TWI892204B - Extruded polyvinyl alcohol fibres and fibrous products - Google Patents

Abstract

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 molecular weight in the range from 22,000 to 38,000; 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 a 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 250°C; extruding the melted composition to form an extrudate; forming the extrudate into molten fibres; drawing the molten fibres to form individual molten fibres or bundles of molten fibres; and allowing the molten fibres to solidify to form solid fibres or bundles of solid fibres.

Description

Extruded polyvinyl alcohol fibers and fiber products

The present invention relates to polyvinyl alcohol fibers, methods for making polyvinyl alcohol fibers, and products made from polyvinyl alcohol fibers. The present invention particularly, but not exclusively, relates to products comprising extruded polyvinyl alcohol fibers, methods for making extruded polyvinyl alcohol fibers, and products incorporating such fibers.

Polyvinyl alcohol (PVA) offers numerous advantages over polymers traditionally used to make nonwoven fiber products. It is soluble in water, particularly when heated, making it easy to recycle, reuse, and degrade in the environment.

Polyvinyl alcohol (PVA) is produced by hydrolysis of homopolymers or copolymers of polyvinyl acetate. Polyvinyl alcohol produced by partial or complete hydrolysis of homopolymeric polyvinyl acetate is called homopolymeric polyvinyl alcohol. The degree of hydrolysis determines the properties of the resulting polymer. Copolymeric polyvinyl alcohol or homopolymeric polyvinyl alcohol with a low degree of hydrolysis (LD) is easy to process, but its mechanical and chemical properties are relatively poor. Homopolymeric polyvinyl alcohol with a high degree of hydrolysis (HD), such as 85% or higher, has excellent properties but is not processable on equipment used for polyolefin nonwoven fiber production without degradation.

Polyvinyl alcohol is soluble in water, and traditionally, low-degree (LD) hydrolyzed polyvinyl alcohol is used to make fibers via solution spinning.

To improve water resistance, thermal steps such as heat stretching and chemical steps such as acetylation are required.

WO2017/046361 discloses a method for producing processable polyvinyl alcohol with a degree of hydrolysis greater than or equal to 98%.

WO2022/008521 discloses a method for producing processable polyvinyl alcohol with a degree of hydrolysis of 93% to 98% or higher.

WO2022/008516 discloses a method for producing plasticized polyvinyl alcohol having a degree of hydrolysis of 93 wt% to 98 wt% or higher.

According to a first aspect of the present invention, a method for producing polyvinyl alcohol fiber comprises the following steps: providing a polyvinyl alcohol composition, wherein the polyvinyl alcohol composition comprises homopolymer polyvinyl alcohol having a hydrolysis degree of 88 wt% to 98 wt% or higher and a weight average molecular weight 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-propylene glycol, 1,4-butylene glycol, 2-hydroxy-1,3-propylene glycol, 3-methyl-1,3-butylene glycol, 3,3-dimethyl-1,2-butylene glycol, polyethylene glycol 300, polyethylene glycol 400, alkoxylated polyethylene glycol, caprolactam, tricyclic trihydroxymethylpropane formaldehyde 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 aforementioned composition at a temperature of 190°C to 250°C; extruding the aforementioned molten composition to form an extrudate; forming the aforementioned extrudate into molten fibers; stretching the aforementioned molten fibers to form individual molten fibers or molten fiber bundles; and solidifying the aforementioned molten fibers to form solid fibers or solid fiber bundles.

The aforementioned degree of hydrolysis may be 95wt% to 98wt%, for example, 93wt% to 95wt%.

In a specific embodiment, the molecular weight of the homopolymer polyvinyl alcohol can be 14,000 to 35,000.

The molecular weights in this specification are weight average molecular weights and are measured using conventional liquid chromatography techniques.

In a specific embodiment, the aforementioned composition can be melted at a temperature of 220°C to 240°C, for example, 220°C to 230°C.

The melt flow index (MFI) of the polyvinyl alcohol composition of the present invention may be 30 to 80 g/10 min, for example, 50 to 75 g/10 min, for example, 70 to 75 g/10 min. The melt flow index mentioned in this specification is measured by conventional techniques at 230°C using a 10 kg weight.

The polyvinyl alcohol composition of the present invention is stable at its melting and extrusion temperatures. Polyvinyl alcohol without the plasticizers and stabilizers disclosed in this specification, specifically homopolymers with a high degree of hydrolysis, may decompose at the temperatures required for melting and extrusion processing.

The advantageous polyvinyl alcohol fibers of the present invention can be processed on a commercial scale using conventional fiber processing equipment.

The polyvinyl alcohol according to the present invention can be processed into filaments or fibers. These filaments or fibers can be converted into staple fibers suitable for carding, wet-laid web formation, and air-laid web formation by crimping and cutting, thereby forming a range of nonwoven products.

The advantageous polyvinyl alcohol fibers of the present invention can be processed on a commercial scale, for example using equipment operating at 4,500 m/min.

The stable polyvinyl alcohol polymer used in the present invention can be produced according to WO2022/008516 and WO2022/008521; the disclosures of these international application publications are incorporated herein by reference for all purposes.

The polyvinyl alcohol composition can be produced by a method comprising the following steps: introducing a polyvinyl alcohol polymer having a degree of hydrolysis of 88 wt% to 98 wt% or more into a mixing reactor, wherein the polyvinyl alcohol polymer comprises homopolymer polyvinyl alcohol or a blend thereof; wherein the mixing reactor comprises a mixing chamber having a main inlet, a main outlet, and at least two mutually engaging components extending between the main inlet and the main outlet, wherein the components are arranged to apply shear forces to the polymer as it is transported from the inlet through a reaction zone to the outlet; one or more secondary inlets disposed downstream of the main inlet for introducing a reaction mixture comprising a processing aid, a plasticizer, and a reactive stabilizer into the mixing chamber; The invention further comprises introducing a reaction mixture into the chamber to form a reaction mixture; wherein the plasticizer is selected from the group disclosed above; wherein the reactive stabilizer is selected from the group consisting of sodium stearate, potassium oleate, sodium benzoate, calcium stearate, stearic acid, dimethylpropionic acid, and mixtures thereof; wherein the mixing chamber comprises a plurality of heating zones arranged to subject the mixture to a temperature profile such that the temperature increases from the inlet to the outlet; a secondary outlet located between the reaction zone and the primary outlet, the secondary outlet being arranged to allow removal of a processing agent from the chamber; reacting the processing agent, plasticizer, and polymer in the reaction zone to form a plasticized polymer; and passing the plasticized polymer through the primary outlet.

The reactive mixing apparatus of the present invention typically utilizes an extruder to allow a processing aid and a plasticizer to react with polyvinyl alcohol or a blend thereof without decomposing the polymer. All or most of the processing aid is then removed from a secondary outlet to obtain plasticized polyvinyl alcohol or a blend thereof.

The use of a reactive stabilizer can advantageously reduce the degree of degradation during melt processing. This allows homopolymer polyvinyl alcohol with a high degree of hydrolysis, such as 88 wt% or higher, to be processed into fibers or pellets, which can then be extruded into fibers.

The amount of the reactive stabilizer used may be from about 0.1 wt% to about 5 wt%, for example, from about 0.1 wt% to about 3 wt%, for example, from 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 stabilizer of the present invention can reduce the degree of degradation of the aforementioned polymers during processing. Homopolymer polyvinyl alcohol is difficult to process because it degrades at the required high temperatures. This tendency to degrade leads to the use of polyvinyl alcohol copolymers, with the attendant loss of engineering properties. This can be determined by UV spectroscopy analysis of the conjugated groups in the aforementioned polymers. Sodium benzoate has been found to be particularly effective.

The use of homopolymeric polyvinyl alcohol is particularly advantageous.

In a specific embodiment of the present invention, homopolymer polyvinyl alcohol is produced by hydrolysis of homopolymer polyvinyl acetate, with a degree of hydrolysis of 93 wt% or greater. 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.

The polyvinyl alcohol polymer of the present invention can have high tensile strength and flexibility.

Polyvinyl alcohol can be produced by hydrolysis of homopolymerized polyvinyl acetate, wherein the degree of hydrolysis is 88 wt% to 98 wt%, such as 93 wt% to less than 98 wt%, such as 93 wt% to 97 wt%, such as 93 wt% to 95 wt%.

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.

Blends of polyvinyl alcohols with the same molecular weight but different degrees of hydrolysis can be combined. Blending different grades of polyvinyl alcohol can improve the properties of the resulting polymer, such as melt strength.

For fiber production, two polyvinyl alcohol polymers with molecular weights of 22,000 to 38,000 can be blended, namely a first polymer with a low degree of hydrolysis and a second polymer with a high degree of hydrolysis, in a weight ratio of 40:60 to 60:40, for example, about 50:50.

The blend of polymers of varying molecular weights is selected based on the desired physical properties of the finished product. This may require the use of materials of varying molecular weights. The use of more than two polymers of varying molecular weights may be advantageous. The use of polymers of a single molecular weight is not excluded.

The use of blends allows for control of polymer viscosity. Selecting a stabilizer according to the present invention allows for the use of a blend with the desired viscosity without sacrificing other properties. Alternatively, the use of blends allows for the use of polyvinyl alcohol with one or more stabilizers while maintaining viscosity or other properties, enabling the production 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 compounds having a boiling point lower than the boiling point or melting point of the plasticizer. For cost and environmental reasons, water is preferably used.

Two or more plasticizers may be used.

When a mixture of plasticizers is used, a binary mixture is ideal.

In one embodiment, the plasticizer can 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 plasticizer in the formulation may be from about 15 wt % to about 30 wt %.

The polymer compositions and fibers of the present invention may not contain any or any substantial amount of water-soluble salts, oils, waxes, or ethylene homopolymers or copolymers.

The method of the present invention offers numerous advantages. It allows for the formation of heat-processable polyvinyl alcohol (PVA) while eliminating plastic pollution. Heat-processable PVA can be used to produce economical and highly functional fibers. PVA is water-soluble, environmentally non-toxic, and inherently biodegradable. Hydrophilic polymers such as PVA degrade more rapidly in the environment than hydrophobic polymers and do not exhibit bioaccumulation. Thermoplastic PVA can be mechanically recycled into pellets for reuse.

The fibers of the present invention can advantageously have a smaller diameter. Fibers with a smaller diameter have a larger surface area, which can be beneficial for air filtration, such as in a face mask. Finer fibers can also have a softer texture. Furthermore, finer fibers can also have an increased biodegradation rate after use.

According to a second aspect of the present invention, a nonwoven product is provided, comprising heat-processable homopolymer polyvinyl alcohol fiber produced according to the first aspect of the present invention, wherein the fiber has a degree of hydrolysis of 88 wt% or more.

According to a third aspect of the present invention, a nonwoven fiber product is provided, comprising homopolymer polyvinyl alcohol fiber having a degree of hydrolysis of 88 wt% or higher.

ISO 9092 defines nonwoven products as engineered fiber components that are primarily planar. The design standards specified are based on the overall structure of the engineered fiber component being achieved by physical and/or chemical means other than weaving, knitting, or papermaking.

The homopolymeric polyvinyl alcohol fibers of the present invention offer numerous 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. Homopolymeric polyvinyl alcohol fibers surprisingly exhibit all of these properties. In contrast, copolymers can only compromise and provide one or more of these properties at the expense of others. The fibers and products of the present invention possess a desirable monomaterial structure that does not suffer from these drawbacks.

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

The fibers of the present invention are produced by extruding filaments of molten polyvinyl alcohol polymer through a nozzle having small orifices, such as those with a diameter of 0.25 mm. These extruded filaments can be drawn using guide rolls rotating at different speeds to form a multifilament bundle. The multifilament bundle can be crimped by applying heat, then shaped using toothed or grooved rolls and cut using rotating blades to provide fibers of the desired length. Using a specific fiber length allows compatibility with various nonwoven fiber processing techniques.

The following extrusion and stretching conditions can be used.

The extrusion temperature used can be between 200°C and 250°C, ideally between 210°C and 247°C.

The number of filaments in a fiber can range from 24 to 72, depending on the equipment used. Using fibers containing 50 to 72 filaments can improve the cohesion of the filament bundles during drawing and enable higher draw ratios. A larger number of filaments allows the tensile force applied during drawing to be distributed among a larger number of filaments.

The rotational speed of the first guide roll can be between 200 and 310 m/min. Using a first guide roll speed higher than 300 m/min may increase the frequency of melt fracture. The optimal speed of the first guide roll can be approximately 295 m/min. The rotational speed of the fifth guide roll can be between 350 and 1665 m/min. The rotational speeds of the second through fourth guide rolls can be intermediate values. Using 72 filaments can achieve a higher draw ratio, resulting in finer fibers of 3 dtex or greater at a fifth guide roll speed of 500 rpm or higher.

Metering pump speed can be used. Using a metering pump can improve process stability. Shortening residence time can reduce the risk of thermal degradation of the polymer.

Spin finish can be applied to the filaments before the fibers pass through the guide rolls. Non-aqueous spin finishes such as Tallopol DT, Tallopon Biocone, or Vystat can be used. At a spin finish pump speed of 4 to 15 rpm, a spin finish content of 0.4 wt% to 4.7 wt% can be used.

A minimum of 0.4 wt% spinning finish may be used to provide sufficient cohesion between the filaments for drawing and winding.

The fibers according to the present invention may be laid down to form a nonwoven layer or web by various methods including carding, air-laying, or wet-laying. The fibers in the web may be bonded by a method selected from the group consisting of hydroentanglement, needle punching, chemical or adhesive bonding, and thermal bonding.

In the carding process, carding needles are used to separate and differentiate the fiber bundles to produce an oriented fiber network structure. Curled polyvinyl alcohol fibers can be used.

The relaxed 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 exemplary embodiments, drying is not required.

Use of the heat-processable fibers of the present invention allows for production on a commercial scale.

A blend of polyvinyl alcohol (PVOH) fiber and a sustainable fiber may be used, and the sustainable fiber may be selected, for example, from the group consisting of: Lyocell, polylactic acid (PLA), polyhydroxyalkanoate, and mixtures thereof.

A polyvinyl alcohol:lyocell blending ratio of 70wt%:30wt% to 90wt%:10wt%, ideally 80wt%:20wt%, or a polyvinyl alcohol:PLA ratio of 70wt%:30wt% to 90wt%:10wt%, ideally 80wt%:20wt%, can be used.

The carded web may have an area density of 60 to 40 g/m ² , for example about 50 g/m ² .

In one embodiment, 100% polyvinyl alcohol and 80 wt%:20 wt% polyvinyl alcohol:lyocell carded webs can be needle punched at a penetration depth of 9 mm, hydroentangled at 30 bar, or chemically bonded using an adhesive such as ethylene vinyl acetate (EVA).

Hot air bonding can be used to melt the adhesive to avoid excessive compression, where hot air is forced through the web, for example by convection.

Hot air bonding of 80wt%:20wt% PVA:PLA carded webs can be performed at 120°C for up to 2 minutes.

Air laying can be used, in which a turbulent air flow is used to produce an isotropic fiber network.

In one embodiment, the curly polyvinyl alcohol fibers can be cut into 5 mm lengths and blended with pulp fibers (approximately 2 mm) Georgia Pacific (GP) fibers.

The ratio of polyvinyl alcohol to cellulose used can be 80wt%:20wt% to 20wt%:80wt%, for example, about 50wt%:50wt%.

The areal density may be about 50 g/m ² , depending on the application, such as single or multiple use applications.

The polyvinyl alcohol fibers can be dried, for example, at 130°C for 10 minutes, to improve separation. In exemplary embodiments, drying is not required.

The airlaid web can be hydroentangled and then dried.

The fibers of the present invention have the advantage that webs containing polyvinyl alcohol fibers can be converted into high-strength hydroentangled air-laid nonwoven fabrics. It has been discovered that the fibers, particularly those containing warm-water-soluble polyvinyl alcohol, partially dissolve during the hydroentanglement process, thereby forming a strong but stiff fabric.

A wet-laid process can be used to form nonwovens containing hot water-soluble polyvinyl alcohol fibers. In this process, the polyvinyl alcohol fibers are dispersed in water and transferred to a foraminous conveyor belt, where the water is removed to deposit a fiber web.

In a specific embodiment, the fiber can be cut into a suitable length, such as 5 mm, and blended with pulp fiber, such as Södra Black, at a ratio of polyvinyl alcohol:pulp of 50 wt%:50 wt% to 20 wt%:80 wt%.

Lyocell fiber (1.4 dtex/5 mm) can be blended with polyvinyl alcohol (PVA) and paper pulp in a ratio of 50 wt%:50 wt% to 20 wt%:80 wt%.

The areal density may be about 60 g/m ² . This density may be used in the manufacture of flushable wipes.

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

The tensile strength is comparable to that of commercially available products. A blend with a ratio of 40 wt%: 40 wt%: 20 wt% of polyvinyl alcohol: pulp: lyocell exhibits a relatively high tensile strength of 11 to 13 N, typically around 12 N.

The present invention's pulp-entrained, hydroentangled wet-laid fabric exhibits relatively good tensile strength. Pulp fibers typically have a high ability to absorb liquid. After hydroentanglement, the wet-laid web remains saturated, causing the polyvinyl alcohol fibers to partially dissolve during the drying process. The polyvinyl alcohol fibers act as a binder, along with the hydrogen bonds formed between the pulp fibers.

The increase in specific energy during the hydroentanglement process can increase the dry tensile strength of fabrics incorporating Lyocell fibers.

Unless otherwise stated, percentages and other amounts mentioned in this specification are by weight and are selected from any of the listed ranges and total 100%.

1: Feed hopper

2: Extruder

3: Melt pump

4: Spinning components

5: Cold room

6: Spinning oil applicator

7: Roller

8: Guide Wire Roller

9: Winding Machine

10: Fiber

11: Fan

The present invention is further described by way of examples and with reference to the accompanying drawings, which are not intended to limit the present invention in any way. In the drawings: [Figure 1] is a schematic diagram of a fiber extrusion apparatus according to the present invention.

In a specific embodiment of the present invention, the following polyvinyl alcohol homopolymer composition can be used.

Polymer composition A

Polymer composition B

Polymer composition C

Polymer composition D

Polymer composition E

Polymer composition F

Polymer composition G

FIG1 shows an extrusion apparatus for polyvinyl alcohol fibers according to the present invention. A feed hopper (1) feeds pellets of a polyvinyl alcohol composition to an extruder (2). From the extruder, the molten polymer is conveyed to a melt pump (3), which meters the polymer to a spinning assembly (4). The spinning assembly (4) rotates the fiber (10) through a quenching chamber (5), which is supplied with cooling air by a fan (11). A spinning finish coater (6) applies a coating to the fiber (10). The fiber is then conveyed by a roller (7) to a series of guide rollers (8), which produce the stretched fiber. These fibers are then collected on a winder (9).

[Example]

Example 1

Multifilament polyvinyl alcohol fibers were extruded using the following parameters.

The fibers were crimped with the following operating parameters: IR heater temperature of 220°C, speed of 1.4 m/min, saw roll temperature of 100°C, and production rate of 17 g/h.

The following properties were observed using polyvinyl alcohol (PVOH) and polylactic acid (PLA).

The performance of air-laid hydroentangled PVOH webs is as follows.

The properties of wet-laid hydroentangled PVOH webs are as follows.

In other specific embodiments, the properties of the wet-laid hydroentangled PVOH web are as follows.

Example 2

The tensile strength of webs containing polyvinyl alcohol/paper pulp blends was compared to the tensile strength of commercially available flushable wipes.

The tensile strength was compared to that of detergent-saturated wipes. Commercial wipes were hand squeezed to remove excess detergent. The polyvinyl alcohol product of the present invention was saturated with excess detergent at an absorption level of 200 to 300 wt%.

Compared to a baseline flushable wipe and a wet-laid web hydroentangled at low specific energy (30 bar x 2 / 50 bar x 2), the wet-laid web hydroentangled at high specific energy (30 bar x 2 / 50 bar x 4) exhibited higher wet tensile strength. The increase in specific energy had a positive impact on the wet tensile strength of the hydroentangled wet-laid fabric, increasing it by approximately 100% to 170%.

There was no significant difference in wet strength between the 50:50 PVOH:Lysocell fabric and the 80:20 PVOH:Lysocell fabric hydroentangled at high specific energy (p>0.05).

Example 3

A polyvinyl alcohol/paper pulp blend was compared with a commercially available flushable wipe for dispersibility in drain lines.

Tests were conducted to determine dispersibility in sewer systems. Commercially available wipes showed low dispersibility, with less than 60% passing through a 5.6 mm screen.

Hydroentangled PVOH wet-laid fabrics at low specific energy (30 bar x 2/50 bar x 2) showed relatively good dispersion, with >70 wt% passing through a 5.6 mm screen. Shortening the lyocell fiber length from 5 mm to 3 mm had a positive effect on dispersion.

The dispersibility of wet-laid hydroentangled fabrics decreases with increasing specific energy (30 bar × 2 / 50 bar × 4). The fibers are more densely connected, promoting fiber rope formation.

After dispersibility testing, the hydroentangled wetlaid webs at high specific energy showed fragment sizes <4 cm, which is one of the alternative requirements to meet dispersibility targets in sewer systems.

PVOH fibers were successfully converted into wet-laid hydroentangled fabrics. Fabrics blended with pulp fibers exhibited good dry and wet tensile strength and dispersibility, while the incorporation of Lyocell fibers improved wet tensile strength but reduced the dispersibility of the hydroentangled wet-laid fabrics.

Commercially available flushable wipes passed the dispersibility test in drain lines, with over 50% by weight passing through a 12.5mm screen.

Wet-laid hydroentangled webs containing polyvinyl alcohol showed excellent results, with over 80 wt% passing through a 12.5 mm screen.

Example 4

Comparison of hydroentangled wet-laid polyvinyl alcohol/pulp nonwovens with commercially available flushable wipes.

Commercially available flushable wipes exhibited low dispersibility, with less than 60% passing through a 5.6mm screen. A hydroentangled wet-laid fabric incorporating 20% polyvinyl alcohol fibers and 80% pulp showed excellent results, with 90% passing through a 5.6mm screen.

Compared to commercially available flushable wipes, webs containing polyvinyl alcohol, paper pulp, and viscose/lyocell fibers exhibited better dispersion properties.

PVOH fibers are used in hydroentangled wet-laid fabrics blended with pulp fibers to improve dry tensile strength. The incorporation of viscose or lyocell fibers improves the fabric's wet strength. Using 40wt% polyvinyl alcohol, 40wt% pulp, and 20wt% viscose fiber achieves an excellent combination of wet strength and dispersion properties.

Example 5

In another specific embodiment, the following parameters are used.

The results show that the formula can be adjusted to a higher ratio to form finer fibers with a thickness of 2 dtex, thereby achieving higher melt strength.

Claims (15)

A method for producing a nonwoven product containing polyvinyl alcohol fibers comprises the following steps: Providing a polyvinyl alcohol composition comprising homopolymeric polyvinyl alcohol having a degree of hydrolysis of 88% to 98% or higher and a molecular weight 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-propylene glycol, 1,4-butylene glycol, 2-hydroxy-1,3-propylene glycol, 3-methyl-1,3-butylene glycol, 3,3-dimethyl-1,2-butylene glycol, polyethylene glycol 300, polyethylene glycol 400, alkoxylated polyethylene glycol, caprolactam, tricyclotrihydroxymethylpropane methylacetal, 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; The composition is melted at a temperature of 190°C to 250°C to form a molten composition; The molten composition is extruded to form an extrudate; The extrudate is formed into molten fibers; The molten fibers are stretched to form individual molten fibers or molten fiber bundles; and The molten fibers are solidified to form solid fibers or solid fiber bundles. The method of claim 1, comprising forming the fibers into a nonwoven web by a method selected from carding, air-laying and wet-laying. The method of claim 2, wherein the fiber is dried and then combed. The method of claim 2 or 3, wherein the fibers in the nonwoven web are bonded by a method selected from hydroentanglement, needle punching, chemical bonding, or thermal bonding. The method of any one of claims 1 to 3, comprising the step of blending the polyvinyl alcohol fiber with a sustainable fiber. The method of any one of claims 1 to 3, wherein the sustainable fiber is selected from the group consisting of lyocell, polylactic acid, polyhydroxyalkanoate, cellulose pulp, and mixtures thereof. The method of claim 6, wherein the polyvinyl alcohol fiber and the lyocell fiber are blended in a ratio of polyvinyl alcohol: lyocell of 70 wt%:30 wt% to 90 wt%:10 wt%. The method of claim 7, wherein the polyvinyl alcohol fiber and the polylactic acid fiber are blended in a ratio of polyvinyl alcohol:polylactic acid of 70 wt%:30 wt% to 90 wt%:10 wt%. The method of claim 8, wherein the ratio of polyvinyl alcohol to polylactic acid is 80 wt% to 20 wt%. The method of claim 3, wherein the carded web has an area density of 60 to 40 g/m ² . The method of claim 10, wherein the carded web has an area density of 50 g/m ² . A nonwoven fiber product manufactured according to the method of any one of claims 1 to 11. The nonwoven fiber product of claim 12, wherein the product is a wipe. The nonwoven fiber product as described in claim 12 or 13, further comprising sustainable cellulose fiber. The nonwoven fiber product of claim 14, wherein the sustainable fiber is selected from lyocell, polylactic acid, polyhydroxyalkanoate, and mixtures thereof.