TWI900195B - Nonwoven fabric for washable and manufacture method - Google Patents

Abstract

A nonwoven fabric for washable is provided in some embodiments of the present disclosure, including: a base layer and a water resistant anti-pilling layer. The base layer has a softness coefficient of from 40 to 140, in which the softness coefficient is tested according to method A in JIS L1096-2010 standard test. The water resistant anti-pilling layer is adhered to the base layer and includes a composition including polyurethane. A covalent bond exists between the base layer and the water resistant anti-pilling layer, and the covalent bond is an amide functional group bond, a urethane functional group bond, a urea functional group bond or a combination thereof. A weight percentage of isocyanate groups in the composition is not lower than 1.2%. A method of manufacturing a washable nonwoven fabric is also provided in some embodiments of the present disclosure.

Description

Washable nonwoven fabric and preparation method thereof

This disclosure relates to washable nonwoven fabrics and methods for preparing the same.

Nonwovens are widely used due to their environmental advantages of short production times and low carbon emissions. However, they are known to have issues such as lack of softness, poor pilling resistance, and inability to withstand repeated washing.

Chinese Patent Publication No. CN 105051279B discloses a method for improving the permeability and absorbency of nonwoven fabrics to highly viscous liquids and enhancing their softness by alternating non-thermally bonded and thermally bonded areas on the surface of the nonwoven fabric, replacing the conventional overall thermally bonded design. However, this prior application does not explore how to enhance anti-pilling properties or provide technical guidance for washability. Furthermore, the alternating non-thermally bonded and thermally bonded areas increases manufacturing complexity and prolongs production time.

US Patent Publication No. US20140315461A1 discloses the use of a hydrophobic agent to modify cellulose fibers to enhance their softness and water resistance. However, this prior application does not explore how to improve anti-pilling properties. Furthermore, the addition of a hydrophobic agent to modify the fibers complicates the manufacturing process and increases production time.

US Patent Publication No. 20040045144A1 discloses mechanical treatment of nonwoven fabrics (e.g., washing in a rope-like form) to enhance their softness. However, this prior application did not explore how to improve pilling resistance, and the resulting fabrics struggled to meet washability requirements.

US Patent Publication Nos. US20050022321A1 and US20030157854A1 disclose methods for improving the pilling resistance of nonwoven fabrics by applying an acrylic resin or hydrophilic silicone to the fabric. However, these prior patents do not explore methods for enhancing softness and washability.

US Patent Publication No. 20030221301A1 discloses physical treatment of nonwoven fabrics (e.g., using a sintering machine, hot water, or pressure) to reduce pilling. However, this prior application did not explore how to improve softness, and the resulting fabrics struggled to meet washability requirements.

Chinese Patent No. CN 217479700 U discloses methods for increasing surface pilling resistance by using an oil-based polyurethane adhesive to bond fibers together at their intersections to secure the ends, or by increasing the stitch density of the fiber web. However, both of these processes increase manufacturing complexity and production time. The adhesive also stiffens the resulting fabric, reducing its flexibility. Furthermore, the adhesive itself easily falls off the fiber layer after washing, making it difficult to meet washability requirements.

Therefore, the challenge is to provide washable nonwovens that simultaneously enhance softness, resist pilling, and pass washability testing standards, while also ensuring the environmental safety of the manufacturing process.

Some embodiments of the present disclosure provide a washable nonwoven fabric comprising a base layer and a washable anti-pilling layer. The base layer has a softness factor of 40 to 140, as measured according to Method A of JIS L1096-2010. The washable anti-pilling layer is disposed on the base layer and comprises a polyurethane composition. The washable anti-pilling layer is disposed on at least one surface layer or a backing layer of the base layer via a covalent bond with the base layer. The covalent bond is an amide functional group bond, a urethane functional group bond, a urea functional group bond, or a combination thereof. The base layer has a plurality of hydroxyl groups, a plurality of carboxyl groups, a plurality of amine groups, or a combination thereof, and the polyurethane has a plurality of isocyanate groups, wherein the weight percentage of the plurality of isocyanate groups in the composition is not less than 1.2%, based on 100% of the total weight of the composition. The amide functional group linkage is formed by the reaction of the plurality of isocyanate groups in the water-resistant anti-pilling layer with the plurality of hydroxyl groups in the base layer. The urethane functional group linkage is formed by the reaction of the plurality of isocyanate groups in the water-resistant anti-pilling layer with the plurality of carboxyl groups in the base layer. The urea functional group linkage is formed by the reaction of the plurality of isocyanate groups in the water-resistant anti-pilling layer with the plurality of amine groups in the base layer.

When describing "polyurethane" (PU), it refers to a type of polymer containing characteristic urethane units in the main chain. It can be called polyurethane or polyurethane.

In some embodiments, the base layer comprises polyester fibers, polyamide fibers, or a combination thereof.

In some embodiments, the fiber fineness in the base layer is 0.01 denier to 7 denier.

In some embodiments, the cross-sectional configuration of the fibers in the substrate layer is a hollow type, an island-in-the-sea type, a core-in-sheath type, a side-by-side type, or a segmented orange structure.

In some embodiments, the base layer has a bulk density of 0.2 g/cm3 to 0.5 g/cm3.

In some embodiments, the weight percentage of the washable anti-pilling layer is 1% to 10% based on the total weight of the washable nonwoven fabric being 100%.

In some embodiments, the polyurethane composition comprises polyester units, polyether units, or a combination thereof.

Some embodiments of the present disclosure provide a method for preparing a washable nonwoven fabric, comprising: providing a base layer; providing a polyol and a crosslinking agent; mixing the polyol and the crosslinking agent so that the hydroxyl group of the polyol and the isocyanate group of the crosslinking agent are bonded to form a prepolymer having a urethane unit; and attaching the prepolymer to the base layer to allow the prepolymer to undergo a crosslinking reaction with moisture (the prepolymer undergoes a crosslinking reaction between the molecules of the prepolymer after being induced by water molecules in the water vapor in the air). ) to form a composition comprising polyurethane, and simultaneously react with the functional groups of the base layer to form covalent bonds, thereby obtaining a water-resistant and anti-pilling layer attached to the base layer. The covalent bonds are amide functional groups, urethane functional groups, urea functional groups, or a combination thereof, and the prepolymer has a plurality of isocyanate groups, and when the total weight of the prepolymer is 100%, the weight percentage of the plurality of isocyanate groups in the prepolymer is not less than 1.2%.

In some embodiments, the humidity is water vapor in the air.

In some embodiments, the base layer is a nonwoven fabric prepared by a water rolling method or a needle rolling method.

In some embodiments, the polyol comprises polyester polyol, polyether polyol, trihydroxymethylpropane, trihydroxymethylethane, cyclohexanedimethanol, neopentyl glycol, trimethylpentanediol, pentaerythritol, or a combination thereof. These materials may be used individually or in combination.

In some embodiments, polyester polyols are obtained by condensation reaction of alcohols and carboxylic acids.

In some embodiments, the polyether polyol comprises polyethylene glycol, poly-1,3-propylene glycol, poly-1,2-propylene glycol, polytetramethylene ether glycol, poly-1,6-hexanediol, poly-2-methyl-1,3-propanediol, poly-2-ethyl-1,2-hydroxymethyl-1,3-propanediol, polyethylene glycol monomethyl ether, polyethylene glycol/polypropylene glycol copolymer, or a combination thereof.

In some embodiments, the polyol comprises a polyester polyol and a polyether polyol. Either one of the two can be used alone or in combination. The weight ratio of the polyester polyol to the polyether polyol is 0.5:1 to 10:1.

In some embodiments, the weight ratio of the polyol to the crosslinking agent is 2:1 to 9:1.

In some embodiments, the crosslinking agent comprises an isocyanate.

In some embodiments, amide-functional linkages are formed by reacting a plurality of isocyanate groups of the prepolymer with a plurality of hydroxyl groups of the substrate; urethane-functional linkages are formed by reacting a plurality of isocyanate groups of the prepolymer with a plurality of carboxyl groups of the substrate; and urea-functional linkages are formed by reacting a plurality of isocyanate groups of the prepolymer with a plurality of amine groups of the substrate.

In some embodiments, the base layer has a plurality of hydroxyl groups, a plurality of carboxyl groups, a plurality of amine groups, or a combination thereof.

100:Method

S110, S120, S130, S140: Steps

Various aspects of the present disclosure are best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that, in accordance with standard practice in the industry, the various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

Figure 1 shows a flow chart of a method for preparing washable nonwoven fabrics.

Figure 2 shows a comparison of the anti-pilling effects (expressed as pilling resistance) of Comparative Examples 5 to 11 (C5 to C11), Experimental Examples 11, and Experimental Examples 12 (E11 and E12) in Table 3.

The following disclosure provides numerous different embodiments for implementing various features of the subject matter. Specific examples of components, values, materials, configurations, and the like are described below to simplify the disclosure. These are, of course, merely examples and not limitations. For example, in the following description, forming a first feature on or above a second feature may include embodiments in which the first and second features are directly in contact, and may also include embodiments in which an additional feature is formed between the first and second features, such that the first and second features are not in direct contact. Furthermore, the disclosure may refer to repeated reference numbers and/or letters throughout the various examples. This repetition is for simplicity and clarity and does not in itself indicate a relationship between the various embodiments and/or configurations discussed.

The present disclosure provides a washable nonwoven fabric and a method for preparing the washable nonwoven fabric, comprising providing a base layer with softness (softness coefficient of 40 to 140) and good dimensional stability (5% modulus coefficient can be basically maintained above 3 Newtons) and coating a washable anti-pilling layer comprising a polyurethane composition on the base layer. Polyurethane compositions are environmentally friendly, requiring no chemical solvents during their synthesis. Furthermore, due to their inherent structural properties, they can undergo chain cross-linking reactions within their molecules, induced by moisture (water vapor in the air) or external moisture. This enhances the covalent bonding within these cross-links and simultaneously forms covalent bonds with the substrate. These multiple cross-linking reactions significantly enhance both pilling resistance and washability.

This disclosure discloses that the provision of a washable anti-pilling layer not only completely compensates for the reduced anti-pilling performance associated with increased softness, but also further enhances washability. This allows washable nonwovens to simultaneously enhance both softness and anti-pilling and washability, thereby expanding the application of nonwovens to various applications, such as durable apparel, medical protective clothing, industrial isolation clothing, home furnishings, furniture fabrics, toys, shoes and bags, and more.

Please refer to FIG. 1 , which shows a flow chart of a method 100 for preparing a washable nonwoven fabric, including steps S110 to S140 .

Step S110: Provide a base layer.

In some embodiments, the base layer comprises polyester fiber, polyamide fiber, or a combination thereof. In some embodiments, the base layer is a nonwoven fabric produced by a water-rolling or needle-rolling process. In some embodiments, after obtaining the nonwoven base fabric by water-rolling, the nonwoven base fabric may be further subjected to a refining process (e.g., a fiber opening process) to increase the fineness of the nonwoven base fabric, thereby obtaining a nonwoven fabric with enhanced softness for use as the base layer. However, since increased softness is achieved by increasing fiber fineness, this increased softness often results in a decrease in anti-pilling performance.

In some embodiments, the fiber cross-section of the base layer has a hollow, island-in-the-sea, core-in-sheath, side-by-side, or segmented structure.

In some embodiments, the fiber fineness (total denier) of the base layer is between 0.01 and 7 denier, such as 0.01, 0.1, 0.5, 1, 2, 3, 4, 5, 7, or values in between. Too low a fineness may result in insufficient anti-pilling properties, while too high a fineness may result in insufficient softness. In some embodiments, the base layer has a bulk density between 0.2 and 0.5 g/cm³, such as 0.2, 0.3, 0.4, 0.5 g/cm³, or values in between. Too low a bulk density may result in insufficient modulus and, consequently, insufficient dimensional stability. Too high a bulk density may result in insufficient breathability.

In some embodiments, the base layer has a softness modulus of 40 to 140 (e.g., 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or values in the aforementioned ranges), as measured according to Method A of JIS L1096-2010. A softness modulus that is too high will result in a reduced anti-pilling effect. A softness modulus that is too low will be difficult to apply in practice.

Step S120: Provide polyol and crosslinking agent.

In some embodiments, the polyol includes polyester polyol, polyether polyol, trihydroxymethylpropane, trihydroxymethylethane, cyclohexanedimethanol, neopentyl glycol, trimethylpentanediol, pentaerythritol, or a combination thereof. In other words, whether any of the aforementioned materials is used alone or in combination with two or more, the present disclosure encompasses these materials.

In some embodiments, polyester polyols are obtained by condensing alcohols and carboxylic acids. In some embodiments, polyester polyols are obtained by condensing polyols having 2 to 12 carbon atoms (preferably 2 to 6 carbon atoms) (alcohols as functional groups) with polycarboxylic acids having 2 to 12 carbon atoms (carboxylic acids as functional groups). Polycarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and isomeric naphthalene dicarboxylic acids. In some embodiments, when phthalic acid, isophthalic acid, terephthalic acid, or isomeric naphthalene dicarboxylic acids are selected as the polycarboxylic acid, the resulting polyester polyol exhibits better pilling resistance. In some embodiments, the polyether polyol comprises polyethylene glycol, poly-1,3-propylene glycol, poly-1,2-propylene glycol, polytetramethylene ether glycol, poly-1,6-hexanediol, poly-2-methyl-1,3-propanediol, poly-2-ethyl-1,2-hydroxymethyl-1,3-propanediol, polyethylene glycol monomethyl ether, polyethylene glycol/polypropylene glycol copolymer, or a combination thereof.

In some embodiments, the polyol comprises a polyester polyol and a polyether polyol, and the weight ratio of the polyester polyol to the polyether polyol is between 0.5:1 and 10:1, for example, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or values within these ranges. It is understood that, compared to a polyol alone, the combination of a polyether polyol and a polyester polyol can enhance the softness of the finished product (washable nonwoven fabric). Therefore, the lower the weight ratio, the higher the softness. By adjusting the weight ratio within this range, the softness of the washable nonwoven fabric can be controlled within the applicable range of the fabric.

In some embodiments, the crosslinking agent comprises an isocyanate, such as an ester having a cyanate group at one or both end groups.

In step S130, a polyol and a crosslinking agent are mixed so that the hydroxyl groups of the polyol and the isocyanate groups of the crosslinking agent are bonded to form a prepolymer having urethane units.

In some embodiments, the weight ratio of the polyol to the crosslinking agent is between 2:1 and 9:1, for example, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or values within the aforementioned ranges, to ensure sufficient reaction between the two and avoid excess raw materials. In some embodiments, step S130 is followed by a heating step (e.g., heating at 60°C to 95°C) to enhance the efficiency of prepolymer formation. In some embodiments, step S130 is performed until the weight percentage of isocyanate groups is less than 10% to ensure sufficient reaction.

In step S140, a prepolymer is attached to the base layer. The prepolymer undergoes a crosslinking reaction with moisture to form a composition comprising polyurethane. Simultaneously, the prepolymer reacts with functional groups of the base layer to form covalent bonds, thereby obtaining a washable and anti-pilling layer attached to the base layer. The covalent bonds are amide functional groups, urethane functional groups, urea functional groups, or a combination thereof.

In some embodiments, the prepolymer in step S140 has multiple isocyanate groups, and when the total weight of the prepolymer is taken as 100%, the weight percentage of the isocyanate groups in the prepolymer is not less than 1.2%. For example, it can be 1.2% to 10%, such as 1.2%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, or values within the foregoing ranges, or a range of values greater than 1.2%. If the weight percentage of the isocyanate groups is too low, the proportion of isocyanate groups that form covalent bonds with the functional groups of the base layer is insufficient, resulting in limited water resistance.

In some embodiments, the prepolymer undergoes chain crosslinking reactions with its internal molecular chains, induced by moisture in the air or applied moisture. This results in the washable, anti-pilling layer exhibiting multiple bonding types. For example, in addition to the prepolymer's original urethane units, the prepolymer also includes urea, allophanate, biuret, or combinations thereof. Therefore, compared to other polymer types, the use of polyurethane compositions as washable, anti-pilling layers offers advantages over other polymers, as the multiple crosslinking patterns protect the internal structure and enhance both anti-pilling and washability. In some embodiments, the polyurethane composition comprises polyester units, polyether units, or a combination thereof.

In some embodiments, after attaching the prepolymer to the base layer, the prepolymer or the polyurethane composition forms a covalent bond with the base layer (e.g., with the surface layer of the base layer or with the inner layer opposite the surface layer, where the inner layer refers to the portion not exposed to the outside). This creates a covalent bond between the base layer and the washable anti-pilling layer, enhancing the bonding strength between the two layers and further improving the anti-pilling properties and washability of the washable nonwoven fabric. In some embodiments, the covalent bond is an amide-functional bond (e.g., formed by the reaction of the isocyanate group of the water-resistant anti-pilling layer with the hydroxyl group of the base layer), a carbamate-functional bond (e.g., formed by the reaction of the isocyanate group of the water-resistant anti-pilling layer with the carboxyl group of the base layer), a urea-functional bond (e.g., formed by the reaction of the isocyanate group of the water-resistant anti-pilling layer with the amine group of the base layer), or a combination thereof.

In some embodiments, the weight percentage of the washable anti-pilling layer is 1% to 10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or values in the foregoing ranges, based on the total weight of the washable nonwoven fabric as 100%. A higher weight ratio may result in lower softness. A lower weight ratio may result in limited improvement in anti-pilling performance.

In some embodiments, the washable nonwoven fabric (a finished product formed by combining a base layer with a washable anti-pilling layer) has a pilling resistance rating greater than 3.5 (e.g., 3.5 or 4) for use as fabric. The pilling resistance rating is determined based on the pilling test using the Martindale Abrasion and Pilling Tester in accordance with ISO 12947-4:1998/Cor 1:2002.

In some embodiments, attaching the prepolymer to the base layer includes transferring the prepolymer resin onto the surface layer or into the inner structure of the base layer via gravure printing.

In the following description, multiple examples of this disclosure will be cited to conduct various analyses to verify the effectiveness of this disclosure.

Example 1, Preparation Method

1. Basal layer

Basal layers in Experimental Examples 1-4, 11-12 (E1 to E4, and E11 to E12) and Comparative Examples 7-8 (C7, C8)

Petal-shaped fibers with a fineness of approximately 1 to 10 denier (total denier) are hydro-rolled to form a nonwoven base fabric. "Petal-shaped fibers" herein refer to fibers spun using a mixed or composite spinning process and comprise two different components: 80% by weight polyethylene terephthalate (PET) and 20% by weight polyamide (PA). A cross-section of the fibers reveals an alternating arrangement of the two components. The nonwoven base fabric is then treated with hydraulic pressure/hot water flow to open the two fibers into ultrafine fibers with a fineness of less than 0.2 denier, thus forming the base layer.

Basal layer in Experimental Examples 5-10 (E5 to E10)

PET fibers with a fineness of approximately 1 to 3 denier (total denier) and a length of 45 mm to 65 mm are needle-rolled to obtain the base layer.

Comparative Examples 1-6, 9-11 (C1-C4, C5-C6, C9-C11) Base Layer (Unrefined)

Petal-shaped fibers with a fineness of approximately 1 to 10 denier (total denier) are hydrorolled to form a nonwoven base fabric (not subjected to a fiber opening process). "Petal-shaped fibers" herein refer to fibers spun using a mixed or composite spinning process and contain two different components: 80% by weight polyethylene terephthalate (PET) and 20% by weight polyamide (PA). A cross-section of the fiber reveals an alternating arrangement of the two components.

2. Preparation of washable anti-pilling layer materials

In a reaction vessel equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux cooler, 37.4 parts by weight of a polyester diol (polybutylene succinate, with an alcohol value of 37.4 mg/g of potassium hydroxide) and 49.1 parts by weight of a polyether diol (polyoxytrimethylene glycol, with an alcohol value of 56.1 mg/g of potassium hydroxide) were added. The mixture was then dehydrated under reduced pressure until the moisture content dropped to below 0.05% by weight. Next, 18.1 parts by weight of 4,4'-methylenediphenyl diisocyanate was added, and the temperature was raised to 90°C. The reaction was allowed to proceed for approximately 2 hours, until the weight percentage of isocyanate groups reached 2.8%. This yielded a prepolymer containing urethane units and terminal cyanate groups.

The following example describes the method for determining the isocyanate functional group (-NCO) content: Di-n-butylamine is dissolved in isopropyl alcohol and reacts with the isocyanate functional groups in the resin sample. The excess di-n-butylamine is then titrated with a standard hydrochloric acid solution to calculate the isocyanate functional group content in the resin sample.

The following illustrates the prepolymer formation reaction (Reaction Formula 1).

Theoretically, any polymer with specific end groups can be used in this reaction. Therefore, in Reaction 1, 4,4'-diphenylmethane diisocyanate is represented as OCN-R-NCO, and the polyester diol and polyether diol are represented as HO-R'-OH to more clearly illustrate the reaction process.

It should be emphasized that, in theory, the use of either polyester polyol or polyether diol in Reaction Equation 1 can facilitate the reaction. However, compared to simply adding polyester polyol, the addition of polyether diol can enhance the softness of the base layer.

3. Preparation of washable non-woven fabrics

The prepolymer containing urethane units obtained in step 2 was gravure-printed onto the base layer prepared in step 1 in a dot-like pattern, thereby forming a washable, anti-pilling layer on the surface or inner layer of the base layer. The washable, anti-pilling layer and the base layer together formed a washable nonwoven fabric (samples of Experimental Examples 1 to 12, Comparative Examples 1 to 4, and Comparative Examples 9 to 10).

It is important to emphasize that during the prepolymer preparation process, existing terminal cyanate groups, or terminal amine groups formed through further intramolecular cross-linking reactions induced by moisture in the air, can undergo further chain cross-linking reactions with internal molecular chains. This allows the washable, anti-pilling layer to contain, in addition to urethane units, urea-functional linkages, allophanate-functional linkages, biuret-functional linkages, or combinations thereof. For details, see Equations 2-1 through 2-4 below.

It's important to emphasize that the washable, anti-pilling layer must undergo a chemical reaction to form a covalent bond to the surface or inner layer of the base layer in order to enhance its washable, anti-pilling properties. For example, the sample in Comparative Example 11 demonstrates this. The surface layer in Example 11 is coated with a water-based PU, which only generates Van der Waals forces on the fiber surface. After a few washes, the anti-pilling effect is significantly reduced.

First, the prepolymer undergoes a moisture-induced reaction, with the two terminal groups reacting to form amino groups (Reaction Equation 2-1). The amino group-containing product then reacts with the prepolymer to form a product with a urea functional group bond (Reaction Equation 2-2).

At the same time, the prepolymer itself will react with the urethane units on the molecular chain through the end groups to produce a product with allophanate functional groups (Reaction Equation 2-3).

Reaction 2-3

Similarly, the prepolymer itself can react with the urea functional units on the molecular chain through the end groups to generate products with diurea functional groups (Reaction Formula 2-4).

It's also worth noting that when the prepolymer is transferred to the substrate by coating or embossing, it can crosslink with the substrate material (such as an alcohol or carboxylic acid), creating a covalent bond between the washable anti-pilling layer and the substrate, thereby enhancing the subsequent anti-pilling effect (pill resistance level). For details, please refer to the following Reaction Equation 3-1 (reaction of the prepolymer with an alcohol, exemplified here by the structure of a polyol) and Reaction Equation 3-2 (reaction of the prepolymer with a carboxylic acid, although the carboxylic acid structure here is presented with a carboxyl group as the terminal group. In theory, any carboxylic acid with a carboxyl terminal group can undergo the following reaction).

Example 2: Performance Testing

The samples prepared according to Example 1 (C1 to C10, and E1 to E12) were subjected to various standardized tests to obtain the values of various physical properties. The fabric performance of each sample prepared under different preparation conditions was compared (Tables 1 to 3). The following describes the methods for measuring the values of various physical properties.

Stiffness: Prepare a sample measuring 20 mm x 150 mm according to JIS L1096-2010 A (45-degree cantilever method). Place the short side of the sample on a smooth, horizontal platform with a scale line. Slide the sample along the slope. When one end of the sample contacts the slope, the position of the other end is measured using the scale.

Flexibility coefficient: This is performed according to JIS L1096A-2010 A (45-degree cantilever method). The sample's stiffness and thickness are measured. The stiffness is divided by the thickness to obtain the flexibility coefficient. The flexibility coefficient indicates the material's flexibility when subjected to gravity. A smaller coefficient indicates a more flexible material.

5% elongation modulus: The test is conducted in accordance with ISO 527, Plastics Tensile Test. The sample is cut into 30 mm x 150 mm specimens and subjected to a tensile test at a speed of 200 mm/min (with a clamp spacing of 100 mm). After the test is completed, the tensile strength value of the sample at 5% elongation is read.

Modulus coefficient: Divide the 5% elongation modulus of a nonwoven fabric by the sample thickness to obtain the modulus coefficient of the nonwoven fabric. The modulus coefficient indicates the dimensional stability of the material when subjected to tension. A smaller coefficient indicates that the material's structure is more likely to loosen when washed.

Pilling resistance: Pilling resistance is measured using the Martindale Abrasion and Pilling Tester (Pilling Grade) according to ISO 12947-4:1998/Cor 1:2002.

The comparative results of the fabric performance of each group of samples are shown in Tables 1 to 3. For easier comparison, the pilling resistance (corresponding to the anti-pilling effect) results of each group in Table 3 are summarized in Figure 2.

The results in Tables 1 and 2 show that samples C1 to C4, which have a nonwoven base layer with a fiber fineness greater than 8 denier (excluding 8 denier) and are directly applied with a washable anti-pilling layer, have a flexibility coefficient greater than 140, indicating that the fabric is too stiff. In contrast, samples E1 to E4, which have a fiber fineness less than 0.2 denier (excluding 0.2 denier), and samples E5 to E10, which have a fiber fineness of 4 denier, have a flexibility coefficient less than 140 and a modulus greater than 3 Newtons/mm, indicating greater flexibility and dimensional stability.

Furthermore, according to E9 and E10, it can be found that when the bulk density is lower (0.12 g/cm³ and 0.13 g/cm³), the modulus coefficient also decreases, resulting in a decrease in dimensional stability.

Note: "0 washes" indicates the sample has not been washed; "20 washes" indicates the sample has been washed 20 times before testing. Repeated wash/drying testing is performed using a washing machine that complies with AATCC-LP1 specifications and follows the AATCC-135 method developed by the American Textile Chemists Association.

For clarity, the following section analyzes the test results in Table 3 and Figure 2.

According to C5 and C6, the pilling resistance of nonwoven fabric samples obtained by the water-rolling method, when not scouring and not equipped with a washable anti-pilling layer, will decrease by 0.5 levels after washing.

Compared to C5 and C6 (no scouring, no washable anti-pilling layer), C7 and C8 (scouring, no washable anti-pilling layer) show that nonwoven fabric samples obtained by water rolling and then subjected to scouring to enhance softness show decreased pilling resistance. This indicates that while scouring can enhance softness, it also reduces the anti-pilling effect.

Compared to C5 and C6 (no scouring, no washable anti-pilling layer), C9 and C10 (no scouring, washable anti-pilling layer) show that nonwoven samples obtained by water rolling, if directly applied with a washable anti-pilling layer without scouring, show improved pilling resistance regardless of washing. This indicates that the washable anti-pilling layer can improve pilling resistance (enhancing the anti-pilling effect). Furthermore, after 20 washes, pilling resistance did not decrease and remained the same as before washing, indicating improved water resistance.

The aforementioned comparison between C5/C6 and C7/C8 shows that the softness of nonwoven samples obtained by the water-rolling process increases after scouring, but pilling resistance decreases (anti-pilling effectiveness decreases). Furthermore, compared to C9 and C10 (no scouring, with a washable anti-pilling layer), E11 and E12 (with scouring and a washable anti-pilling layer) show that the softness and anti-pilling effectiveness of samples (E11 and E12) are improved after scouring and then adding a washable anti-pilling layer. In other words, although the anti-pilling effect decreases after scouring, if a washable anti-pilling layer is applied, the pilling resistance can be restored to the same level as the untreated sample, regardless of whether it is washed or not, completely compensating for the loss of anti-pilling effect caused by scouring.

While scouring improves softness, it also reduces anti-pilling effectiveness. However, when combined with a washable anti-pilling layer, the anti-pilling effect is significantly enhanced, returning it to the same level as a sample with the washable anti-pilling layer applied directly without scouring. In other words, the washable anti-pilling layer compensates for the loss of anti-pilling effectiveness caused by the reduction in fiber fineness during scouring.

Compared to conventional nonwovens, the washable nonwovens provided in the experimental examples of this disclosure have achieved higher standards of softness and pilling resistance, making them suitable for a wider range of textile applications.

The foregoing outlines the features of some embodiments so that those skilled in the art may better understand the perspective of the present disclosure. Those skilled in the art should appreciate that they can readily use this disclosure as a basis for designing or modifying other processes and structures to achieve the same purposes and/or achieve the same advantages as the embodiments described herein. Those skilled in the art should also appreciate that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations are possible without departing from the spirit and scope of the present disclosure.

100:Method

S110, S120, S130, S140: Steps

Claims (18)

A washable nonwoven fabric comprises: A base layer having a softness factor of 40 to 140, wherein the softness factor is measured according to Method A of the JIS L1096-2010 standard; and A washable anti-pilling layer disposed on the base layer and comprising a polyurethane composition; The washable anti-pilling layer is disposed on at least one surface layer or a backing layer of the base layer via a covalent bond with the base layer; The covalent bond is an amide functional group bond, a urethane functional group bond, a urea functional group bond, or a combination thereof; The base layer has a plurality of hydroxyl groups, a plurality of carboxyl groups, a plurality of amine groups, or a combination thereof, and the polyurethane has a plurality of isocyanate groups, wherein the weight percentage of the plurality of isocyanate groups in the composition is not less than 1.2% when the total weight of the composition is taken as 100%; The amide functional group bond is formed by the reaction of the plurality of isocyanate groups of the water-resistant anti-pilling layer with the plurality of hydroxyl groups of the base layer; The urethane functional group bond is formed by the reaction of the plurality of isocyanate groups of the water-resistant anti-pilling layer with the plurality of carboxyl groups of the base layer; The urea functional group bond is formed by the reaction between the multiple isocyanate groups of the water-resistant anti-pilling layer and the multiple amine groups of the base layer. The washable nonwoven fabric according to claim 1, wherein the base layer comprises polyester fiber, polyamide fiber, or a combination thereof. The washable nonwoven fabric as claimed in claim 1, wherein the fiber cross-section of the base layer has a hollow type, an island-in-the-sea type, a core-sheath type, a side-by-side type, or a segmented orange structure. The washable nonwoven fabric as claimed in claim 1, wherein the fineness of the fibers in the base layer is 0.01 denier to 7 denier. The washable nonwoven fabric according to claim 1, wherein the base layer has a bulk density of 0.2 g/cm3 to 0.5 g/cm3. The washable non-woven fabric as claimed in claim 1, wherein the weight percentage of the washable anti-pilling layer is 1% to 10% based on the total weight of the washable non-woven fabric as 100%. The washable nonwoven fabric as claimed in claim 1, wherein the composition comprises polyester units, polyether units or a combination thereof. A method for preparing a washable nonwoven fabric comprises: Providing a base layer, wherein the base layer has a softness index of 40 to 140, as measured according to Method A of JIS L1096-2010; Providing a polyol and a crosslinking agent; Mixing the polyol and the crosslinking agent so that the hydroxyl groups of the polyol and the isocyanate groups of the crosslinking agent are bonded to form a prepolymer having urethane units; and The prepolymer is attached to the base layer and allowed to crosslink with moisture to form a composition comprising polyurethane. The prepolymer also reacts with functional groups of the base layer to form covalent bonds, thereby obtaining a water-resistant and anti-pilling layer attached to the base layer. The covalent bonds are amide functional groups, urethane functional groups, urea functional groups, or a combination thereof. The prepolymer has a plurality of isocyanate groups, and when the total weight of the prepolymer is 100%, the weight percentage of the plurality of isocyanate groups in the prepolymer is not less than 1.2%. The method of claim 8, wherein the humidity is water vapor in the air. The method of claim 8, wherein the base layer is a nonwoven fabric prepared by a water rolling method or a needle rolling method. The method of claim 8, wherein the polyol comprises polyester polyol, polyether polyol, trihydroxymethylpropane, trihydroxymethylethane, cyclohexanedimethanol, neopentyl glycol, trimethylpentanediol, pentaerythritol, or a combination thereof. The method of claim 11, wherein the polyester polyol is obtained by a condensation reaction between an alcohol and a carboxylic acid. The method of claim 11, wherein the polyether polyol comprises polyethylene glycol, poly-1,3-propylene glycol, poly-1,2-propylene glycol, polytetramethylene ether glycol, poly-1,6-hexanediol, poly-2-methyl-1,3-propanediol, poly-2-ethyl-1,2-hydroxymethyl-1,3-propanediol, polyethylene glycol monomethyl ether, polyethylene glycol/polypropylene glycol copolymer, or a combination thereof. The method as described in claim 11, wherein the polyol comprises the polyester polyol and the polyether polyol, and the mixing weight ratio of the polyester polyol to the polyether polyol is 0.5:1 to 10:1. The method of claim 8, wherein the weight ratio of the polyol to the crosslinking agent is 2:1 to 9:1. The method of claim 8, wherein the crosslinking agent comprises isocyanate. The method of claim 8, wherein the amide functional group bonding is formed by the reaction of the plurality of isocyanate groups of the prepolymer and the plurality of hydroxyl groups of the base layer; the urethane functional group bonding is formed by the reaction of the plurality of isocyanate groups of the prepolymer and the plurality of carboxyl groups of the base layer; and the urea functional group bonding is formed by the reaction of the plurality of isocyanate groups of the prepolymer and the plurality of amine groups of the base layer. The method of claim 8, wherein the base layer has a plurality of hydroxyl groups, a plurality of carboxyl groups, a plurality of amino groups, or a combination thereof.