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EP4321667A1 - Polyvinyl alcohol fibres and meltblown fibrous products - Google Patents

Polyvinyl alcohol fibres and meltblown fibrous products Download PDF

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Publication number
EP4321667A1
EP4321667A1 EP23191163.7A EP23191163A EP4321667A1 EP 4321667 A1 EP4321667 A1 EP 4321667A1 EP 23191163 A EP23191163 A EP 23191163A EP 4321667 A1 EP4321667 A1 EP 4321667A1
Authority
EP
European Patent Office
Prior art keywords
polyvinyl alcohol
fibres
range
hydrolysis
degree
Prior art date
Legal status (The legal status 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 status listed.)
Pending
Application number
EP23191163.7A
Other languages
German (de)
French (fr)
Inventor
John Williams
Sian Griffiths
Robert Ashworth
Jack EATON
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Aquapak IP Ltd
Original Assignee
Aquapak IP Ltd
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 Aquapak IP Ltd filed Critical Aquapak IP Ltd
Publication of EP4321667A1 publication Critical patent/EP4321667A1/en
Pending legal-status Critical Current

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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
    • D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
    • D04H3/08—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating
    • D04H3/16—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating with bonds between thermoplastic filaments produced in association with filament formation, e.g. immediately following extrusion
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/08—Melt spinning methods
    • D01D5/098—Melt spinning methods with simultaneous stretching
    • D01D5/0985—Melt spinning methods with simultaneous stretching by means of a flowing gas (e.g. melt-blowing)
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F1/00—General methods for the manufacture of artificial filaments or the like
    • D01F1/02—Addition of substances to the spinning solution or to the melt
    • D01F1/10—Other agents for modifying properties
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D01F6/14—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of unsaturated alcohols, e.g. polyvinyl alcohol, or of their acetals or ketals
    • 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
    • D04H1/54—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 by welding together the fibres, e.g. by partially melting or dissolving
    • D04H1/56—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 by welding together the fibres, e.g. by partially melting or dissolving in association with fibre formation, e.g. immediately following extrusion of staple fibres
    • 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
    • D04H3/005—Synthetic yarns or filaments
    • D04H3/007—Addition polymers

Definitions

  • This invention relates to polyvinyl alcohol fibres, methods of making polyvinyl alcohol fibres and products manufactured from polyvinyl alcohol fibres.
  • the invention relates particularly but not exclusively to products comprising meltblown polyvinyl alcohol fibres, methods of making meltblown polyvinyl alcohol fibres and products incorporating such fibres.
  • Polyvinyl alcohol has many advantages in comparison to polymers which are traditionally used for manufacture of non-woven fibre products. Polyvinyl alcohol is soluble in water, particularly when heated, facilitating reclamation, recycling and environmental degradation.
  • Polyvinyl alcohol is manufactured by hydrolysis of homopolymer or co-polymers of polyvinyl acetate.
  • Polyvinyl alcohol manufactured by partial or complete hydrolysis of homopolymeric polyvinyl acetate is referred to as homopolymeric polyvinyl alcohol.
  • the degree of hydrolysis determines the properties of the resultant polymer.
  • Co-polymeric polyvinyl alcohols or homopolymeric polyvinyl alcohol with a low degree (LD) of hydrolysis are easy to process but have inferior mechanical and chemical properties.
  • Homopolymeric polyvinyl alcohol with a high degree (HD) of hydrolysis, for example 85% or greater, has superior properties but is not processable without degradation under conditions using apparatus employed for manufacture of polyolefin non-woven fibres.
  • Polyvinyl alcohol is soluble in water and fibres have traditionally been made by solution spinning methods using polyvinyl alcohol with a low degree (LD) of hydrolysis.
  • WO2017/046361 discloses a method for manufacture of processable polyvinyl alcohol having a degree of hydrolysis of 98% or greater.
  • WO2022/008521 discloses a method for manufacture of processable polyvinyl alcohol having a degree of hydrolysis in the range of 93% to 98% or more.
  • WO2022/008516 discloses a method for manufacture of plasticised polyvinyl alcohol having a degree of hydrolysis of 93% to 98% or more.
  • a method of manufacture of a nonwoven product comprising polyvinyl alcohol fibres comprises the steps of:
  • Melt blowing is a one step process which transforms a melt-processable polymer, particularly polyvinyl alcohol compositions of this invention into non-woven fabric.
  • Pellets of the polymer may be melted and the melt forced by spin pumps through spinnerets containing multiple small orifices.
  • the extruded polymer strands are attenuated just after the die using streams of hot air.
  • the attenuated filaments are subsequently laid down on a collector to form a melt blown web, thus forming a self-bonded melt blown web composed of fine filaments of the polyvinyl alcohol composition.
  • Melt blown non-woven fabrics are characterised as having very fine filaments, typically in the range 1 to 5 ⁇ m.
  • the degree of hydrolysis may be 90-95%, preferably 93-95%.
  • the molecular weight of the homopolymeric polyvinyl alcohol may be in the range from 14,000 to 22,000, for example, 15,000 to 20,000, for example 16,000 to 20,000.
  • Molecular weights in this specification are weight average molecular weights and are measured using conventional liquid chromatographic techniques.
  • the composition may be melted at a temperature from 220°C to 240°C.
  • the polyvinyl alcohol composition of this invention may have a melt flow index (MFI) of 30 to 80g/10min, for example 50 to 75g/10min, for example 70 to 75g/10min.
  • Melt flow indices referred to in this specification are determined at 230°C using a weight of 10kg by conventional techniques.
  • the polyvinyl alcohol composition of this invention is stable at the temperature at which it is melted and extruded.
  • Polyvinyl alcohol, not containing a plasticiser and stabiliser as disclosed herein, particularly the homopolymer having a high degree of hydrolysis, may be liable to decompose at the temperatures required for melting and extrusion processing.
  • Advantageous polyvinyl alcohol fibres of this invention are capable of being processed on a commercial scale, using conventional meltblowing apparatus.
  • the stabilised polyvinyl alcohol polymers used in this invention may be manufactured in accordance with WO2022/008516 and WO2022/008521 , the disclosures of which are incorporated into this specification by reference for all purposes.
  • the polyvinyl alcohol composition may be made by a method comprising the steps of:
  • a reactive mixing apparatus typically an extruder in accordance with this invention allows the processing aid and plasticiser to be reacted with the polyvinyl alcohol or blend thereof, without decomposition of the polymer followed by removal of all or most of the processing aid from the secondary outlet to give plasticised polyvinyl alcohol or a blend thereof.
  • a reactive stabiliser may result in an advantageous reduction in the extent of degradation during melt processing. This allows homopolymeric polyvinyl alcohol having a high degree of hydrolysis, for example 88 wt% or higher to be processed to form fibres or pellets from which fibres may be formed by extrusion.
  • the reactive stabiliser may be used in an amount of about 0.1 wt% to about 5 wt%, for example about 0.1 wt% to about 3 wt%, for example 0.1 wt% to about 1.5 wt%, for example from about 0.2 wt% to about 0.5 wt%, for example about 0.25 wt%.
  • the reactive stabilisers of this invention may decrease the extent of degradation of the polymer during processing.
  • Homopolymeric polyvinyl alcohol has been difficult to process due to degradation at the high temperatures required.
  • the liability of degradation has led to use of polyvinyl alcohol co-polymers with a consequent loss of engineering properties. This can be seen by UV spectral analysis of the amount of conjugation present in the polymer. Sodium benzoate has been found to be particularly effective.
  • homopolymeric polyvinyl alcohol is particularly advantageous.
  • Homopolymeric polyvinyl alcohol is manufactured by hydrolysis of homopolymeric polyvinyl acetate, the degree of hydrolysis being 90wt% or more in embodiments of this invention.
  • Polyvinyl alcohol co-polymers made by hydrolysis of polyvinyl acetate co-polymers have inferior properties compared to homopolymeric polyvinyl alcohol.
  • Homopolymeric polyvinyl alcohol may exhibit advantageous properties.
  • Polyvinyl alcohol polymers of this invention may have high tensile strength and flexibility.
  • the polyvinyl alcohol may be manufactured by hydrolysis of homopolymeric polyvinyl acetate, wherein the extent of hydrolysis is in the range from 88 wt% up to 98 wt%, for example 90 wt% to less than 95 wt%.
  • a blend of two or more polyvinyl alcohol polymers may be employed, for example a blend of two polyvinyl alcohol polymers with a relatively high molecular weight and a relatively low molecular weight respectively.
  • a blend of polyvinyl alcohols with the same molecular weight and different degrees of hydrolysis can be combined. Blending different polyvinyl alcohol grades together enables the properties of the resultant polymer to be enhanced, for example melt strength.
  • a blend of two polyvinyl alcohol polymers with a molecular weight in the range 14,000 to 22,000 a first polymer having a low degree of hydrolysis and a second polymer having a high degree of hydrolysis may be blended in a ratio of 40:60 to 60:40, for example about 50:50 by weight.
  • the blends of different molecular weight polymers employed are selected in accordance with the physical properties required in the finished product. This may require different molecular weight materials being used. Use of more than two different molecular weight polymers may be advantageous. The use of a single molecular weight polymer is not precluded.
  • a blend may allow control of the viscosity of the polymer. Selection of a stabiliser in accordance with the present invention allows use of blends of a desired viscosity without a loss of other properties. Alternatively, use of a blend may permit use of polyvinyl alcohol with one or more stabilisers while maintaining viscosity or other properties to permit manufacture of pellets or films.
  • the processing aid is preferably water.
  • the processing aid may comprise a mixture of water and one or more hydroxyl compound with a boiling point less than the boiling point or melting point of the plasticiser. Use of water is preferred for cost and environmental reasons.
  • Two or more plasticisers may be employed.
  • a binary mixture may be preferred.
  • the plasticiser may be selected from the group consisting of: diglycerol, triglycerol, xylose, D-mannitol, triacetin, dipentaerythritol, 1,4-butanediol, 3,3-dimethyl-1,2-butanediol, and caprolactam.
  • the total amount of plasticiser in the formulation may be from about 15 wt% to about 30 wt%.
  • Polymer compositions and fibres of the present invention may not include any or any substantial amount of a water soluble salt, oil, wax or ethylene homopolymer or copolymer.
  • the method of this invention provides many advantages.
  • the method allows formation of thermally processable polyvinyl alcohol which can be used to create economical fibres that are highly functional while eliminating plastic pollution.
  • Polyvinyl alcohol is water-soluble, non-toxic to the environment and inherently biodegradable.
  • Hydrophilic polymers for example, polyvinyl alcohol degrade environmentally faster than hydrophobic polymers and do not show bioaccumulation.
  • Thermoplastic polyvinyl alcohol can be mechanically recycled into pellets for repeated use.
  • Homopolymeric polyvinyl alcohol fibres of this invention provide many advantages in comparison to previously available polyvinyl alcohol containing fibres.
  • the fibres of this invention and products made from these fibres exhibit improved tensile strength, barrier properties, water solubility and biodegradability.
  • Homopolymeric polyvinyl alcohol fibres may unexpectedly exhibit all of these properties.
  • copolymers have only been able to compromise and provide one or more of these properties at the expense of other properties.
  • the fibres and products of the present invention have a desirable monomaterial structure which does not suffer from this disadvantage.
  • the fibres of this invention may exhibit advantageous chemical resistance, particularly to alcohols, acids and alkalis.
  • Meltblown fibres of this invention may have an advantageous smaller diameter. Fibres having a smaller diameter have a greater surface area which may be advantageous for air filtration, for example in face masks. Finer fibres may also be softer in texture. Furthermore, finer fibres may also have an increased rate of biodegradation after use.
  • meltblown homopolymeric polyvinyl alcohol fibre having a degree of hydrolysis of 88 wt% to 98 wt% or greater.
  • the fibre may be manufactured in accordance with the first aspect of the present invention.
  • a meltblown non-woven fibre product comprising fibres of homopolymeric polyvinyl alcohol having a degree of hydrolysis of 88 wt% to 98 wt% or greater.
  • the product may be made in accordance with the method of the first aspect of the present invention.
  • a non-woven product is defined by ISO9092 as an engineered fibrous assembly, primarily planar, which has been given a designed level of structural integrity by physical and/or chemical means, excluding weaving, knitting or paper making.
  • the areal density may be about 50gm -2 , dependent on the application, for example single or multiple use applications.
  • the areal density may be about 60gm -2 .
  • Non woven fabrics having this density may be employed for manufacture of flushable wipes.
  • the die temperature may be in the range 200°C to 230°C.
  • An optimal die temperature may be 220°C. Melt breaks may be observed at higher temperatures.
  • the air flow volume may be in the range 2,000 to 7,000 1 min -1 , for example 5,900 to 6,900 1 min -1 .
  • a higher air flow of 7,000 1 min -1 may allow greater drawing of the polymer stream and may allow the average filament diameter to be reduced from 14.1 ⁇ m to 12.6 ⁇ m.
  • the die air temperature may be in the range 200 to 280°C, for example 245 to 280°C.
  • a preferred air temperature may be 220 to 240°C.
  • An increase to a higher die air temperature may result in more frequent melt breaks.
  • a die-to-collector distance of 0.1 to 0.25m, for example 0.24m may be employed.
  • Meltblown polyvinyl alcohol nonwoven fabrics of this invention find many applications which utilise the unique properties of homopolymeric polyvinyl alcohol.
  • polyvinyl alcohol (PVOH) homopolymer compositions may be employed.
  • PVOH degree of hydrolysis 98%; low viscosity 25.20% PVOH; degree of hydrolysis 98%; low viscosity 5.20% PVOH; degree of hydrolysis 89%; low viscosity 25.21% Dipentaerythritol 5.00% Triacetin 10.00% Water 9.39%
  • FIGS 1 and 2 illustrate meltblowing apparatus used in accordance with the present invention.
  • An extruder (1) supplies molten polyvinyl alcohol composition to a gear pump (2) which feeds the polymer to a die (3).
  • Air manifolds (4) supply primary high velocity air flows to the die outlet (5) so that the primary air flows surround the die outlet (6) of the polymer feed (7).
  • the primary air flows create a stream of molten fibres (8) directed towards a rotating cylindrical collector (9).
  • Secondary air flows (10) serve the cool the streams of molten polymer fibres, promoting solidification of the polymer streams as they contact the collector (9) to form a solidified non-woven web (11).
  • the solidified web (11) is drawn from the collector and wound upon a rotary winder (12).
  • An advantageous polyvinyl alcohol polymer for formation of melt blown fabrics had a degree of hydrolysis of 94%, using trimethylolpropane as a plasticiser with additional glycerol.
  • the resultant meltblown fabrics had an areal density of 60.88g/m 2 , thickness of 0.51mm; filament diameter of 12.61 ⁇ m; air impermeability at 200 Pa of 3,536 l.min -2 s -1 and tensile strength, MD of 0.44 l/25mm, before thermal bonding.
  • a significant proportion (65%) of the filament diameters was measured between 5 and 14 ⁇ m with an average filament diameter of 12.6 ⁇ m.
  • the air velocity was 6,900 l.min -1 at an air flow of 6,200 l.min -1
  • a significant proportion of the filament diameters was between 10 and 14 ⁇ m with an average filament diameter of 14.12 ⁇ m. Higher air velocity allowed attenuation of the polymers into fine filaments.

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  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Artificial Filaments (AREA)
  • Nonwoven Fabrics (AREA)

Abstract

A method of manufacture of a nonwoven product comprising polyvinyl alcohol fibres, the method comprises the steps of:providing a polyvinyl alcohol composition comprising homopolymeric polyvinyl alcohol having a degree of hydrolysis of 88% to 98% or greater; and a weight average molecular weight in the range from 14,000 to 22,000;a plasticiser selected from the group consisting of: diglycerol, triglycerol, fructose, ribose, xylose, D-mannitol, triacetin, pentaerythritol, dipentaerythritol, methyl pentanediol, 1,2-propanediol, 1,4-butanediol, 2-hydroxy-1,3-propanediol, 3-methyl-1,3-butanediol, 3,3-dimethyl-1,2-butanediol, polyethylene glycol 300, polyethylene glycol 400, alkoxylated polyethylene glycol, caprolactam, tricyclic trimethylolpropane formal, rosin esters, erucamide, and mixtures thereof; andan optional stabilizer selected from the group consisting of: sodium stearate, potassium oleate, sodium benzoate, calcium stearate, stearic acid, dimethyl pentane diol, propionic acid and mixtures thereof;melting the composition at a temperature from 200°C to 230°C to form a molten polymer;wherein the molten polymer is meltblown by the steps of:extrusion of the molten polymer through a die having a spinneret to form molten fibres of the polymer;the fibres being blown from the die and attenuated by a flow of heated air to form attenuated molten fibres, the attenuated fibres being deposited on a moving collector and allowed to solidify to form a melt blown nonwoven fibre web.

Description

  • This invention relates to polyvinyl alcohol fibres, methods of making polyvinyl alcohol fibres and products manufactured from polyvinyl alcohol fibres. The invention relates particularly but not exclusively to products comprising meltblown polyvinyl alcohol fibres, methods of making meltblown polyvinyl alcohol fibres and products incorporating such fibres.
  • Polyvinyl alcohol has many advantages in comparison to polymers which are traditionally used for manufacture of non-woven fibre products. Polyvinyl alcohol is soluble in water, particularly when heated, facilitating reclamation, recycling and environmental degradation.
  • Polyvinyl alcohol is manufactured by hydrolysis of homopolymer or co-polymers of polyvinyl acetate. Polyvinyl alcohol manufactured by partial or complete hydrolysis of homopolymeric polyvinyl acetate is referred to as homopolymeric polyvinyl alcohol. The degree of hydrolysis determines the properties of the resultant polymer. Co-polymeric polyvinyl alcohols or homopolymeric polyvinyl alcohol with a low degree (LD) of hydrolysis are easy to process but have inferior mechanical and chemical properties. Homopolymeric polyvinyl alcohol with a high degree (HD) of hydrolysis, for example 85% or greater, has superior properties but is not processable without degradation under conditions using apparatus employed for manufacture of polyolefin non-woven fibres.
  • Polyvinyl alcohol is soluble in water and fibres have traditionally been made by solution spinning methods using polyvinyl alcohol with a low degree (LD) of hydrolysis.
  • In order to enhance water resistance, thermal e.g. hot drawing and chemical e.g. acetylation steps have been required.
  • WO2017/046361 discloses a method for manufacture of processable polyvinyl alcohol having a degree of hydrolysis of 98% or greater.
  • WO2022/008521 discloses a method for manufacture of processable polyvinyl alcohol having a degree of hydrolysis in the range of 93% to 98% or more.
  • WO2022/008516 discloses a method for manufacture of plasticised polyvinyl alcohol having a degree of hydrolysis of 93% to 98% or more.
  • According to a first aspect of the present invention, a method of manufacture of a nonwoven product comprising polyvinyl alcohol fibres, the method comprises the steps of:
    • providing a polyvinyl alcohol composition comprising homopolymeric polyvinyl alcohol having a degree of hydrolysis of 88% to 98% or greater; and a weight average molecular weight in the range from 14,000 to 35,000;
    • a plasticiser selected from the group consisting of: diglycerol, triglycerol, fructose, ribose, xylose, D-mannitol, triacetin, pentaerythritol, dipentaerythritol, methyl pentanediol, 1,2-propanediol, 1,4-butanediol, 2-hydroxy-1,3-propanediol, 3-methyl-1,3-butanediol, 3,3-dimethyl-1,2-butanediol, polyethylene glycol 300, polyethylene glycol 400, alkoxylated polyethylene glycol, caprolactam, tricyclic trimethylolpropane formal, rosin esters, erucamide, and mixtures thereof; and
    • an optional stabilizer selected from the group consisting of: sodium stearate, potassium oleate, sodium benzoate, calcium stearate, stearic acid, dimethyl pentane diol, propionic acid and mixtures thereof;
    • melting the composition at a temperature from 190°C to 240°C to form a molten polymer;
    • wherein the molten polymer is meltblown by the steps of:
      • extrusion of the molten polymer through a die having a spinneret to form molten fibres of the polymer;
      • the fibres being blown from the die and attenuated by a flow of heated air to form attenuated molten fibres, the attenuated fibres being deposited on a moving collector and allowed to solidify to form a melt blown nonwoven fibre web.
  • Melt blowing is a one step process which transforms a melt-processable polymer, particularly polyvinyl alcohol compositions of this invention into non-woven fabric. Pellets of the polymer may be melted and the melt forced by spin pumps through spinnerets containing multiple small orifices. The extruded polymer strands are attenuated just after the die using streams of hot air. The attenuated filaments are subsequently laid down on a collector to form a melt blown web, thus forming a self-bonded melt blown web composed of fine filaments of the polyvinyl alcohol composition. Melt blown non-woven fabrics are characterised as having very fine filaments, typically in the range 1 to 5µm.
  • For meltblown applications, the degree of hydrolysis may be 90-95%, preferably 93-95%.
  • For meltblown applications, the molecular weight of the homopolymeric polyvinyl alcohol may be in the range from 14,000 to 22,000, for example, 15,000 to 20,000, for example 16,000 to 20,000.
  • Molecular weights in this specification are weight average molecular weights and are measured using conventional liquid chromatographic techniques.
  • In embodiments, the composition may be melted at a temperature from 220°C to 240°C.
  • The polyvinyl alcohol composition of this invention may have a melt flow index (MFI) of 30 to 80g/10min, for example 50 to 75g/10min, for example 70 to 75g/10min. Melt flow indices referred to in this specification are determined at 230°C using a weight of 10kg by conventional techniques.
  • The polyvinyl alcohol composition of this invention is stable at the temperature at which it is melted and extruded. Polyvinyl alcohol, not containing a plasticiser and stabiliser as disclosed herein, particularly the homopolymer having a high degree of hydrolysis, may be liable to decompose at the temperatures required for melting and extrusion processing.
  • Advantageous polyvinyl alcohol fibres of this invention are capable of being processed on a commercial scale, using conventional meltblowing apparatus.
  • The stabilised polyvinyl alcohol polymers used in this invention may be manufactured in accordance with WO2022/008516 and WO2022/008521 , the disclosures of which are incorporated into this specification by reference for all purposes.
  • The polyvinyl alcohol composition may be made by a method comprising the steps of:
    • introducing into a mixing reactor a polyvinyl alcohol polymer comprising homopolymeric polyvinyl alcohol or a blend thereof having a degree of hydrolysis in the range of 88 wt% to 98 wt% or more;
    • wherein the mixing reactor comprises a blending chamber having a primary inlet, a primary outlet and at least two inter-engaging components extending between the primary inlet and primary outlet, the components being arranged to apply a shearing force to the polymer while the polymer is conveyed by the components from the inlet through a reaction zone to the outlet;
    • one or more secondary inlets located downstream from the primary inlet for introducing reactants comprising a processing aid, a plasticiser and an optional reactive stabiliser to the chamber to form a reaction mixture;
    • wherein the plasticiser is selected from the group disclosed above;
    • wherein the reactive stabiliser when present is selected from the group consisting of:
      sodium stearate, potassium oleate, sodium benzoate, calcium stearate, stearic acid, dimethyl propionic acid, and mixtures thereof;
    • wherein the blending chamber comprises a plurality of heated regions arranged so that the mixture is subjected to a temperature profile whereby the temperature increases from the inlet to the outlet;
    • a secondary outlet located between the reaction zone and primary outlet arranged to allow removal of processing aid from the chamber;
    • reacting the processing agent, plasticiser and polymer in the reaction zone to form plasticised polymer; and
    • allowing the plasticised polymer to pass from the primary outlet.
  • Use of a reactive mixing apparatus, typically an extruder in accordance with this invention allows the processing aid and plasticiser to be reacted with the polyvinyl alcohol or blend thereof, without decomposition of the polymer followed by removal of all or most of the processing aid from the secondary outlet to give plasticised polyvinyl alcohol or a blend thereof.
  • Use of a reactive stabiliser may result in an advantageous reduction in the extent of degradation during melt processing. This allows homopolymeric polyvinyl alcohol having a high degree of hydrolysis, for example 88 wt% or higher to be processed to form fibres or pellets from which fibres may be formed by extrusion.
  • The reactive stabiliser may be used in an amount of about 0.1 wt% to about 5 wt%, for example about 0.1 wt% to about 3 wt%, for example 0.1 wt% to about 1.5 wt%, for example from about 0.2 wt% to about 0.5 wt%, for example about 0.25 wt%.
  • The reactive stabilisers of this invention may decrease the extent of degradation of the polymer during processing. Homopolymeric polyvinyl alcohol has been difficult to process due to degradation at the high temperatures required. The liability of degradation has led to use of polyvinyl alcohol co-polymers with a consequent loss of engineering properties. This can be seen by UV spectral analysis of the amount of conjugation present in the polymer. Sodium benzoate has been found to be particularly effective.
  • Use of homopolymeric polyvinyl alcohol is particularly advantageous. Homopolymeric polyvinyl alcohol is manufactured by hydrolysis of homopolymeric polyvinyl acetate, the degree of hydrolysis being 90wt% or more in embodiments of this invention. Polyvinyl alcohol co-polymers made by hydrolysis of polyvinyl acetate co-polymers have inferior properties compared to homopolymeric polyvinyl alcohol. Homopolymeric polyvinyl alcohol may exhibit advantageous properties.
  • Polyvinyl alcohol polymers of this invention may have high tensile strength and flexibility.
  • The polyvinyl alcohol may be manufactured by hydrolysis of homopolymeric polyvinyl acetate, wherein the extent of hydrolysis is in the range from 88 wt% up to 98 wt%, for example 90 wt% to less than 95 wt%.
  • A blend of two or more polyvinyl alcohol polymers may be employed, for example a blend of two polyvinyl alcohol polymers with a relatively high molecular weight and a relatively low molecular weight respectively.
  • A blend of polyvinyl alcohols with the same molecular weight and different degrees of hydrolysis can be combined. Blending different polyvinyl alcohol grades together enables the properties of the resultant polymer to be enhanced, for example melt strength.
  • For fibre production a blend of two polyvinyl alcohol polymers with a molecular weight in the range 14,000 to 22,000, a first polymer having a low degree of hydrolysis and a second polymer having a high degree of hydrolysis may be blended in a ratio of 40:60 to 60:40, for example about 50:50 by weight.
  • The blends of different molecular weight polymers employed are selected in accordance with the physical properties required in the finished product. This may require different molecular weight materials being used. Use of more than two different molecular weight polymers may be advantageous. The use of a single molecular weight polymer is not precluded.
  • Use of a blend may allow control of the viscosity of the polymer. Selection of a stabiliser in accordance with the present invention allows use of blends of a desired viscosity without a loss of other properties. Alternatively, use of a blend may permit use of polyvinyl alcohol with one or more stabilisers while maintaining viscosity or other properties to permit manufacture of pellets or films.
  • The processing aid is preferably water. Alternatively, the processing aid may comprise a mixture of water and one or more hydroxyl compound with a boiling point less than the boiling point or melting point of the plasticiser. Use of water is preferred for cost and environmental reasons.
  • Two or more plasticisers may be employed.
  • When a mixture of plasticisers is employed, a binary mixture may be preferred.
  • In an embodiment, the plasticiser may be selected from the group consisting of: diglycerol, triglycerol, xylose, D-mannitol, triacetin, dipentaerythritol, 1,4-butanediol, 3,3-dimethyl-1,2-butanediol, and caprolactam.
  • The total amount of plasticiser in the formulation may be from about 15 wt% to about 30 wt%.
  • Polymer compositions and fibres of the present invention may not include any or any substantial amount of a water soluble salt, oil, wax or ethylene homopolymer or copolymer.
  • The method of this invention provides many advantages. The method allows formation of thermally processable polyvinyl alcohol which can be used to create economical fibres that are highly functional while eliminating plastic pollution. Polyvinyl alcohol is water-soluble, non-toxic to the environment and inherently biodegradable. Hydrophilic polymers, for example, polyvinyl alcohol degrade environmentally faster than hydrophobic polymers and do not show bioaccumulation. Thermoplastic polyvinyl alcohol can be mechanically recycled into pellets for repeated use.
  • Homopolymeric polyvinyl alcohol fibres of this invention provide many advantages in comparison to previously available polyvinyl alcohol containing fibres. The fibres of this invention and products made from these fibres exhibit improved tensile strength, barrier properties, water solubility and biodegradability. Homopolymeric polyvinyl alcohol fibres may unexpectedly exhibit all of these properties. In comparison, copolymers have only been able to compromise and provide one or more of these properties at the expense of other properties. The fibres and products of the present invention have a desirable monomaterial structure which does not suffer from this disadvantage.
  • The fibres of this invention may exhibit advantageous chemical resistance, particularly to alcohols, acids and alkalis.
  • Meltblown fibres of this invention may have an advantageous smaller diameter. Fibres having a smaller diameter have a greater surface area which may be advantageous for air filtration, for example in face masks. Finer fibres may also be softer in texture. Furthermore, finer fibres may also have an increased rate of biodegradation after use.
  • According to a second aspect of the present invention there is provided meltblown homopolymeric polyvinyl alcohol fibre having a degree of hydrolysis of 88 wt% to 98 wt% or greater. The fibre may be manufactured in accordance with the first aspect of the present invention.
  • According to a third aspect of the present invention, there is provided a meltblown non-woven fibre product comprising fibres of homopolymeric polyvinyl alcohol having a degree of hydrolysis of 88 wt% to 98 wt% or greater. The product may be made in accordance with the method of the first aspect of the present invention.
  • A non-woven product is defined by ISO9092 as an engineered fibrous assembly, primarily planar, which has been given a designed level of structural integrity by physical and/or chemical means, excluding weaving, knitting or paper making.
  • The areal density may be about 50gm-2, dependent on the application, for example single or multiple use applications.
  • In embodiments, the areal density may be about 60gm-2. Non woven fabrics having this density may be employed for manufacture of flushable wipes.
  • The following processing parameters may be employed.
  • The die temperature may be in the range 200°C to 230°C. An optimal die temperature may be 220°C. Melt breaks may be observed at higher temperatures.
  • The air flow volume may be in the range 2,000 to 7,000 1 min-1, for example 5,900 to 6,900 1 min-1. A higher air flow of 7,000 1 min-1 may allow greater drawing of the polymer stream and may allow the average filament diameter to be reduced from 14.1µm to 12.6µm.
  • The die air temperature may be in the range 200 to 280°C, for example 245 to 280°C. A preferred air temperature may be 220 to 240°C. An increase to a higher die air temperature may result in more frequent melt breaks. A die-to-collector distance of 0.1 to 0.25m, for example 0.24m may be employed.
  • Meltblown polyvinyl alcohol nonwoven fabrics of this invention find many applications which utilise the unique properties of homopolymeric polyvinyl alcohol.
  • Percentages and other quantities referred to in this specification are by weight unless stated otherwise and are selected from any ranges quoted to total 100%.
  • The invention is further described by means of example but not in any limitative sense, with reference to the accompanying drawings, of which:
    • Figure 1 is a diagrammatic view of meltblowing apparatus in accordance with this invention; and
    • Figure 2 is a cross sectional view of the die of the apparatus shown in Figure 1.
  • In embodiments of the present invention the following polyvinyl alcohol (PVOH) homopolymer compositions may be employed.
    • Polymer composition A
  • PVOH; degree of hydrolysis 98%; low viscosity 35.97%
    PVOH; degree of hydrolysis 89%; low viscosity 35.97%
    Trimethylol propane 14.37%
    Sodium benzoate 0.21%
    Glycerol 4.29%
    Water 9.20%
    • Polymer composition B
  • PVOH; degree of hydrolysis 99%; high viscosity 7.193%
    PVOH; degree of hydrolysis 98%; low viscosity 64.737%
    Trimethylol propane 14.37%
    Sodium benzoate 0.21
    Glycerol 4.29%
    Water 9.20%
    • Polymer composition C
  • PVOH; degree of hydrolysis 98%; low viscosity 35.87%
    PVOH; degree of hydrolysis 89%; low viscosity 35.87%
    Di-pentaerythritol 6.21%
    Triacetin 12.41%
    Sodium benzoate 0.25%
    Water 9.39%
    • Polymer composition D
  • PVOH; degree of hydrolysis 98%; low viscosity 22.61%
    PVOH; degree of hydrolysis 97%; medium viscosity 52.76%
    Dipentaerythritol 4.99%
    Sodium benzoate 0.25%
    Triacetin 10.00%
    Water 9.39%
    • Polymer composition E
  • PVOH; degree of hydrolysis 98%; low viscosity 25.20%
    PVOH; degree of hydrolysis 98%; low viscosity 5.20%
    PVOH; degree of hydrolysis 89%; low viscosity 25.21%
    Dipentaerythritol 5.00%
    Triacetin 10.00%
    Water 9.39%
    • Polymer composition F
  • PVOH; degree of hydrolysis 98%; low viscosity 27.33%
    PVOH; degree of hydrolysis 98%; low viscosity 27.33%
    PVOH; degree of hydrolysis 89%; low viscosity 27.33%
    Dipentaerythritol 8.00%
    Methyl pentanediol 5.50%
    Glycerol 4.50%
    • Polymer composition G
  • PVOH; degree of hydrolysis 98%; low viscosity 72.45%
    PVOH; degree of hydrolysis 99%; high viscosity 9.20%
    Dipentaerythritol 7.95%
    Methyl pentanediol 5.63%
    Glycerol 4.50%
    Sodium benzoate 0.27%
  • Figures 1 and 2 illustrate meltblowing apparatus used in accordance with the present invention.
  • An extruder (1) supplies molten polyvinyl alcohol composition to a gear pump (2) which feeds the polymer to a die (3). Air manifolds (4) supply primary high velocity air flows to the die outlet (5) so that the primary air flows surround the die outlet (6) of the polymer feed (7). The primary air flows create a stream of molten fibres (8) directed towards a rotating cylindrical collector (9). Secondary air flows (10) serve the cool the streams of molten polymer fibres, promoting solidification of the polymer streams as they contact the collector (9) to form a solidified non-woven web (11). The solidified web (11) is drawn from the collector and wound upon a rotary winder (12).
    • Example 1
  • Meltblown polyvinyl alcohol fibres were extruded using the following parameters.
  • Meltblowing of a polyvinyl alcohol composition of this invention was carried out using the following parameters. Polymer composition A was employed.
    • Meltblowing parameters
  • Parameters
    Extruding zone
    1 180°C
    Extruding zone
    2 200°C
    Extruding zone
    3 205°C
    Die temperature 210-220°C
    Air temperature 240-280°C
    Air flow volume 6900 1.min-1
    Die-to-collector distance 0.1-0.3m
    Extrusion speed 6-16rpm
    Die hole diameter 0.25mm
    Air angle 45°
    Air knife gap 0.7-1.4mm
  • An advantageous polyvinyl alcohol polymer for formation of melt blown fabrics had a degree of hydrolysis of 94%, using trimethylolpropane as a plasticiser with additional glycerol.
  • The resultant meltblown fabrics had an areal density of 60.88g/m2, thickness of 0.51mm; filament diameter of 12.61µm; air impermeability at 200 Pa of 3,536 l.min-2 s-1 and tensile strength, MD of 0.44 l/25mm, before thermal bonding.
  • A significant proportion (65%) of the filament diameters was measured between 5 and 14µm with an average filament diameter of 12.6µm. The air velocity was 6,900 l.min-1 at an air flow of 6,200 l.min-1, a significant proportion of the filament diameters was between 10 and 14µm with an average filament diameter of 14.12µm. Higher air velocity allowed attenuation of the polymers into fine filaments.

Claims (19)

  1. A method of manufacture of a nonwoven product comprising polyvinyl alcohol fibres, the method comprising the steps of:
    providing a polyvinyl alcohol composition comprising homopolymeric polyvinyl alcohol having a degree of hydrolysis of 88% to 98% or greater; and a weight average molecular weight in the range from 14,000 to 35,000;
    a plasticiser selected from the group consisting of: diglycerol, triglycerol, fructose, ribose, xylose, D-mannitol, triacetin, pentaerythritol, dipentaerythritol, methyl pentanediol, 1,2-propanediol, 1,4-butanediol, 2-hydroxy-1,3-propanediol, 3-methyl-1,3-butanediol, 3,3-dimethyl-1,2-butanediol, polyethylene glycol 300, polyethylene glycol 400, alkoxylated polyethylene glycol, caprolactam, tricyclic trimethylolpropane formal, rosin esters, erucamide, and mixtures thereof; and
    an optional stabilizer selected from the group consisting of: sodium stearate, potassium oleate, sodium benzoate, calcium stearate, stearic acid, dimethyl pentane diol, propionic acid and mixtures thereof;
    melting the composition at a temperature from 190°C to 240°C to form a molten polymer;
    wherein the molten polymer is meltblown by the steps of:
    extrusion of the molten polymer through a die having a spinneret to form molten fibres of the polymer;
    the fibres being blown from the die and attenuated by a flow of heated air to form attenuated molten fibres, the attenuated fibres being deposited on a moving collector and allowed to solidify to form a melt blown nonwoven fibre web.
  2. A method as claimed in claim 1, wherein the degree of hydrolysis is 90 to 95%.
  3. A method as claimed in claim 2, wherein the degree of hydrolysis is 93 to 95%.
  4. A method as claimed in any preceding claim, wherein the molecular weight of the homopolymeric polyvinyl alcohol is in the range of 14,000 to 22,000.
  5. A method as claimed in claim 4, wherein the molecular weight of the homopolymeric polyvinyl alcohol is in the range of 15,000 to 20,000.
  6. A method as claimed in claim 5, wherein the molecular weight of the homopolymeric polyvinyl alcohol is in the range of 16,000 to 20,000.
  7. A method as claimed in claim 6, wherein the composition is melted at a temperature in the range from 220°C to 230°C.
  8. A method as claimed in any preceding claim, wherein the polyvinyl alcohol composition has a melt flow index in the range of 30 to 80g/10min.
  9. A method as claimed in claim 8, wherein the polyvinyl alcohol composition has a melt flow index in the range of 50 to 75g/10min.
  10. A method as claimed in claim 9, wherein the polyvinyl alcohol composition has a melt flow index in the range of 70 to 75g/10min.
  11. A method as claimed in any preceding claim, wherein the molten polymer is extruded from a die having a temperature in the range of 200°C to 220°C.
  12. A method as claimed in any preceding claim, wherein the air temperature at the die is in the range of 200°C to 280°C.
  13. A method as claimed in any preceding claim, wherein the air pressure at the die is 50 kPa to 110 kPa.
  14. A method as claimed in any preceding claim, wherein the fibre diameter is in the range of 12 µm to 15 µm.
  15. A meltblown polyvinyl alcohol fibre made in accordance with any preceding claim.
  16. A meltblown nonwoven fabric comprising homopolymeric polyvinyl alcohol having a degree of hydrolysis of 88 wt% to 98 wt% or greater.
  17. A meltblown nonwoven fabric consisting of homopolymeric polyvinyl alcohol having a degree of hydrolysis of 88 wt% to 98 wt% or greater.
  18. A meltblown nonwoven homopolymeric polyvinyl alcohol fabric made by the method of any of claims 1 to 14.
  19. A product incorporating a meltblown fabric as claimed in any of claims 16 to 18, wherein the product is selected from the group consisting of: dry wipes, hygiene top sheets and core wraps, filters, face masks and personal protective equipment.
EP23191163.7A 2022-08-13 2023-08-11 Polyvinyl alcohol fibres and meltblown fibrous products Pending EP4321667A1 (en)

Applications Claiming Priority (1)

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EP22190328.9A EP4321664A1 (en) 2022-08-13 2022-08-13 Polyvinyl alcohol fibres and meltblown fibrous products

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Citations (7)

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Publication number Priority date Publication date Assignee Title
US5445785A (en) * 1991-12-19 1995-08-29 Kimberly-Clark Corporation Method of preparing a nonwoven web of poly(vinyl alcohol) fibers
JP2000314067A (en) * 1999-02-24 2000-11-14 Kuraray Co Ltd Thermoplastic polyvinylalcohol-based melt blown non- woven fabric and its production
JP2001123369A (en) * 1999-10-20 2001-05-08 Kuraray Co Ltd Hydrolyzable nowoven fabric and method for producing the same
US20030216098A1 (en) * 2002-02-19 2003-11-20 Thomas Carlyle Dissolvable polyvinyl alcohol nonwoven
WO2017046361A1 (en) 2015-09-18 2017-03-23 Aquapak Polymers Limited Process and apparatus for manufacture of processable polyvinyl alcohol
US20170369693A1 (en) * 2013-03-25 2017-12-28 Peter Morris Research And Development Limited Water-soluble polymer and polymer internal lubricant
WO2022008521A1 (en) 2020-07-06 2022-01-13 Aquapak Polymers Limited Process for manufacture of plasticised homopolymeric polyvinyl alcohol and plasticised polyvinyl alcohol polymer obtained therefrom

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4132804A1 (en) * 1991-04-10 1992-10-15 Isolyser Co Disposable garments and articles soluble in hot water
WO2021262929A1 (en) * 2020-06-27 2021-12-30 Monosol, Llc Film-enclosed formed bath experience products and method of manufacture

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5445785A (en) * 1991-12-19 1995-08-29 Kimberly-Clark Corporation Method of preparing a nonwoven web of poly(vinyl alcohol) fibers
JP2000314067A (en) * 1999-02-24 2000-11-14 Kuraray Co Ltd Thermoplastic polyvinylalcohol-based melt blown non- woven fabric and its production
JP2001123369A (en) * 1999-10-20 2001-05-08 Kuraray Co Ltd Hydrolyzable nowoven fabric and method for producing the same
US20030216098A1 (en) * 2002-02-19 2003-11-20 Thomas Carlyle Dissolvable polyvinyl alcohol nonwoven
US20170369693A1 (en) * 2013-03-25 2017-12-28 Peter Morris Research And Development Limited Water-soluble polymer and polymer internal lubricant
WO2017046361A1 (en) 2015-09-18 2017-03-23 Aquapak Polymers Limited Process and apparatus for manufacture of processable polyvinyl alcohol
WO2022008521A1 (en) 2020-07-06 2022-01-13 Aquapak Polymers Limited Process for manufacture of plasticised homopolymeric polyvinyl alcohol and plasticised polyvinyl alcohol polymer obtained therefrom
WO2022008516A1 (en) 2020-07-06 2022-01-13 Aquapak Polymers Limited Method for manufacture of a plasticised polyvinyl alcohol mixture

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