure cellulosic nonwoven web produced as essentially continuous filaments. Due to the process of their manufacture the filaments are
multibonded by merged filaments, hydrogen bonding and/or physical intermingling of filaments. The nonwoven material according to the invention has absorbency at all pHs, high physical integrity, can prevent contamination and physical damage to a wound, can be removed from a wound without damage or interference with healing, and is biodegradable, compostable and based on renewable resources. The nonwoven web which is a 100% essentially continuous filament cellulose nonwoven will provide both high strength/physical integrity and high absorbency, and as a sustainable product.
In one embodiment, the current invention can substitute for multi-layer structures, that use airlaid and/or meltblown webs for absorbency and other layers for strength, providing both the same absorbency and physical strength and integrity in a single biodegradable and sustainable product. The first cellulosic nonwoven web is preferably made according to a lyocell process.
Cellulosic fibres can be produced by various processes. In one embodiment a lyocell fibre is spun from cellulose dissolved in N-methyl morpholine N-oxide (NMMO) by a meltblown process, in principle known from e.g. EP 1093536 B1 , EP 2013390 B1 and EP 2212456 B1. Where the term meltblown is used it will be understood that it refers to a process that is similar or analogous to the process used for the production of synthetic thermoplastic fibres (filaments are extruded under pressure through nozzles and stretched to required degree by high velocity/high temperature extension air flowing substantially parallel to the filament direction), even though the cellulose is dissolved in solution (i.e. not a molten thermoplastic) and the spinning & air temperatures are only moderately elevated. Therefore the term "solution blown" may be even more appropriate here instead of the term "meltblown" which has already become somewhat common for these kinds of technologies. For the purposes of the present invention both terms can be used synonymously. In another embodiment the web is formed by a spun bonding process, where filaments are stretched via lower temperature air. In general, spunbonded synthetic fibres are longer than meltblown synthetic fibres which usually come in discrete shorter lengths. Fibres formed by the solution blown lyocell process can be continuous or discontinuous depending on process conditions such as extension air velocity, air pressure, air temperature, viscosity of the solution, cellulose molecular weight and distribution and combinations thereof.
In one embodiment for making a nonwoven web the fibres are contacted with a non-solvent such as water (or water/NMMO mixture) by spraying, after extrusion but before web formation. The fibres are subsequently taken up on a moving foraminous support to form a nonwoven web, washed and dried.
Freshly-extruded lyocell solution ('solvent spun', which will contain only, for example, 5-15% cellulose) behaves in a similar way to 'sticky' and deformable thermoplastic filaments. Causing the freshly-spun filaments to contact each other while still swollen with solvent and with a 'sticky' surface under even low pressure will cause merged filament bonding, where molecules from one filament mix irreversibly with molecules from a different filament. Once the solvent is removed and coagulation of filaments completed, this type of bonding is impossible.
It is another object of the present invention to provide a process for the manufacture of a nonwoven material consisting of essentially continuous cellulosic filaments by:
a. Preparation of a cellulose-containing spinning solution
b. Extrusion of the spinning solution through at least one spinneret containing closely-spaced meltblown jet nozzles
c. Attenuation of the extruded spinning solution using high velocity air streams,
d. Forming of the web onto a moving surface [e.g. a perforated belt or drum], e. Washing of the formed web
f . Drying of the washed web
wherein in step c. and/or d. coagulation liquor, i.e. a liquid which is able to cause coagulation of the dissolved cellulose; in a lyocell process this preferably is water or a diluted solution of NMMO in water, is applied to control the merged filament bonding. The amount of merged filament bonding is directly dependent on the stage of coagulation of the filaments when the filaments come into contact. The earlier in the coagulation process that the filaments come into contact, the greater the degree of filament merging that is possible. Both placement of the coagulation liquor application and the speed at which the application liquor is applied can either increase, or decrease, the rate of coagulation. Which results in control of the degree (or amount) of merged filament bonding that occurs in the material.
Preferably the merged filament bonding is further controlled by filament spinning nozzle design and arrangement and the configuration and temperature of filament extension air. The degree of molecular alignment that is present as the solution exits the spinning nozzle has an impact on the coagulation rate. The more aligned the molecules are, the faster the coagulation rate, and conversely, the less aligned the molecules are, the slower the coagulation rate. The spinning nozzle design and arrangement, along with the molecular weight of the cellulosic raw material used will determine the starting coagulation rate at the exit of the spinning nozzle. Additionally, the rate of cooling (temperature decrease) of the solution upon spinning nozzle exit will impact the coagulation rate as well. The slower the cooling rate, the slower the coagulation rate, and conversely, the faster the cooling rate, the faster the coagulation rate. Therefore, configuration of the filament extension air can directing impact the cooling rate and therefore, impact the coagulation rate, which impacts the achievable amount of merged filament bonding that is possible.
In a preferred embodiment of the process according to the invention at least two spinnerets (also known as jets), preferably between two and ten, and further preferred between 2 and 6, each one arranged to form a layer of nonwoven web, are used to obtain a multilayer nonwoven material. By applying different process conditions at the individual spinnerets it is even possible to obtain a multilayer nonwoven material wherein the individual layers have different properties. This may be useful to optimize the nonwoven material according to the invention for different applications. In one
embodiment this could provide a gradient of filament diameters from one side of the material to the other side by having each individual web having a standard filament diameter that is less than the web on top, it is possible to create a material suitable for use as an air filter media that will provide a gradient of pore size (particle size capture). This will provide an efficient filtration process and result in a lower pressure drop across the filter media compared to a single web with similar characteristics at the same basis weight and pore size distribution.
Preferably the filaments are spun using a solution of cellulose in an aqueous amine oxide and the coagulation liquor is water, preferably with a content of amine oxide not being able to dissolve cellulose, also referred to as a lyocell process; the manufacture of such a solution is in principle known, e.g. from U.S. 6,358,461 , U.S. 7,067,444, U.S. 8,012,565, U.S. 8,191 ,214, U.S.
8,263,506 and U.S. 8,318,318; preferably the amine oxide is NMMO. The present invention describes a cellulosic nonwoven web produced via a meltblown or spunbond-type process. The filaments produced are subjected to touching and/or compaction and/or intermingling at various points in the process, particularly before and during initial web formation. Contact between filaments where a high proportion of solvent is still present and the filaments are still swollen with said solvent causes merged filament bonding to occur. The amount of solvent present as well as temperature and contact pressure (for example resulting from extension air) controls the amount of this bonding.
In particular the amount of filament intermingling and hydrogen bonding can be limited by the degree of merged filament bonding. This is the result of a decrease in filament surface area and a decrease in the degree of flexibility of the filaments. For instance, as the degree of merged filament bonding increase, the amount of overall surface area is decreased, and the ability of cellulose to form hydrogen bonds is directly dependent on the amount of hydroxyl groups present on the cellulosic surface. Additionally, filament intermingling happens as the filaments contact the forming belt. The filaments are traveling at a faster rate of speed than the forming belt. Therefore, as the filament contacts the belt, it will buckle and sway side to side, and back and forth, just above the forming belt. During this buckling and swaying, the filaments will intermingle with neighboring filaments. If the filaments touch and merge prior to the forming belt, this limits the number of neighboring filaments by which it can intermingle with. Additionally, filaments that merge prior to contacting the forming belt with not have the same degree of flexibility as a single filament and this will limit the total area over which the filament will buckle and sway.
Surprisingly, it has been found that high levels of control of filament merging can be achieved by modifying key process variables. In addition, physical intermingling of at least partially coagulated cellulose filaments can occur after initial contact with non-solvent, particularly at initial filament laydown to form the web. It arises from the potential of the essentially continuous filaments to move laterally during initial filament formation and initial laydown. Degree of physical intermingling is influenced by process conditions such as residual extension air velocity at the foraminous support (forming belt). It is completely different from the intermingling used in production of webs derived from cellulose staple fibers. For staple fibers, an additional process step such as calendaring is applied after the web has been formed. Filaments which still contain some residual solvent are weak, tender and prone to damage.
Therefore, in combination with controlling degree and type of bonding at this stage, it is essential that process conditions are not of a type which could cause filament and web damage. Initial drying of the washed but never-dried nonwoven, together with optionally compacting, will cause additional hydrogen bonding between filaments to develop. Modifying temperature, compacting pressure or moisture levels can control the degree of this hydrogen bonding. Such treatment has no effect on intermingling or the merged filament bonding.
In a preferred embodiment of the invention the nonwoven material is dried prior to subsequent bonding/treatment.
In a preferred embodiment of the invention the percentage of each type of bonding is controlled using a process with up to two compaction steps, where one of these compaction steps is done after step d. of the inventive process where the spun filaments are still swollen with a solvent, and one of these compaction steps is done before or in step e. of the inventive process where all or most of the solvent has been removed and the web has been wet with water. As previously discussed, control of the coagulation of the spun solution is a factor in controlling the degree of merged filament bonding. This preferred embodiment concerns decreasing the coagulation rate to a state where additional compaction steps can be used after filament laydown to further increase the actual amount of merged filament boding that is achievable. It might be helpful to view the maximum achievable filament bonding as the state where we have merged all filaments into an essentially film-like structure.
The present invention describes a process and product where merged filament bonding, physical intermingling and hydrogen bonding can be controlled independently. However, the degree of merged filament bonding can limit the degree of physical intermingling and hydrogen bonding that can occur. In addition, for the production of multi-layer web products, process conditions can be adjusted to optimise these bonding mechanisms between layers. This can include modifying ease of delamination of layers, if required.
In addition to merged filament, intermingling and hydrogen bonding being independently set as described above, additional bonding/treatment steps may optionally be added. These bonding/treatment steps may occur while the web is still wet with water, or dried (either fully or partially). These
bonding/treatment steps may add additional bonding and/or other web property modification. These other bonding/treatment steps include hydroentangling or spunlacing, needling or needlepunching, adhesive or chemically bonding. As will be familiar to those skilled in the art, various post- treatments to the web may also be applied to achieve specific product performance. By contrast, when post-treatments are not required, it is possible to apply finishes and other chemical treatments directly to the web of this invention during production which will not then be removed, as occurs with, for example, a post-treatment hydroentanglement step.
Varying the degree of merged filament bonding provides unique property characteristics for nonwoven cellulose webs with regards to softness, stiffness, dimensional stability and various other properties. Properties may also be modified by altering the degree of physical intermingling before and during initial web formation. It is also possible to influence hydrogen bonding, but the desired effect of this on web properties is minor. Additionally, properties can be adjusted further by including an additional
bonding/treatment step such as hydroentangling, needlepunching, adhesive bonding and/or chemical bonding. Each type of bonding/treatment provides benefits to the nonwoven web. For example, hydroentangling can add some strength and soften the web as well as potentially modifying bulk density; needling is typically employed for higher basis weights and used to provide additional strength; adhesive and chemical bonding can add both strength and surface treatments, like abrasive material, tackifiers, or even surface lubricants. The present invention allows independent control of the key web bonding features: merged filaments, intermingling at web formation, hydrogen bonding and optional additional downstream processing. Manipulation of merged filament bonding can be varied to predominantly dictate the properties of the nonwoven web.
Preferably the nonwoven web is hydroentangled in a subsequent process step. Hydroentangling is in principle commonly known.
Preferably the basis weight of the nonwoven material is between 50 and 300 grams per square meter.
5# In a further preferred embodiment of the invention the nonwoven material contains a second layer, consisting of a ceilulosic nonwoven web, which is formed of essentially continuous filaments, pulp fiber or staple fiber, is formed on top of the first ceilulosic nonwoven web, and subsequently both layers are hydroentangled together. One useful advantage of two webs is that one web can be designed such that it provides the strength need for the application, while the other web is designed to provide the absorbency and overall fluid management.
In a further preferred embodiment of the invention the nonwoven material contains a third web, consisting of a ceilulosic nonwoven, which is formed of essentially continuous filaments, pulp fiber or staple fiber, is formed on top, and subsequently all three layers are hydroentangled together. Here, another useful advantage is to have the outer webs designed to provide the strength and designed to minimize linting with the center web designed to have a high absorbent capacity. This would enable the product to be more easily removed from the wound site without irritation by lint, or risk of infection by loose particles left behind after removal of the absorbent wound care pad.
In the same way nonwoven materials with even more layers of webs are possible. The number of layers is at least two, preferably between two and ten, with a further preferred range from 2 to 6 layers. Some or even all, preferably all of the layers according to this embodiment of the invention are formed of essentially continuous filaments, pulp fiber or staple fiber and subsequently some or even all, preferably all layers are bonded together using merged filament bonding, hydrogen bonding and/or filament intermingling.
In another preferred embodiment some or even all, preferably all of the layers according to this embodiment of the invention are formed of essentially continuous filaments, pulp fiber or staple fiber and subsequently some or even all, preferably all layers are hydroentangled together.
Horizontal spread of liquid is an important feature of woundcare products as otherwise local overloading of the woundcare product with wound exudate can occur, followed by leaking. In a further preferred embodiment, multi-web structures can be designed such that better utilization of the absorbent wound product can be achieved. By providing webs that wick (spread) fluids faster in the x and y directions closer to the wound site, we can also design other webs that will inhibit wicking (spreading) on the outside (farthest from the wound site). This limited wicking on the outer web will allow for decrease leakage from the absorbent wound care product.
In especially preferred embodiments of the invention one or more of the cellulosic nonwoven layers within the nonwoven material, if formed of essentially continuous filaments, are made according to a lyocell process. As known to an expert in the art, the lyocell process allows for use of a sustainable raw material (pulp) and provides a final filament with high purity.
It is another object of the present invention to provide an absorbent wound care product which contains a nonwoven material according to claim 1 as a base sheet.
In a further preferred embodiment of the invention, the nonwoven material contains an antibacterial chemical impregnation that will aid with infection prevention. These chemicals can be applied to any of the cellulosic nonwoven web layers or to the nonwoven material before finally processed into the wound care product, but preferably, they are applied to the final absorbent wound care product material. These chemical surface treatments would consist of any chemistry that is known to kill bacteria, disinfect skin, or generally clean skin. The most commonly used chemicals used today for such purposes are belonging to the group containing BZK (Benzalkonium chloride), CHG (Cholorohexidine gluconate) and betadiene. This will maximize the ability of the wound to heal while minimizing the risk of infection.
It is another object of the present invention to use the nonwoven material as described above for the manufacture of an absorbent wound care product, preferably as a base sheet for the manufacture of a compostable absorbent wound care product.
Preferably the use according to the invention includes the addition of an antibacterial chemical impregnation to the nonwoven material during the manufacture of the absorbent wound care product.
In a preferred embodiment of the invention, the nonwoven material of the compostable absorbent wound care product is further processed by hydroentanglement. Undergoing this additional process enables a greater range of material functionality design. Such attributes as thickness, drape, softness, strength and aesthetic appearance can be modified to meet specific wound care requirements
The invention will now be illustrated by examples. These examples are not limiting the scope of the invention in any way. The invention includes also any other embodiments which are based on the same inventive concept.
Examples
All samples discussed below were conditioned at 23°C±2°C and relative humidity 50%±5% for 24 hours. Example 1
A 38-gsm product of the invention was compared in terms of stiffness to a commercial absorptive woundcare product of 27 gsm. Even though the product of invention was higher in basis weight, meaning that more material for absorption of wound exudate is present, the product of invention had 35% less overall stiffness, meaning it is much more comfortable to wear and offers a better fit to body surface.
Stiffness was measured using a 'Handle-o-meter', according to standard method WSP 90.3, with ¼ inch slot width, stainless steel surface, 1000 g beam. Sample size was to 10 x 10 cm.
Example 2
The 38 gsm product of invention of example 1 was tested for wicking (or spread ability) of liquid versus a commercial woundcare product of the same basis weight, comprised of cellulosic staple fiber. Horizontal spread of liquid is an important feature of woundcare products as otherwise local overloading of the woundcare product with wound exudate can occur, followed by leaking.
The test method was as follows. Samples were conditioned at 23°C±2°C and relative humidity 50%±5% for 24 hours. 0.5 ml of test liquid (water with 2g/L of Sulfacide brilliant green dye) was pipetted onto the sample using an
Eppendorf pipette. After 5 min a picture of the liquid spread was taken and software (lmageJ1.49v, National Institute of Health, USA) used to evaluate the area of the liquid spread.
The fabric of the invention achieved a 14% greater spread area than the commercial sample.

Claims

A nonwoven material for use in an absorbent wound care product, characterized in that it comprises at least one essentially pure cellulosic nonwoven web produced as essentially continuous filaments which are multibonded by merged filaments, hydrogen bonding and/or physical intermingling of filaments.
The nonwoven material of claim 1 where the cellulosic nonwoven web is made according to a lyocell process.
The nonwoven material of Claim 1 where the nonwoven web is hydroentangled.
The nonwoven material of claim 1 where the basis weight is between 50 and 300 grams per square meter.
The nonwoven material of Claim 1 , where a second cellulosic nonwoven web, which is formed of essentially continuous filaments, pulp fiber or staple fiber, is formed on top of the first cellulosic nonwoven web and subsequently both layers are hydroentangled together.
A nonwoven material according to claim 1 , wherein the number of layers is at least two, preferably between two and ten, with a further preferred range from 2 to 6.
The nonwoven material of Claim 6, where the layers are formed of essentially continuous filaments, pulp fiber or staple fiber, and subsequently all layers are bonded together using merged filament bonding, hydrogen bonding and filament intermingling.
The nonwoven material of Claim 6, where the layers are formed of essentially continuous filaments, pulp fiber or staple fiber, and subsequently all layers are hydroentangled together.
The nonwoven material of the preceding claims, where one or more of the cellulosic nonwoven layers within the nonwoven material, if formed of essentially continuous filaments, are made according to a lyocell process.
Use of a nonwoven material according to claim 1 for the manufacture of an absorbent wound care product.
11. Use according to claim 10, wherein the nonwoven material is used as a base sheet for the manufacture of a compostable absorbent wound care product.
12. Use according to claim 10 wherein the manufacture of an absorbent wound care product includes the addition of an antibacterial chemical impregnation to the nonwoven material.
13. An absorbent wound care product characterized in that it contains a nonwoven material according to claim 1 as a base sheet
14. An absorbent wound care product according to claim 13 which contains an antibacterial chemical impregnation to the nonwoven material.
PCT/AT2017/000031 2017-04-03 2017-04-03 A nonwoven web designed for use in a wound care product WO2018184050A1 (en)

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