Polyvinyl alcohol fibers and textile products

Abstract

A method for producing polyvinyl alcohol fiber, comprising the steps of: a homopolymer polyvinyl alcohol having a degree of hydrolysis of 88% to 98% or more and a weight average molecular weight in the range of 14,000 to 22,000; and a copolymer of diglycerol, triglycerol, fructose, ribose, xylose, D-mannitol, triacetin, pentaerythritol, dipentaerythritol, methylpentanediol, 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, 1. A method for producing a polyvinyl alcohol composition comprising: providing a polyvinyl alcohol composition comprising a plasticizer selected from the group consisting of ethanol, 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 propionic acid, and mixtures thereof; melting the composition at a temperature of 200°C to 230°C to form a molten polymer; extruding the molten composition to form an extrudate; forming the extrudate into a molten fiber; and solidifying the molten fiber to form a solid fiber.

Description

[Technical Field]

[0001] The present invention relates to polyvinyl alcohol fibers, methods of making polyvinyl alcohol fibers, and products made from polyvinyl alcohol fibers. The present invention particularly relates, but is not limited to, to products comprising nonwoven polyvinyl alcohol fibers, methods of making nonwoven polyvinyl alcohol fibers, and products incorporating such fibers. [Background technology]

[0002] Polyvinyl alcohol has many advantages over polymers traditionally used in the manufacture of nonwoven textiles: it dissolves in water, especially when heated, facilitating recovery, recycling, and environmental degradation.

[0003] Polyvinyl alcohol is produced by hydrolysis of homopolymers or copolymers of polyvinyl acetate. Polyvinyl alcohol produced by partial or complete hydrolysis of homopolymer polyvinyl acetate is called homopolymer polyvinyl alcohol. The degree of hydrolysis determines the properties of the resulting polymer. Copolymer polyvinyl alcohol or homopolymer polyvinyl alcohol with a low degree of hydrolysis (LD) is easy to process but has poor mechanical and chemical properties. Homopolymer polyvinyl alcohol with a high degree of hydrolysis (HD), for example, 85% or more, has excellent properties but cannot be processed without degradation under the conditions of equipment used to produce polyolefin nonwoven fibers.

[0004] Polyvinyl alcohol dissolves in water and fibers are conventionally made by solution spinning methods using polyvinyl alcohol with a low degree of hydrolysis (LD).

[0005] To improve water resistance, heat stretching, such as hot stretching, and chemical processes, such as acetylation, are required.

[0006] WO 2017 / 046361 discloses a method for producing processable polyvinyl alcohol having a degree of hydrolysis of 98% or more. WO 2022 / 008521 discloses a method for producing processable polyvinyl alcohol having a degree of hydrolysis ranging from 93% to 98% or more. WO 2022 / 008516 discloses a method for producing plasticized polyvinyl alcohol having a degree of hydrolysis of 93% to 98% or more. Summary of the Invention [Means for solving the problem]

[0007] According to a first aspect of the present invention, a method for producing polyvinyl alcohol fibers comprises the steps of: a homopolymer polyvinyl alcohol having a degree of hydrolysis of 88% to 98% or more and a weight average molecular weight in the range of 14,000 to 35,000; a plasticizer selected from the group consisting of diglycerol, triglycerol, fructose, ribose, xylose, D-mannitol, triacetin, pentaerythritol, dipentaerythritol, methylpentanediol, 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; an optional stabilizer selected from the group consisting of sodium stearate, potassium oleate, sodium benzoate, calcium stearate, stearic acid, dimethylpentanediol, propionic acid, and mixtures thereof; providing a polyvinyl alcohol composition comprising: melting the composition at a temperature of 190°C to 250°C to form a molten polymer; extruding the molten composition to form an extrudate; forming the extrudate into molten fibers; solidifying the molten fibers to form solid fibers; Includes:

[0008] The molten fibers may be drawn to form individual solid fibers or bundles of solid fibers.

[0009] Alternatively, the method may further comprise: forming the molten fibers into a molten or partially solidified nonwoven fibrous product; solidifying the product to form a solid nonwoven fibrous product; may include:

[0010] In embodiments, the degree of hydrolysis may range from 90 to 95%, preferably from 93 to 95%.

[0011] The molecular weight of the homopolymer polyvinyl alcohol can range from 14,000 to 35,000.

[0012] Molecular weights herein are weight average molecular weights and are determined using conventional liquid chromatography techniques.

[0013] The composition may be melted at a temperature of 220°C to 240°C.

[0014] The polyvinyl alcohol composition may have a melt flow index (MFI) of 30 to 80 g / 10 min, e.g., 50 to 75 g / 10 min, e.g., 70 to 75 g / 10 min. The melt flow index referred to herein is determined at 230°C using a 10 kg weight by conventional techniques.

[0015] The polyvinyl alcohol composition is preferably stable at the temperatures at which it is melted and extruded. Polyvinyl alcohols without the plasticizers and stabilizers disclosed herein, especially homopolymers with a high degree of hydrolysis, may tend to decompose at the temperatures required for melting and extrusion processing.

[0016] The advantageous polyvinyl alcohol fibers of the present invention can be processed on an industrial scale using conventional fiber processing equipment.

[0017] The polyvinyl alcohol of the present invention can be processed into filaments or fibers, which can be converted by crimping and cutting into stable fibers suitable for carding, wet laying, and air laying to form a variety of nonwoven products.

[0018] The polyvinyl alcohol fiber of the present invention can be spun at a speed of, for example, 4,500 m / min. -1 It is an advantage that it can be processed on an industrial scale using equipment operating at room temperature.

[0019] The stabilized polyvinyl alcohol polymers used in the present invention may be prepared in accordance with WO 2022 / 008516 and WO 2022 / 008521, the disclosures of which are incorporated herein by reference for all purposes.

[0020] The polyvinyl alcohol composition is introducing into a mixing reactor a polyvinyl alcohol polymer comprising a homopolymer polyvinyl alcohol or a blend thereof having a degree of hydrolysis ranging from 88% to 98% by weight or greater, The mixing reactor includes a blending chamber having a first inlet, a first outlet, and at least two interengaging components extending between the first inlet and the first outlet, the components configured to apply a shear force to the polymer while the polymer is conveyed by the components from the inlet through the reaction zone to the outlet; one or more second inlets located downstream of the first inlet for introducing reactants, including processing aids, plasticizers, and optional reaction stabilizers, into the chamber to form a reaction mixture; The plasticizer is selected from the group disclosed above, the reaction stabilizer, when present, is selected from the group consisting of sodium stearate, potassium oleate, sodium benzoate, calcium stearate, stearic acid, dimethylpropionic acid, and mixtures thereof; the blending chamber includes a plurality of heating zones configured to subject the mixture to a temperature profile in which the temperature increases from the inlet to the outlet; a second outlet located between the reaction zone and the first outlet configured to allow removal of a processing aid from the chamber; reacting the treating agent, plasticizer, and polymer in a reaction zone to form a plasticized polymer; passing the plasticized polymer through a first outlet; It can be made by a method comprising:

[0021] The use of a reactive mixing device, typically an extruder according to the present invention, allows the processing aids and plasticizers to react with the polyvinyl alcohol or blends thereof without decomposing the polymer, followed by removal of all or most of the processing aids through a second outlet to obtain the plasticized polyvinyl alcohol or blends thereof.

[0022] The use of a reactive stabilizer can advantageously reduce the degree of degradation during melt processing. This allows homopolymer polyvinyl alcohols with a high degree of hydrolysis, for example, 88% by weight or more, to be processed to form fibers or pellets (from which fibers can be formed by extrusion). The reactive stabilizer can be used in an amount of about 0.1% to about 5% by weight, for example, about 0.1% to about 3% by weight, for example, 0.1% to about 1.5% by weight, for example, about 0.2% to about 0.5% by weight, for example, about 0.25% by weight.

[0023] The reactive stabilizers of the present invention can reduce the degree of polymer degradation during processing. Homopolymer polyvinyl alcohol has been difficult to process due to its decomposition at the required high temperatures. This susceptibility to degradation has led to the use of polyvinyl alcohol copolymers with consequently reduced 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.

[0024] The use of homopolymer polyvinyl alcohol is particularly advantageous. Homopolymer polyvinyl alcohol is produced by hydrolysis of homopolymer polyvinyl acetate, and the degree of hydrolysis is 90% by weight or more in an embodiment of the present invention. Polyvinyl alcohol copolymers produced by hydrolysis of polyvinyl acetate copolymers have inferior properties compared to homopolymer polyvinyl alcohol. Homopolymer polyvinyl alcohol can exhibit advantageous properties.

[0025] The homopolymer polyvinyl alcohol polymer fibers of the present invention can have high tensile strength and flexibility compared to previously available polyvinyl alcohol fibers.

[0026] Polyvinyl alcohol may be produced by hydrolysis of the homopolymer polyvinyl acetate, the degree of hydrolysis being in the range of from 88% to 98% by weight, for example from 90% to 95% by weight.

[0027] A blend of two or more polyvinyl alcohol polymers may be used, for example, a blend of two polyvinyl alcohol polymers having a relatively high molecular weight and a relatively low molecular weight, respectively.

[0028] Blends of polyvinyl alcohols having the same molecular weight and different degrees of hydrolysis can be combined. Mixing different polyvinyl alcohol grades together can improve the properties of the resulting polymer, such as melt strength.

[0029] For fiber production, a blend of two polyvinyl alcohol polymers having molecular weights in the range of 22,000 to 38,000, the first polymer having a low degree of hydrolysis and the second polymer having a high degree of hydrolysis, can be mixed in a ratio of 40:60 to 60:40 by weight, for example about 50:50.

[0030] The blend of polymers of different molecular weights used is selected depending on the physical properties required in the final product. These may require the use of materials of different molecular weights. The use of three or more polymers of different molecular weights may be advantageous. The use of a single molecular weight polymer is not excluded.

[0031] The use of a blend can allow for control of the viscosity of the polymer. The selection of a stabilizer according to the present invention allows for the use of a blend with a desired viscosity without compromising other properties. Alternatively, the use of a blend can allow for the use of polyvinyl alcohol containing one or more stabilizers while maintaining viscosity or other properties to allow for pellet or film production.

[0032] The processing aid is preferably water. Alternatively, the processing aid may comprise a mixture of water and one or more hydroxyl compounds having a boiling point lower than the boiling point or melting point of the plasticizer. For cost and environmental reasons, the use of water is preferred. Two or more plasticizers may be used. When a mixture of plasticizers is used, a two-component mixture may be preferred.

[0033] In one embodiment, the plasticizer 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.

[0034] The total amount of plasticizer in the formulation can be from about 15% to about 30% by weight.

[0035] The polymer compositions and fibers of the present invention may be free of, or free of significant amounts of, water-soluble salts, oils, waxes, or ethylene homopolymers or copolymers.

[0036] The method of the present invention offers many advantages. The method allows for the formation of heat-processable polyvinyl alcohol, which can be used to produce highly functional, economical fibers while eliminating plastic pollution. Polyvinyl alcohol is water-soluble, environmentally harmless, and inherently biodegradable. Hydrophilic polymers, such as polyvinyl alcohol, degrade environmentally faster than hydrophobic polymers and do not exhibit bioaccumulation. Thermoplastic polyvinyl alcohol can be mechanically recycled and pelletized for repeated use.

[0037] The fibers of the present invention may exhibit advantageous chemical resistance, particularly to alcohols, acids and alkalis.

[0038] The fibers of the present invention may have advantageously smaller diameters than previously available polyvinyl alcohol fibers. Fibers with smaller diameters have a larger surface area, which may be advantageous for air filtration, for example, in face masks. Finer fibers may also have a softer texture. Furthermore, finer fibers may also have an increased rate of biodegradation after use.

[0039] According to a second aspect of the present invention there is provided a heat-treatable polyvinyl alcohol fibre made according to the first aspect of the present invention. According to a third aspect of the present invention there is provided a heat-treatable nonwoven fibrous product comprising fibres made according to the method of the first aspect of the present invention.

[0040] The heat-processable polyvinyl alcohol of the present invention can be formed into fibers by a variety of methods.

[0041] Filament extrusion can be used to form monofilament and multifilament fibers.

[0042] Spunbonding processes can be used to form nonwoven fabrics. Meltblown processes can be used to form nonwoven fabrics.

[0043] A nonwoven product is defined by ISO 9092 as an engineered fibrous assembly, primarily planar, that is given a desired level of structural integrity by physical and / or chemical means, excluding woven, knitted or paper-made fabrics.

[0044] The homopolymer polyvinyl alcohol fibers of the present invention offer many advantages over previously available polyvinyl alcohol-containing fibers. The fibers of the present invention and products made from these fibers exhibit improved tensile strength, barrier properties, water solubility, and biodegradability. Homopolymer polyvinyl alcohol fibers can unexpectedly exhibit all of these properties. In comparison, copolymers have only been able to provide one or more of these properties at the expense of others, impairing one or more of these properties. The fibers and products of the present invention have a desirable monomaterial structure that does not suffer from these drawbacks.

[0045] Nonwoven products comprising the polyvinyl alcohol fibers of the present invention in combination with fibers of cellulose pulp, viscose, and mixtures thereof have excellent flushability, for example, in accordance with UK Water Fine to Flush WIZ 4-02-06. Wet wipes made from the nonwoven fibers of the present invention exhibit excellent dry and wet tensile strength.

[0046] The fibers of the present invention can be produced by extruding filaments of molten polyvinyl alcohol polymer through a spinneret with small holes, for example, 0.25 mm in diameter. The extruded filaments can be drawn using heated rollers, sometimes called godet rollers, which rotate at various speeds to form multifilament tows. The multifilament tows can be crimped by heating, subsequently shaped by toothed or grooved rollers, and cut by rotating blades to provide fibers of the desired length. The use of specific fiber lengths can provide compatibility with various nonwoven fiber processing techniques.

[0047] The following extrusion and stretching conditions may be used:

[0048] Extrusion temperatures of 200°C to 247°C, preferably 210°C to 220°C, can be used. Within these ranges, higher extrusion temperatures can be used to process polymers with higher degrees of hydrolysis. The number of filaments in the fiber can range from 24 to 72. The use of fibers or yarns containing a larger number of filament bundles can be advantageous to increase the overall diameter of the filament bundle during drawing, improving its bonding, and can also allow for the use of higher draw ratios. A larger number of filaments allows the tension applied during the drawing process to be distributed among a larger number of filaments.

[0049] The rotational speed of the first godet roller (godet 1) may be 200 to 400 mpm (m / min). Using godet 1 speeds above 400 mpm may increase the frequency of melt breakage. The optimum speed for godet 1 may be approximately 391 mpm. The rotational speed of the godet 5 roller may be 350 to 1665 mpm. The rotational speeds of godets 2 to 4 may have intermediate values. Higher draw ratios may be achieved using 72 filaments, resulting in finer fibers of 3 dtex or more at godet 5 speeds of 500 rpm or higher.

[0050] A spin finish can be applied to the filaments before the fibers move to the godet roller. Non-aqueous spin finish oils such as Tallopol DT, Tallopon Biocone, or Vystat can be used. Spin finish contents of 0.4% to 4.7% by weight can be used with spin finish pump speeds of 4 to 15 rpm.

[0051] A minimum of 0.4% by weight of spin finish may be used to provide sufficient inter-filament bonding for drawing and winding. The fibers of the present invention may be intertwined to form a nonwoven layer or web by a variety of methods, including carding, air laying, or wet laying. The fibers in the web may be bonded by a method selected from hydroentanglement, needle punching, chemical or adhesive bonding, and thermal bonding.

[0052] In the carding process, fiber bundles are separated and individualized using carding wires to produce an oriented fiber network. Crimped polyvinyl alcohol fibers can be used.

[0053] The use of the heat-treatable fibers of the present invention allows for industrial-scale production of textile products consisting of or including homopolymer polyvinyl alcohol. Blends of polyvinyl alcohol (PVOH) fibers with sustainable fibers can be used, for example, the sustainable fibers can be biopolymers such as lyocell, polylactic acid (PLA), and mixtures thereof. A variety of fibers can be used.

[0054] A PVOH:Lyocell blend ratio of 70:30% to 90:10% by weight, preferably 80:20% by weight, or a PVOH:PLA ratio of 70:30% to 90:10% by weight, preferably 80:20% by weight, can be used.

[0055] Carded web: 60-40 gm -2 , for example, about 50gm -2 The surface density may be

[0056] In one embodiment, 100% PVOH and 80:20 wt% PVOH:Lyocell carded webs can be needle punched to a penetration depth of 9 mm and hydroentangled at 30 bar or chemically bonded using, for example, an ethylene vinyl acetate (EVA) binder.

[0057] For example, through-air bonding, in which hot air is passed through the web by convection, can be used to melt the adhesive to avoid excessive compression.

[0058] In one embodiment, an 80:20 wt % PVOH:PLA carded web may be through-air bonded at 120° C. for 2 minutes.

[0059] An air-laying method may be used which uses turbulent air flow to create an isotropic fiber network.

[0060] In one embodiment, crimped polyvinyl alcohol fibers can be cut to lengths of 5 mm and mixed with pulp fibers (approximately 2 mm), such as Georgia Pacific (GP) cellulose.

[0061] A ratio of polyvinyl alcohol:cellulose of 80:20% to 20:80% by weight, for example about 50:50% by weight, may be used.

[0062] Areal density is approximately 50 gm depending on the application, e.g., single or multiple use applications. -2 It could be.

[0063] The airlaid web can be hydroentangled and then dried.

[0064] The fibers of the present invention offer the advantage that polyvinyl alcohol fiber-containing webs can be converted into hydroentangled airlaid nonwoven fabrics having high strength. In particular, it has been found that fibers containing warm water-soluble polyvinyl alcohol partially dissolve during the hydroentanglement process, producing a strong, yet stiff, fabric.

[0065] To form nonwoven fabrics containing hot, water-soluble polyvinyl alcohol fibers, a wet-laying process can be used, in which the polyvinyl alcohol fibers are dispersed in water and transferred to a foraminous conveying device through which the water is removed to deposit a web of fibers.

[0066] In an embodiment, the fibers may be cut to a suitable length, for example, 5 mm, and mixed with pulp fibers, for example, Sodra Black, in a ratio of 50:50 wt. % to 20:80 wt. % polyvinyl alcohol:pulp.

[0067] Lyocell fibers (1.4 dtex / 5 mm) can be mixed with polyvinyl alcohol:pulp in a ratio of 50:50 wt% to 20:80 wt%.

[0068] The surface density is approximately 60gm -2 This density can be used to make flushable wipes.

[0069] The wet laid web can be hydroentangled and dried at 100°C for 30 seconds.

[0070] The tensile strength can be compared with commercially available products: a blend of polyvinyl alcohol:pulp:lyocell in a ratio of 40:40:20% by weight can exhibit a relatively high tensile strength of 11-13N, typically about 12N.

[0071] The hydroentangled wet-laid fabrics of the present invention incorporating pulp have relatively good tensile strength. Pulp fibers typically have high liquid absorption capacity. After hydroentanglement, the wet-laid web remains saturated, resulting in partial dissolution of the polyvinyl alcohol fibers during the drying stage. The polyvinyl alcohol fibers act as a binder along with the hydrogen bonds formed between the pulp fibers.

[0072] Increasing the specific energy during hydroentanglement can increase the dry tensile strength of fabrics incorporating lyocell fibers.

[0073] Percentages and other amounts referred to herein are by weight unless otherwise specified and are selected from any range to add up to 100%. [Brief explanation of the drawings]

[0074] The invention will now be further illustrated by way of example and not by way of limitation with reference to the accompanying drawings, in which: [Figure 1] 1 is a diagrammatic view of a fiber extrusion apparatus according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0075] In embodiments of the present invention, the following polyvinyl alcohol homopolymer compositions may be used:

[0076] Polymer Composition A PVOH; degree of hydrolysis 98%; low viscosity 35.97% PVOH; degree of hydrolysis 89%; low viscosity 35.97% Trimethylolpropane 14.37% Sodium benzoate 0.21% Glycerol 4.29% Water 9.20%

[0077] Polymer Composition B PVOH; Hydrolysis degree 99%; High viscosity 7.193% PVOH; degree of hydrolysis 98%; low viscosity 64.737% Trimethylolpropane 14.37% Sodium benzoate 0.21 Glycerol 4.29% Water 9.20%

[0078] Polymer Composition C PVOH; degree of hydrolysis 98%; low viscosity 35.87% PVOH; degree of hydrolysis 89%; low viscosity 35.87% Dipentaerythritol 6.21% Triacetin 12.41% Sodium benzoate 0.25% Water 9.39%

[0079] Polymer Composition D PVOH; degree of hydrolysis 98%; low viscosity 22.61% PVOH; degree of hydrolysis 97%; intermediate viscosity 52.76% Dipentaerythritol 4.99% Sodium benzoate 0.25% Triacetin 10.00% Water 9.39%

[0080] 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%

[0081] 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% Methylpentanediol 5.50% Glycerol 4.50%

[0082] Polymer Composition G PVOH; degree of hydrolysis 98%; low viscosity 72.45% PVOH; Hydrolysis degree 99%; High viscosity 9.20% Dipentaerythritol 7.95% Methylpentanediol 5.63% Glycerol 4.50% Sodium benzoate 0.27%

[0083] FIG. 1 shows an apparatus for extruding polyvinyl alcohol fibers according to the present invention. A feed hopper (1) supplies pellets of a polyvinyl alcohol composition to an extruder (2). Molten polymer is delivered from the extruder to a melt pump (3), which meters the polymer to a spin pack (4). The spin pack spins the fibers (10) through a quench chamber (5) supplied with cooling air by a fan (11). A spin finish applicator (6) applies a coating to the fibers (10). The fibers are then delivered by rollers (7) to a series of godet rollers (8), which produce drawn fibers. The fibers are then collected in a winder (9). [Example]

[0084] Example 1 Multifilament polyvinyl alcohol fibers were extruded using the following parameters:

[0085] [Table 1] JPEG2025526175000003.jpg53170

[0086] The fibre was crimped using an IR heater temperature of 220°C, a speed of 1.4 m / min, an indent roller temperature of 100°C and a throughput rate of 17 g / h.

[0087] The results show that the compound can be drawn to a higher ratio to form finer fibers with a thickness of 2 dtex. Higher melt strength was achieved.

[0088] The following properties were observed using polyvinyl alcohol (PVOH), lyocell, and polylactic acid (PLA).

[0089] [Table 2]

[0090] The properties of the airlaid hydroentangled polyvinyl alcohol (PVOH) web were as follows:

[0091] [Table 3]

[0092] The properties of the wet laid hydroentangled PVOH web were as follows:

[0093] [Table 4]

[0094] In a further embodiment, the properties of the wet-laid hydroentangled PVOH web were as follows:

[0095] [Table 5]

[0096] Example 2 The tensile strength of the webs containing the polyvinyl alcohol / pulp blend was compared to that of commercially available flushable wipes.

[0097] The tensile strength was compared to that of wipes saturated with lotion. The commercially available wipes were squeezed by hand to remove excess lotion. The excess lotion was used to saturated the polyvinyl alcohol product of the present invention at a pick-up rate of 200-300% by weight.

[0098] Wet-laid webs hydroentangled at high specific energy (30 bar x 2 / bar x 4) exhibited higher wet tensile strength compared to the benchmark flushable wipes and wet-laid webs hydroentangled at low specific energy (30 bar x 2 / 50 bar x 2). Increasing specific energy had a positive impact on the wet tensile strength of the wet-laid hydroentangled fabrics, with increases of approximately 100-170%.

[0099] There was no significant difference in wet strength between 50:50 polyvinyl alcohol:lyocell and 80:20 polyvinyl alcohol:lyocell fabrics hydroentangled at high specific energy (p>0.05).

[0100] Example 3 The dispersibility of polyvinyl alcohol / pulp blends in wastewater was compared with that of commercially available flushable wipes.

[0101] Tests were conducted to determine sewer dispersibility. Commercial wipes exhibited poor dispersibility, with less than 60% passing through a 5.6 mm sieve.

[0102] Polyvinyl alcohol wetlaid fabrics hydroentangled at low specific energy (30 bar x 2 / 50 bar x 2) showed relatively good dispersibility, with >70 wt% passing through a 5.6 mm sieve. Reducing the lyocell fiber length from 5 mm to 3 mm had a positive effect on dispersibility.

[0103] The dispersibility of the wet-laid hydroentangled fabric decreased with increasing specific energy (30 bar x 2 / 50 bar x 4). The fibers were more intertwined with each other, which promoted fiber roping.

[0104] After dispersibility testing, the wet-laid webs hydroentangled at high specific energy showed a fragment size of <4 cm, which is one of the alternative requirements for passing sewer dispersibility.

[0105] Polyvinyl alcohol fibers were successfully converted into wet-laid, hydroentangled fabrics. Fabrics incorporating pulp fibers exhibited good dry and wet tensile strength and dispersibility, while the incorporation of lyocell fibers promoted wet tensile strength but reduced dispersibility in the hydroentangled, wet-laid fabrics.

[0106] Commercially available flushable wipes passed the drainage test for dispersibility, with more than 50% by weight passing through a 12.5 mm sieve.

[0107] Wet-laid hydroentangled polyvinyl alcohol-containing webs showed excellent results, with over 80% by weight passing through a 12.5 mm sieve.

[0108] Example 4 A hydroentangled wet-laid nonwoven polyvinyl alcohol / pulp fabric was compared to commercially available flushable wipes.

[0109] Commercially available flushable wipes showed poor dispersibility, with less than 60% by weight passing through a 5.6 mm sieve. A hydroentangled wetlaid fabric incorporating 20% by weight polyvinyl alcohol fiber and 80% by weight pulp showed excellent results, with 90% by weight passing through a 5.6 mm sieve.

[0110] Webs containing polyvinyl alcohol, pulp and viscose / lyocell showed better dispersibility performance compared to commercially available flushable wipes.

[0111] The use of polyvinyl alcohol fibers in hydroentangled wet-laid fabrics incorporating pulp fibers improved dry tensile strength. The incorporation of viscose or lyocell fibers improved the wet strength of the fabric. An excellent combination of wet strength and dispersibility performance was achieved using 40% by weight polyvinyl alcohol, 40% by weight pulp, and 20% by weight viscose fibers.

Claims

1. 1. A method for producing polyvinyl alcohol fibers, comprising: a homopolymer polyvinyl alcohol having a degree of hydrolysis of 88% to 98% by weight or more and a weight average molecular weight in the range of 14,000 to 35,000; a plasticizer selected from the group consisting of diglycerol, triglycerol, fructose, ribose, xylose, D-mannitol, triacetin, pentaerythritol, dipentaerythritol, methylpentanediol, 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; an optional stabilizer selected from the group consisting of sodium stearate, potassium oleate, sodium benzoate, calcium stearate, stearic acid, dimethylpentanediol, propionic acid, and mixtures thereof; providing a polyvinyl alcohol composition comprising: melting the composition at a temperature of 190°C to 250°C to form a molten polymer; extruding the molten composition to form an extrudate; forming the extrudate into molten fibers; solidifying the molten fibers to form solid fibers; A method comprising:

2. 2. The method of claim 1, wherein the degree of hydrolysis is from 90% to 98% by weight.

3. 3. The method of claim 2, wherein the degree of hydrolysis is from 95% to 98% by weight.

4. The method according to any one of claims 1 to 3, wherein the melt flow index of the polyvinyl alcohol composition is in the range of 30 to 80.

5. The method according to any one of claims 1 to 4, wherein the melt flow index of the polyvinyl alcohol composition is in the range of 50 to 75.

6. The method of any one of claims 1 to 5, wherein the melt flow index of the polyvinyl alcohol composition is in the range of 70 to 75.

7. 7. The method of any one of claims 1 to 6, wherein the plasticizer is selected from two or more of the group consisting of diglycerol, triglycerol, xylose, D-mannitol, triacetin, dipentaerythritol, 1,4-butanediol, 3,3-dimethyl-1,2-butanediol, and caprolactam.

8. The method of any one of claims 1 to 7, wherein the polymer composition is a blend of two or more polyvinyl alcohol homopolymers having the same degree of hydrolysis and different molecular weights.

9. Polyvinyl alcohol fibers produced according to any one of claims 1 to 8.

10. A nonwoven fibrous product produced according to the method of any one of claims 1 to 8.

11. 11. The nonwoven fibrous product of claim 10, which is a disposable wipe.

12. A nonwoven fiber comprising a homopolymer polyvinyl alcohol having a degree of hydrolysis of 88% by weight or greater.

13. A nonwoven fibrous product comprising a homopolymer polyvinyl alcohol having a degree of hydrolysis of 88% by weight or greater.

14. 14. The nonwoven fibrous product of claim 13, which is a disposable wipe.

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