Extruded polyvinyl alcohol fibers and textile products

Abstract

1. A method for producing a nonwoven product comprising polyvinyl alcohol fibers, the method comprising the step of: mixing a homopolymer polyvinyl alcohol having a degree of hydrolysis of 88% to 98% or more and a molecular weight in the range of 22,000 to 38,000 with 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 glycols, caprolactam, tricyclic 1. A method for producing a polyvinyl alcohol composition comprising: providing a polyvinyl alcohol composition comprising a plasticizer selected from the group consisting of trimethylolpropane formal, rosin ester, erucamide, and mixtures thereof; and a stabilizer selected from the group consisting of sodium stearate, potassium oleate, sodium benzoate, calcium stearate, stearic acid, dimethylpentanediol, propionic acid, and mixtures thereof; melting the composition at a temperature of 190°C to 250°C; extruding the molten composition to form an extrudate; forming the extrudate into molten fibers; drawing the molten fibers to form individual molten fibers or bundles of molten fibers; and solidifying the molten fibers to form solid fibers or bundles of solid fibers.

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 extruded polyvinyl alcohol fibers, methods of making extruded 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 by weight. 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% by weight or more and a weight average molecular weight in the range of 14,000 to 36,000; 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; a 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; extruding the molten composition to form an extrudate; forming the extrudate into molten fibers; drawing the molten fibers to form individual molten fibers or bundles of molten fibers; solidifying the molten fibers to form a solid fiber or bundle of solid fibers; Includes:

[0008] The degree of hydrolysis may be from 95% to 98% by weight, for example from 93% to 95% by weight.

[0009] In embodiments, the molecular weight of the homopolymer polyvinyl alcohol may range from 14,000 to 35,000.

[0010] Molecular weights herein are weight average molecular weights and are determined using conventional liquid chromatography techniques.

[0011] In embodiments, the composition may be melted at a temperature of 220°C to 240°C, e.g., 220°C to 230°C. The polyvinyl alcohol composition of the present invention 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.

[0012] The polyvinyl alcohol composition of the present invention is 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.

[0013] The advantageous polyvinyl alcohol fibers of the present invention can be processed on an industrial scale using conventional fiber processing equipment.

[0014] The polyvinyl alcohol of the present invention can be processed into filaments or fibers, which can be converted by crimping and cutting into staple fibers suitable for carding, wet laying, and air laying to form a variety of nonwoven products.

[0015] The advantageous polyvinyl alcohol fibers of the present invention have a fiber length of, for example, 4,500 m.min. -1 It is possible to process it on an industrial scale using equipment operating at 1000kJ / cm2.

[0016] 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.

[0017] The polyvinyl alcohol composition 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 reaction stabilizers, into the chamber to form a reaction mixture; The plasticizer is selected from the group disclosed above, the reaction stabilizer 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:

[0018] 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.

[0019] The use of reactive stabilizers can result in an advantageous reduction in the degree of degradation during melt processing, allowing homopolymer polyvinyl alcohols with high degrees of hydrolysis, for example, 88% by weight or greater, to be processed to form fibers or pellets from which fibers can be formed by extrusion.

[0020] The reaction stabilizer may be used in an amount of about 0.1% by weight to about 5% by weight, for example, about 0.1% by weight to about 3% by weight, for example, 0.1% by weight to about 1.5% by weight, for example, about 0.2% by weight to about 0.5% by weight, for example, about 0.25% by weight.

[0021] 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.

[0022] The use of homopolymer polyvinyl alcohol is particularly advantageous.

[0023] Homopolymer polyvinyl alcohol is produced by hydrolysis of homopolymer polyvinyl acetate, the degree of hydrolysis being 93% by weight or more in embodiments of the present invention. Polyvinyl alcohol copolymers made by hydrolysis of polyvinyl acetate copolymers have inferior properties compared to homopolymer polyvinyl alcohol.

[0024] Homopolymer polyvinyl alcohol can exhibit advantageous properties.

[0025] The polyvinyl alcohol polymers of the present invention can have high tensile strength and flexibility.

[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, such as from 93% to less than 98% by weight, for example from 93% to 97% by weight, for example from 93% 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 for the final product. This 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 below the boiling point or melting point of the plasticizer. For cost and environmental reasons, the use of water is preferred.

[0033] More than one plasticizer may be used.

[0034] When mixtures of plasticizers are used, two-component mixtures may be preferred.

[0035] 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.

[0036] The total amount of plasticizer in the formulation can be from about 15% to about 30% by weight.

[0037] 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.

[0038] 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.

[0039] The fibers of the present invention may have an advantageously smaller diameter. Fibers with a smaller diameter have a larger surface area, which may be advantageous for air filtration, for example, in face masks. The finer the fibers, the softer the texture may be. Furthermore, the finer the fibers, the faster the rate of biodegradation after use.

[0040] According to a second aspect of the present invention, there is provided a nonwoven product comprising heat-processable homopolymer polyvinyl alcohol fibres having a degree of hydrolysis of 88% by weight or greater, made according to the first aspect of the present invention.

[0041] According to a third aspect of the present invention, there is provided a nonwoven fibrous product comprising homopolymer polyvinyl alcohol fibres having a degree of hydrolysis of 88% by weight or greater.

[0042] A nonwoven product is defined by ISO 9092 as an engineered fibrous assembly, primarily planar, given a desired level of structural integrity by physical and / or chemical means, excluding woven, knitted or paper-made fabrics.

[0043] 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.

[0044] 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.

[0045] 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 godet rollers that 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.

[0046] The following extrusion and stretching conditions may be used:

[0047] Extrusion temperatures of 200°C to 250°C, preferably 210°C to 247°C, can be used.

[0048] The number of filaments in a fiber can range from 24 to 72, depending on the equipment used. The use of fibers containing bundles of 50 to 72 filaments can be advantageous for improving filament bundle bonding during drawing, allowing for 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 310 mpm (m / min). Using a godet 1 speed above 300 mpm may increase the frequency of melt breakage. The optimum speed for godet 1 may be approximately 295 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 metering pump speed can be used. The use of a metering pump can improve process stability. The reduced residence time can reduce the risk of thermal degradation of the polymer.

[0051] 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.

[0052] A minimum of 0.4% by weight of spin finish may be used to provide sufficient bonding between the filaments for drawing and winding.

[0053] 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.

[0054] 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.

[0055] The opened polyvinyl alcohol fibers may be dried, for example, at 130° C. for 10 minutes before carding to improve the uniformity of the resulting web. In an exemplary embodiment, drying is not necessary.

[0056] The use of the heat treatable fibers of the present invention allows for industrial scale production.

[0057] Blends of polyvinyl alcohol (PVOH) fibers with sustainable fibers may be used, for example, the sustainable fibers may be lyocell, polylactic acid (PLA), polyhydroxyalkanoates, and mixtures thereof.

[0058] A polyvinyl alcohol:lyocell blend ratio of 70:30% to 90:10% by weight, preferably 80:20% by weight, or a polyvinyl alcohol:PLA ratio of 70:30% to 90:10% by weight, preferably 80:20% by weight, can be used.

[0059] Carded web: 60-40 gm -2 , for example, about 50gm -2 The surface density may be

[0060] In one embodiment, 100% polyvinyl alcohol and 80:20% by weight polyvinyl alcohol:lyocell carded webs are needle punched to a penetration depth of 9 mm and hydroentangled at 30 bar or may be chemically bonded using, for example, an ethylene vinyl acetate (EVA) binder.

[0061] 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.

[0062] An 80:20 wt% polyvinyl alcohol:PLA carded web can be through-air bonded at 120°C for 2 minutes.

[0063] An air-laying method may be used which uses turbulent air flow to create an isotropic fiber network.

[0064] In one embodiment, crimped polyvinyl alcohol fibers can be cut to lengths of 5 mm and mixed with pulp fibers (approximately 2 mm), Georgia Pacific (GP) cellulose.

[0065] A ratio of polyvinyl alcohol:cellulose of 80:20% to 20:80% by weight, for example about 50:50% by weight, may be used.

[0066] Areal density is approximately 50 gm depending on the application, e.g., single or multiple use applications. -2 It could be.

[0067] The polyvinyl alcohol fibers may be dried, for example, at 130° C. for 10 minutes to improve separation. In an exemplary embodiment, drying is not necessary.

[0068] The airlaid web can be hydroentangled and then dried.

[0069] The fibers of the present invention have 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.

[0070] 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.

[0071] 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.

[0072] 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%.

[0073] The surface density is approximately 60gm -2 This density can be used to make flushable wipes.

[0074] The wet laid web can be hydroentangled and dried at 100°C for 30 seconds.

[0075] The tensile strength was compared with that of commercially available products. A blend of polyvinyl alcohol:pulp:lyocell in a ratio of 40:40:20% by weight showed a relatively high tensile strength of 11-13N, typically around 12N.

[0076] 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 in conjunction with the hydrogen bonds formed between the pulp fibers.

[0077] Increasing the specific energy during hydroentanglement can increase the dry tensile strength of fabrics incorporating lyocell fibers.

[0078] 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]

[0079] 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

[0080] In embodiments of the present invention, the following polyvinyl alcohol homopolymer compositions may be used:

[0081] 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%

[0082] Polymer Composition B PVOH; degree of hydrolysis 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%

[0083] 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%

[0084] 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%

[0085] 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%

[0086] 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%

[0087] 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%

[0088] 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]

[0089] Example 1 Multifilament polyvinyl alcohol fibers were extruded using the following parameters:

[0090] [Table 1]

[0091] 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.

[0092] The following properties were observed with polyvinyl alcohol (PVOH) and polylactic acid (PLA).

[0093] [Table 2]

[0094] The properties of the airlaid hydroentangled PVOH web were as follows:

[0095] [Table 3]

[0096] The properties of the wet laid hydroentangled PVOH web were as follows:

[0097] [Table 4]

[0098] In a further embodiment, the properties of the wet-laid hydroentangled PVOH web were as follows:

[0099] [Table 5]

[0100] Example 2 The tensile strength of the webs containing the polyvinyl alcohol / pulp blend was compared to that of commercially available flushable wipes.

[0101] 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% to 300% by weight.

[0102] 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%.

[0103] There was no significant difference in wet strength between 50:50 PVOH:Lyocell and 80:20 PVOH:Lyocell fabrics hydroentangled at high specific energy (p>0.05).

[0104] Example 3 The dispersibility of polyvinyl alcohol / pulp blends in wastewater was compared with that of commercially available flushable wipes.

[0105] Tests were conducted to determine sewer dispersibility. Commercial wipes exhibited poor dispersibility, with less than 60% passing through a 5.6 mm sieve.

[0106] PVOH wet-laid 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.

[0107] 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.

[0108] 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.

[0109] PVOH 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 of the hydroentangled, wet-laid fabrics. Commercially available flushable wipes passed the drainage test for dispersibility, with over 50% by weight passing a 12.5 mm sieve.

[0110] Wet-laid hydroentangled polyvinyl alcohol-containing webs showed excellent results, with over 80% by weight passing through a 12.5 mm sieve.

[0111] Example 4 A hydroentangled wet-laid nonwoven polyvinyl alcohol / pulp fabric was compared to commercially available flushable wipes.

[0112] 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.

[0113] Webs containing polyvinyl alcohol, pulp and viscose / lyocell showed better dispersibility performance compared to commercially available flushable wipes.

[0114] The use of PVOH 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.

[0115] Example 5 In a further embodiment, the following parameters were used:

[0116] [Table 6] JPEG2025526176000008.jpg53170

[0117] 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.

Claims

1. 1. A method for producing a nonwoven product comprising polyvinyl alcohol fibers, comprising: a homopolymer polyvinyl alcohol having a degree of hydrolysis of 88% to 98% or more and a molecular weight in the range of 22,000 to 38,000; 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; a 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; extruding the molten composition to form an extrudate; forming the extrudate into molten fibers; drawing the molten fibers to form individual molten fibers or bundles of molten fibers; solidifying the molten fibers to form solid fibers or bundles of solid fibers; A method comprising:

2. 10. The method of claim 1, including forming the fibers into a nonwoven web by a method selected from carding, air laying, and wet laying.

3. 3. The method of claim 2, wherein the fibers are dried and then carded.

4. 4. The method of claim 2 or 3, wherein the fibers in the nonwoven web are bonded by a method selected from hydroentanglement, needlepunching, chemical bonding, or thermal bonding.

5. The method of any one of claims 1 to 4, comprising mixing the polyvinyl alcohol fibers with sustainable fibers.

6. 6. The method of claim 5, wherein the sustainable fiber is selected from the group consisting of lyocell, polylactic acid, polyhydroxyalkanoate, cellulose pulp, and mixtures thereof.

7. 7. The method of claim 6, wherein the polyvinyl alcohol fibers and lyocell fibers are mixed in a ratio of polyvinyl alcohol:lyocell ranging from 70:30 to 90:10% by weight, preferably 80:20% by weight.

8. 8. The method of claim 7, wherein the polyvinyl alcohol fibers and polylactic acid fibers are mixed in a ratio of polyvinyl alcohol:polylactic acid ranging from 70:30 to 90:10 weight percent.

9. 9. The method of claim 8, wherein the ratio of polyvinyl alcohol to polylactic acid is in the range of 80:20% by weight.

10. The carded web has a thickness of 60 to 40 gm －２ The method of claim 3 , wherein the surface has an areal density of

11. The carded web is 50 gm －２ The method of claim 10, wherein the surface has an areal density of

12. A nonwoven fibrous product made according to the method of any one of claims 1 to 11.

13. 13. The nonwoven fibrous product of claim 12, wherein the product is a wipe.

14. A nonwoven fibrous product comprising fibers of a homopolymer polyvinyl alcohol having a degree of hydrolysis of 88% or greater.

15. 15. The nonwoven fibrous product of claim 14, further comprising sustainable cellulosic fibers.

16. 16. The nonwoven fibrous product of claim 15, wherein the sustainable fibers are selected from lyocell, polylactic acid, polyhydroxyalkanoates, and mixtures thereof.

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