High-dryness nonwoven fabric, method for producing the same, and absorbent article

Abstract

This application relates to the field of nonwoven fabrics, specifically a high-dryness nonwoven fabric, its preparation method, and absorbent articles. The fiber material constituting the nonwoven fabric is a core-sheath composite fiber, comprising a sheath and a core. At least a portion of the sheath melts, causing the composite fiber sheaths to thermally bond together to form adhesive points. The core material accounts for 20-80% of the total mass of the core-sheath composite fiber. The substrate of the sheath includes polyethylene resin, and the substrate of the core includes polyester resin, and at least one of polybutylene terephthalate resin or polypropylene terephthalate resin. The bulk density (0.2 kPa) of the nonwoven fabric is ≤3.9%, and the bulk density (0.2 kPa) of the woven fabric is ≤3.5%. This nonwoven fabric has a superior fiber structure, resulting in faster absorption and reduced reabsorption compared to nonwoven fabrics of the same basis weight.

Description

[0001] This application claims priority to patent application number 2025110204215 (the earlier application was filed on July 23, 2025, and the invention is entitled "High Dryness Nonwoven Fabric and Preparation Method Thereof, Core-Sheet Composite Fiber and Preparation Method Thereof, Absorbent Article"). Technical Field

[0002] This application relates to the field of nonwoven fabrics, and more specifically, to a high-dryness nonwoven fabric, its preparation method, and absorbent articles. Background Technology

[0003] Nonwoven fabric is generally referred to as nonwoven cloth. There are many types of nonwoven fabrics, with a very wide range of applications, including clothing, household goods, medical supplies, civil engineering, industry, agriculture and horticulture, and military defense. Furthermore, due to the diverse processing methods used, there are also various ways to classify nonwoven fabrics.

[0004] Hot-air nonwoven fabric, a bicomponent composite short fiber with a core and sheath, is a relatively new type of nonwoven material. Due to its unique feel, breathability, and filtration performance, it has played an irreplaceable role in the hygiene industry since its development. In recent years, with the improvement of people's living standards and the continuous pursuit of quality of life, hot-air nonwoven fabric has been increasingly widely used in absorbent products such as feminine hygiene products, baby diapers, and adult diapers.

[0005] PE / PET core-sheath composite fiber is a composite fiber produced by combining two polymers, PE and PET. Nonwoven fabrics made from this fiber are widely used in the sanitary materials industry. It possesses advantages such as a low melting point of the outer layer, a high melting point of the inner layer, and high fiber strength. After further processing and heat treatment, some of the sheath layer melts and bonds, while the remaining fibers retain their fibrous state, forming a network structure. This gives the hot-air nonwoven fabric a certain degree of structural stability and bulkiness.

[0006] However, for absorbent products, lightweight is becoming an increasingly important requirement, so hot-air nonwoven fabrics are also striving for greater lightness. To achieve this, lower basis weights are used. However, lower basis weights result in a smaller average thickness of the nonwoven fabric, making it more prone to rewetting. Conversely, increasing the basis weight slows down the absorption rate of the nonwoven fabric. This affects the liquid permeability of the absorbent product, leading to increased rewetting and resulting in a damp environment on the consumer's skin during use, negatively impacting the user experience.

[0007] As people's demands for quality of life continue to rise, ordinary PE / PET hot-air nonwoven fabrics can no longer meet the high-quality requirements for hygiene materials in order to pursue higher dryness during use. Based on this, those skilled in the art need to develop a nonwoven fabric with high dryness. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a high-dryness nonwoven fabric, its preparation method, and absorbent products.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, this application provides a nonwoven fabric in which the fiber material constituting the nonwoven fabric is a core-sheath composite fiber, the core-sheath composite fiber including a sheath and a core; at least a portion of the sheath melts, causing the composite fiber sheath to be thermally bonded to each other to form bonding points; the core material of the core-sheath composite fiber accounts for 20%-80% by mass, the substrate of the sheath includes polyethylene resin, the substrate of the core material includes polyester resin, and includes at least one of polybutylene terephthalate resin or polypropylene terephthalate resin;

[0011] The bulk density (0.2 kPa) of nonwoven fabric is ≤3.9%.

[0012] In some alternative implementations,

[0013] The bulk density (0.2 kPa) of the spun fabric is ≤3.5%; and / or

[0014] The bulk density (1.4 kPa) of the nonwoven fabric is ≤7.3%;

[0015] Preferably, the bulk density (1.4 kPa) of the nonwoven fabric is ≤6.9%.

[0016] In some alternative implementations, the crimp angle of the core-sheath composite fibers is 65°-130°;

[0017] Preferably, the crimp angle of the core-sheath composite fiber is 90°-120°.

[0018] In some alternative implementations, the core-sheath composite fiber has a crimp count of 10 to 25 mm.

[0019] Preferably, the number of crimps in the core-sheath composite fiber is 12-24 / 25mm.

[0020] In some alternative implementations, the average thickness of the nonwoven fabric is >0.40 mm;

[0021] Preferably, the average thickness of the nonwoven fabric is ≥0.45mm, more preferably ≥0.50mm;

[0022] The weight of nonwoven fabric is 16 g / m² to 30 g / m².

[0023] In some alternative implementations, the dry heat shrinkage rate of the core-sheath composite fiber is 0.3%-7%;

[0024] Preferably, the dry heat shrinkage rate of the core-sheath composite fiber is 0.5-5%; more preferably, the dry heat shrinkage rate of the core-sheath composite fiber is 0.5-2.2%.

[0025] In some alternative embodiments, the viscosity of the polyester resin is controlled between 0.8 dL / g and 1.3 dL / g.

[0026] In some alternative embodiments, the core material of the sheath-core composite fiber comprises a low-viscosity polyester resin, wherein the low-viscosity polyester resin is a similar polyester resin and the viscosity of the polyester resin is 0.5 dL / g-0.7 dL / g.

[0027] The amount of low-viscosity polyester resin in the total polyester resin should be controlled between 2wt% and 5wt%.

[0028] In some alternative implementations, the specific surface area of ​​the nonwoven fabric is ≥0.04m². 2 / g;

[0029] Preferably, the specific surface area of ​​the nonwoven fabric is ≥0.05m². 2 / g; further preferred specific surface area ≥0.07m² 2 / g, more preferably a specific surface area ≥0.08m² 2 / g, with an optimal specific surface area ≥0.11m² 2 / g.

[0030] In some alternative embodiments, the core-sheath composite fiber has a restricted eccentric structure, specifically d / R ≤ 33%; preferably d / R ≤ 15%; more preferably d / R ≤ 10%; and most preferably d / R ≤ 1%.

[0031] In some alternative embodiments, the fineness of the core-sheath composite fiber is 0.8 dtex-11 dtex; preferably 1 dtex-10 dtex.

[0032] In some alternative embodiments, the melt index (170°C·2.16Kg) of the polyethylene resin is 7.8-18g / 10min.

[0033] In some alternative implementations, nonwoven fabric is applied to the absorbent article, with the nonwoven fabric disposed on the absorbent core and on the side facing the human skin.

[0034] The nonwoven fabric of the first aspect of this application can be prepared using the nonwoven fabric preparation method provided in the second aspect.

[0035] Secondly, this application provides a method for preparing nonwoven fabric, including a fiber spinning process and a hot air process:

[0036] The fiber spinning process includes: using a polyester resin containing at least one or two of polybutylene terephthalate resin or polypropylene terephthalate resin as the core material; using a substrate containing polyethylene resin as the sheath material; spinning the core material and the sheath material to obtain core-sheath composite fiber filaments; and performing post-stretching, crimping, and heat setting on the core-sheath composite fiber filaments.

[0037] The hot air process includes: chopped fibers of the core-sheath composite fiber are combed and bonded with hot air to obtain nonwoven fabric.

[0038] In some alternative embodiments, the core material and the sheath material are spun to obtain core-sheath composite fiber nascent filaments, including:

[0039] Select a spinneret with a concentric or eccentric structure for spinning targets, and control the spinning temperature at 250℃-275℃ and the spinning speed at 1000m / min-1500m / min.

[0040] In some alternative embodiments, the core-sheath composite nascent fiber is post-stretched, including:

[0041] When post-stretching the nascent filaments of the core-sheath composite fiber, the stretching ratio should be controlled at 2-4 times; preferably 2.5-3.5 times.

[0042] In some optional embodiments, the core-sheath composite fiber nascent filament is crimped, including: when crimping the core-sheath composite fiber nascent filament, the crimping temperature is controlled at 58℃-90℃ and the crimping pressure is 0.07-0.44MPa.

[0043] In some optional embodiments, heat setting of the core-sheath composite fiber nascent filaments includes controlling the heat setting temperature at 110℃-125℃ and the drying time at 5min-15min.

[0044] In some alternative implementations, core-sheath composite fibers are selected as the fiber raw material for the nonwoven fabric, and the initial processing state of the fibers is short fibers, including:

[0045] The selected short fiber length is 38mm-51mm.

[0046] In some alternative embodiments, the resulting core-sheath composite fibers are combed, including:

[0047] The cut short fibers are placed on a carding machine for carding and laid into a web. The carding machine cylinder speed is 50-65 Hz, the doffer speed is 30-47 Hz, and the target basis weight of the fiber web is controlled to be 11-21 g / m².

[0048] In some alternative embodiments, the resulting core-sheath composite fibers are hot-air bonded, including:

[0049] The combed short fibers are processed at a temperature of 130-150℃ and a blower frequency of 35-55HZ for 3-20 seconds to bond them into a nonwoven fabric.

[0050] Preferably, the processing temperature is 130-145℃;

[0051] Preferably, the blower frequency is 35-45 Hz;

[0052] Preferably, the processing time is 3-10 seconds.

[0053] The core-sheath composite fiber used in the preparation method of the nonwoven fabric in the first aspect or the nonwoven fabric provided in the second aspect of this application can be the core-sheath composite fiber provided in the third aspect or the core-sheath composite fiber provided in the fourth aspect.

[0054] Thirdly, this application provides a core-sheath composite fiber, which includes a sheath and a core. The core material accounts for 20%-80% of the total mass of the core material. The substrate of the sheath includes polyethylene resin, and the substrate of the core material includes polyester resin, and includes at least one of polybutylene terephthalate resin or polypropylene terephthalate resin.

[0055] In some alternative embodiments, the crimp angle of the core-sheath composite fiber is 65°-130°; preferably 90°-120°.

[0056] In some alternative embodiments, the number of crimps of the core-sheath composite fiber is 10 to 25 mm, preferably 12 to 24.

[0057] In some alternative embodiments, the dry heat shrinkage rate of the core-sheath composite fiber is 0.3%-7%; preferably 0.5%-5%; more preferably 0.5%-2.2%.

[0058] In some alternative implementations, the viscosity of the core material substrate is controlled between 0.8 dL / g and 1.3 dL / g.

[0059] In some alternative embodiments, the core material of the sheath-core composite fiber also includes a low-viscosity polyester resin, wherein the low-viscosity polyester resin is of the same type and the viscosity of the low-viscosity polyester resin is 0.5 dL / g-0.7 dL / g;

[0060] The amount of low-viscosity polyester resin in the total polyester resin should be controlled between 2wt% and 5wt%.

[0061] In some alternative embodiments, the fineness of the core-sheath composite fiber is 0.8 dtex-11 dtex; preferably 1-10 dtex.

[0062] In some alternative embodiments, the core-sheath composite fiber has a restricted eccentric structure, specifically d / R ≤ 33%; preferably d / R ≤ 15%; more preferably d / R ≤ 10%; and most preferably d / R ≤ 1%.

[0063] The core-sheath composite fiber provided in the third aspect of this application can be prepared using the core-sheath composite fiber preparation method provided in the fourth aspect.

[0064] Fourthly, this application provides a method for preparing core-sheath composite fibers, comprising:

[0065] The core material is made of a polyester resin containing at least one or two of polybutylene terephthalate resin or polypropylene terephthalate resin, and the outer material is made of a polyethylene resin.

[0066] Core material and sheath material are spun to obtain core-sheath composite fiber nascent filaments; the core-sheath composite fiber nascent filaments are then subjected to post-stretching, crimping, and heat setting.

[0067] In some alternative embodiments, the core material and the sheath material are spun to obtain core-sheath composite fiber nascent filaments, including:

[0068] Select a spinneret with a concentric or eccentric structure for spinning targets, and control the spinning temperature at 250℃-275℃ and the spinning speed at 1000m / min-1500m / min.

[0069] In some alternative embodiments, the core-sheath composite nascent fiber is post-stretched, including:

[0070] When post-stretching the nascent filaments of the core-sheath composite fiber, the stretching ratio should be controlled to be 2-4 times, preferably 2.5-3.5 times.

[0071] In some alternative embodiments, the core-sheath composite fiber nascent filament is crimped, including:

[0072] When crimping the nascent filaments of the core-sheath composite fiber, the crimping temperature should be controlled at 58℃-90℃ and the crimping pressure at 0.07-0.44MPa.

[0073] In some alternative embodiments, the core-sheath composite nascent fiber is heat-set, including:

[0074] When heat-setting the nascent filaments of the core-sheath composite fiber, the heat-setting temperature should be controlled at 110℃-125℃ and the drying time should be 5min-15min.

[0075] Fifthly, this application provides an absorbent article in which the nonwoven fabric layer on the side facing the human skin relative to the absorbent core is the nonwoven fabric in any of the embodiments of the first aspect; or, the nonwoven fabric layer on the side facing the human skin relative to the absorbent core is a nonwoven fabric prepared by the method of preparing the nonwoven fabric in any of the embodiments of the second aspect.

[0076] Optionally, the surface nonwoven fabric in the absorbent article is the nonwoven fabric in any of the embodiments of the first aspect described above;

[0077] Optionally, the surface nonwoven fabric in the absorbent article is a nonwoven fabric prepared by the method for preparing nonwoven fabric in any of the embodiments of the second aspect described above.

[0078] In some alternative implementations, the absorbent product includes any one of the following: feminine hygiene pads, panty liners, diapers, pull-up diapers, nursing pads, or waterproof pads.

[0079] Compared with the prior art, the present invention has at least the following beneficial effects:

[0080] At the same basis weight, when the fiber structure is different, especially when the bulk density of the nonwoven fabric (0.2 kPa) is ≤3.9%, the nonwoven fabric has better permeability and faster permeation speed. When the fiber structure is different, especially when the bulk density of the nonwoven fabric (1.4 kPa) is ≤7.3%, the nonwoven fabric has better permeability and less backflow. Specifically, when there is a better fiber structure, compared with the existing fiber structure at the same basis weight, a greater thickness (0.55 mm) does not lead to a decrease in permeation speed, but rather an increase in permeation speed (less than 1.31 s) and a decrease in backflow (less than 151 mg).

[0081] In one exemplary embodiment, the infiltration rate is faster (≤1.3s) when the bulk density (0.2 kPa) is ≤3.9%.

[0082] In one exemplary embodiment, the bulk density (0.2 kPa) is ≤3.5%, and the infiltration rate is faster (≤1.25 s).

[0083] In one exemplary embodiment, the bulk density (1.4 kPa) is ≤7.3% and the reflow amount is low (≤133 mg).

[0084] In one exemplary embodiment, the bulk density (1.4 kPa) is ≤6.9%, and the amount of reflow is even less (≤106 mg). Attached Figure Description

[0085] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0086] Figure 1 The images show the appearance differences between the high-dryness nonwoven fabric of Embodiment D4 and the PE / PET hot-air nonwoven fabric of Comparative Example D1. Figure 1 The sample on the left is the appearance of Example D4; the sample on the right is the appearance of Comparative Example D1. The high dryness nonwoven fabric of the present invention has a richer capillary appearance, and has a higher liquid storage space and specific surface area.

[0087] Figure 2 A schematic diagram of the test method for core-sheath fiber eccentricity is shown; in the diagram, R represents the radius of the large circle, and d represents the distance between the centers of the large circle and the small circle.

[0088] Figure 3 The diagram shows the overflow zone generated by the nonwoven fabric of the absorbent product surface layer after being squeezed. 11 is the surface nonwoven fabric, and 12 is the absorbent core. Detailed Implementation

[0089] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0090] Therefore, the following detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0091] Terms and Explanations

[0092] "Absorbent products" refer to various daily necessities that are disposable after single use, come into direct or indirect contact with the human body, have the function of absorbing human excrement, and are used to achieve human physiological hygiene or health care purposes. Examples include: menstrual hygiene products for women and baby diapers.

[0093] Nonwoven fabric, also known as non-woven textile, is a sheet-like, web-like, or wadding-like material made by arranging fibers in a directional or random manner and then reinforcing them through friction, cohesion, bonding, or a combination of these methods. It is not formed through the traditional interlacing of warp and weft yarns, but rather by directly reinforcing the fiber web. Nonwoven materials produced using hot air bonding technology utilize hot air to heat the fiber web, causing the fiber surfaces to melt and bond together, thus forming a fluffy and soft structure with a certain strength. This type of nonwoven fabric is commonly referred to as hot air nonwoven fabric, and the nonwoven fabric of this invention belongs to the category of hot air nonwoven fabrics.

[0094] "Surface nonwoven fabric layer" refers to the outer layer or part of the outer layer in absorbent products, which serves to guide the body's excreted fluids to the absorbent core layer.

[0095] "Absorbent core" refers to the component in an absorbent product that has the largest absorption capacity for human excrement, including core encapsulation, absorbent material encapsulation, etc., and the absorbent material is exemplarily such as gel resin.

[0096] "Facing the human skin" refers to the relative position of a component or component surface, meaning that during wear or use, the component or component surface is closer to the wearer than some other components or component surfaces.

[0097] The core-sheath composite fiber disclosed in this invention

[0098] A core-sheath composite fiber, comprising a sheath and a core; the core material accounts for 20%-80% of the total mass of the core material, the base material of the sheath comprises polyethylene resin, the base material of the core material comprises polyester resin, and includes at least one of polybutylene terephthalate resin or polypropylene terephthalate resin.

[0099] In some embodiments of this application, the crimp angle of the core-sheath composite fiber is 65°-130°; preferably 90°-120°.

[0100] In some embodiments of this application, the number of crimps of the core-sheath composite fiber is 10-25mm to 25-25mm, preferably 12-24-25mm.

[0101] In some embodiments of this application, the dry heat shrinkage rate of the core-sheath composite fiber is 0.3%-7%; preferably 0.5-5%; and more preferably 0.5-2.2%.

[0102] In some embodiments of this application, the viscosity of the core material substrate is controlled between 0.8 dL / g and 1.3 dL / g.

[0103] In some embodiments of this application, the core material of the sheath-core composite fiber further includes a low-viscosity polyester resin, which is a similar polyester resin and has a viscosity of 0.5 dL / g-0.7 dL / g.

[0104] The amount of low-viscosity polyester resin in the total polyester resin should be controlled between 2wt% and 5wt%.

[0105] In some embodiments of this application, the fineness of the core-sheath composite fiber is 0.8 dtex-11 dtex; preferably 1-10 dtex.

[0106] In some embodiments of this application, the core-sheath composite fiber has a restricted eccentric structure, specifically d / R ≤ 33%; preferably d / R ≤ 15%; more preferably d / R ≤ 10%; and most preferably d / R ≤ 1%.

[0107] The preparation method of core-sheath composite fiber disclosed in this invention

[0108] A method for preparing a core-sheath composite fiber, comprising:

[0109] The core material is made of a polyester resin containing at least one or two of polybutylene terephthalate resin or polypropylene terephthalate resin, and the outer material is made of a polyethylene resin.

[0110] Core material and sheath material are spun to obtain core-sheath composite fiber nascent filaments; the core-sheath composite fiber nascent filaments are then subjected to post-stretching, crimping, and heat setting.

[0111] In some embodiments of this application, core material and sheath material are spun to obtain core-sheath composite fiber nascent filaments, including:

[0112] Select a spinneret with a concentric or eccentric structure for spinning targets, and control the spinning temperature at 250℃-275℃ and the spinning speed at 1000m / min-1500m / min.

[0113] In some embodiments of this application, post-stretching of the core-sheath composite fiber nascent filament includes:

[0114] When post-stretching the nascent filaments of the core-sheath composite fiber, the stretching ratio should be controlled to be 2-4 times, preferably 2.5-3.5 times.

[0115] In some embodiments of this application, crimping the core-sheath composite fiber nascent filament includes:

[0116] When crimping the nascent filaments of the core-sheath composite fiber, the crimping temperature should be controlled at 58℃-90℃ and the crimping pressure at 0.07-0.44MPa.

[0117] In some embodiments of this application, heat setting of the core-sheath composite fiber nascent filament includes:

[0118] When heat-setting the nascent filaments of the core-sheath composite fiber, the heat-setting temperature should be controlled at 110℃-125℃ and the drying time should be 5min-15min.

[0119] The high dryness nonwoven fabric disclosed in this invention

[0120] A nonwoven fabric comprising a core-sheath composite fiber, the core-sheath composite fiber including a sheath and a core; at least a portion of the sheath melts, causing the composite fiber sheath to be thermally bonded to each other to form bonding points; the core material of the core-sheath composite fiber accounts for 20%-80% by mass, the base material of the sheath includes polyethylene resin, the base material of the core material includes polyester resin, and includes at least one of polybutylene terephthalate resin or polypropylene terephthalate resin;

[0121] The bulk density (0.2 kPa) of nonwoven fabric is ≤3.9%.

[0122] The "non-woven fabric" in the above technical solution, when used as a surface layer or part of a surface layer in absorbent products, has good seepage speed and reverse seepage properties, and is referred to as a high-dryness non-woven fabric.

[0123] In the above technical solution, the base material of the sheath includes polyethylene resin (PE), and the base material of the core includes at least one of polybutylene terephthalate resin (PBT) or polypropylene terephthalate resin (PTT). To our knowledge, different sheath-core composite fibers exhibit different bulk densities of nonwoven fabrics with the same number of turns and crimp angle. This has not been discovered and utilized in nonwoven fabrics with high permeability and low rewetting. This invention is the first to propose applying nonwoven fabrics with specific fiber structures to the surface layer material of absorbent products. This type of nonwoven fabric with such bulk density properties has been found for the first time to be beneficial to human comfort as the surface layer of absorbent products. Currently, it has been found that when PBT or PTT is used as the core material of the sheath-core composite fiber, compared to traditional PET as the core material, the nonwoven fabric made from this base material has a superior structure, especially contributing to the bulk density (1.4 kPa) value.

[0124] Preferably, the bulk density (0.2 kPa) of the woven fabric is ≤3.5%.

[0125] The bulk density (0.2 kPa) of the nonwoven fabric is ≤3.9%, more preferably ≤3.5%; within this range, the nonwoven fabric has a faster seepage rate.

[0126] Absorbent sanitary products using this nonwoven fabric exhibit the following characteristics during use:

[0127] Hygiene absorbent products typically consist of an absorbent core and a wearable component. The absorbent core includes a non-woven fabric layer facing the skin, an absorbent core, and a waterproof membrane. Taking sanitary napkins as an example, the wearable component comprises the adhesive backing and release paper. For diapers, the wearable component includes the portion forming the waist opening and the portion forming the leg opening. When bodily fluids (such as urine) are expelled, they do not directly reach the absorbent core. Instead, they first seep into the non-woven fabric layer on the outer side of the absorbent core, closest to the skin, and are then absorbed by the liquid-absorbing polymer particles in the absorbent core. Bodily fluids need to quickly permeate through the non-woven fabric layer to the absorbent core. The faster the permeation, the shorter the time the liquid remains on the skin surface, resulting in greater comfort. Otherwise, it can cause skin discomfort or even allergies.

[0128] Experiments have shown that the infiltration rate is related to the bulk density of the nonwoven fabric layer (0.2 kPa). A lower bulk density results in larger gaps between fibers, leading to a larger infiltration rate and increasing the fluid flux per unit area.

[0129] As absorbent materials for hygiene products, the nonwoven fabric layer is required to be lightweight. Compared with the nonwoven fabric of the same weight in the prior art, the nonwoven fabric of the present invention exhibits superior absorption speed and reabsorption properties.

[0130] In some embodiments of this application, the bulk density (1.4 kPa) of the nonwoven fabric is ≤7.3%;

[0131] Preferably, the bulk density (1.4 kPa) of the nonwoven fabric is ≤6.9%.

[0132] Besides the infiltration rate, rewetting is also an important indicator for evaluating the comfort of absorbent products. The inventors discovered that the infiltration rate and rewetting of nonwoven fabrics are related to their internal structure. We use bulk density to characterize the internal structure of nonwoven fabrics, which represents the liquid storage space of the fiber network within the nonwoven fabric. As mentioned earlier, bulk density (0.2 kPa) affects the infiltration rate of the fluid, while the rewetting process is related to the bulk density of the nonwoven fabric layer (1.4 kPa). When absorbent products used for hygiene are subjected to body pressure after absorbing liquid, localized areas of the nonwoven fabric to the core are compressed, forming overflow zones of bodily fluids (such as...). Figure 3The diagram illustrates the overflow zone formed by the nonwoven fabric surface layer of an absorbent product after compression (11 is the surface nonwoven fabric, 12 is the absorbent core). In the overflow zone, bodily fluids seep back from the core and can be conducted to the fiber gaps in other uncompressed nonwoven fabric layers. A low bulk density (1.4 kPa) indicates that the gaps between fibers are preserved during compression, resulting in a strong liquid storage capacity of the nonwoven fabric layer. This stored liquid will further seep down until it is reabsorbed by the core. When the bulk density (1.4 kPa) is low, these seeping bodily fluids have more buffer time to be absorbed by the core, resulting in less liquid seeping back to the layer in contact with the body, keeping the nonwoven fabric side in contact with the body dry. A nonwoven fabric layer with an excessively high bulk density (1.4 kPa), when used as the surface layer of an absorbent product for hygiene purposes, will have poor liquid permeability, leading to increased backflow and a damp environment on the consumer's skin, thus affecting the user experience.

[0133] The bulk density (0.2 kPa) of the nonwoven fabric layer used in existing absorbent sanitary products is too high, especially under pressure, the bulk density (1.4 kPa) increases further, which is the root cause of the increased rewetting. Such products often give people a feeling of dampness on the skin contact surface, affecting the comfort of wearing them.

[0134] This invention discovers that when the bulk density (0.2 kPa) of the nonwoven fabric is controlled to be ≤3.9% and the bulk density (1.4 kPa) to be ≤7.3%, the infiltration rate of bodily fluids can be effectively increased, the reabsorption of absorbent products can be reduced, and a comfortable feeling can be provided even after prolonged wear. This allows absorbent products using this nonwoven fabric to exhibit higher softness to the touch and greater dryness during use.

[0135] In some embodiments of this application, the crimp angle of the core-sheath composite fiber is 65°-130°;

[0136] Preferably, the crimp angle of the core-sheath composite fiber is 90°-120°.

[0137] The crimp angle of the core-sheath composite fibers affects the fabric structure of the nonwoven fabric. As a preferred technical solution, the crimp angle of the core-sheath composite fibers is 65°-130°, which is beneficial to the fabric structure and bulk density. As a further preferred technical solution, the crimp angle of the core-sheath composite fibers is 90°-120°, which is even more beneficial to the fabric structure and further beneficial to reducing the bulk density.

[0138] In some embodiments of this application, the number of crimps in the core-sheath composite fiber is 10 crimps / 25mm to 25 crimps / 25mm;

[0139] Preferably, the number of crimps in the core-sheath composite fiber is 12-24 / 25mm.

[0140] The crimp number of the core-sheath composite fibers affects the microstructure of the nonwoven fabric. As a preferred technical solution, the crimp number of the core-sheath composite fibers is 10 crimps / 25mm to 25 crimps / 25mm; this is beneficial to the microstructure of the nonwoven fabric and helps to reduce its bulk density.

[0141] As a further preferred technical solution, the number of crimps of the core-sheath composite fiber is 12-24 / 25mm; this further benefits the nonwoven fabric's structure and reduces its bulk density.

[0142] In some embodiments of this application, the average thickness of the nonwoven fabric is >0.40 mm;

[0143] Preferably, the average thickness of the nonwoven fabric is ≥0.45mm, more preferably ≥0.50mm;

[0144] The weight of nonwoven fabric is 16 g / m² to 30 g / m².

[0145] The average thickness of the nonwoven fabric affects its liquid storage space and thus the permeation effect. In the above technical solution, the average thickness of the nonwoven fabric is greater than 0.40 mm, preferably at least 0.45 mm, which is beneficial for improving the infiltration rate and re-permeability, and thus improving the permeation effect of the nonwoven fabric. As a further preferred technical solution, the average thickness of the nonwoven fabric is ≥0.50 mm; this further improves the infiltration rate and re-permeability, and thus improves the permeation effect of the nonwoven fabric.

[0146] Nonwoven fabric layers in sanitary absorbent products typically require lightweight properties, meaning the basis weight of the nonwoven fabric cannot be too high. With the same fiber type, denier, and fiber structure, simply changing the thickness of the nonwoven fabric results in a higher basis weight for thicker fabrics. Therefore, we usually aim for a greater thickness at the same target basis weight (the target basis weight required by the customer). Customers generally control the basis weight of the nonwoven fabric to within 30 g / m² to ensure lightweight properties, but it should generally not be less than 16 g / m². Insufficient basis weight will lead to an excessively thin average thickness.

[0147] In some embodiments of this application, the dry heat shrinkage rate of the core-sheath composite fiber is 0.3%-7%;

[0148] When the fiber morphology is the same, but the dry heat shrinkage rate of the core-sheath composite fiber is different, the bulk density of the nonwoven fabric will change.

[0149] A lower dry heat shrinkage rate leads to a higher bulk density, decreased permeability and resistance to backflow, and reduced wearing comfort. On the other hand, the dry heat shrinkage rate of the fiber also affects its softness; it should be controlled between 0.3% and 7%. An excessively high rate results in a stiffer feel and increased bulk density. As a preferred technical solution, the dry heat shrinkage rate of the core-sheath composite fiber is 0.5%-5%, further improving permeability while maintaining softness.

[0150] Preferably, the dry heat shrinkage rate of the core-sheath composite fiber is 0.5-5%; more preferably, the dry heat shrinkage rate of the core-sheath composite fiber is 0.5-2.2%.

[0151] By further optimizing the range of dry heat shrinkage rate, the permeability of nonwoven fabrics can be further improved while maintaining softness.

[0152] In some embodiments of this application, the viscosity of the polyester resin is controlled between 0.8 dL / g and 1.3 dL / g.

[0153] The viscosity of polyester resin affects the dry heat shrinkage rate of core-sheath composite fibers; the higher the viscosity, the higher the dry heat shrinkage rate.

[0154] In the above technical solution, the viscosity of the polyester resin is controlled between 0.8 dL / g and 1.3 dL / g, which is beneficial for the core-sheath composite fiber to obtain a suitable dry heat shrinkage rate. The higher the shrinkage rate, the better the permeability.

[0155] In some embodiments of this application, the core material of the sheath-core composite fiber includes a low-viscosity polyester resin, which is a similar polyester resin and has a viscosity of 0.5 dL / g-0.7 dL / g.

[0156] The amount of low-viscosity polyester resin in the total polyester resin should be controlled between 2wt% and 5wt%.

[0157] Introducing low-viscosity components into polyester resin can adjust the slippage ability between resin molecular chains, giving it greater deformation ability to dissipate external forces when subjected to them, resulting in a softer feel.

[0158] In some embodiments of this application, the specific surface area of ​​the nonwoven fabric is ≥0.04m². 2 / g;

[0159] Preferably, the specific surface area of ​​the nonwoven fabric is ≥0.05m². 2 / g; further preferred specific surface area ≥0.07m² 2 / g, more preferably a specific surface area ≥0.08m² 2 / g, with an optimal specific surface area ≥0.11m² 2 / g.

[0160] The specific surface area of ​​nonwoven fabric can characterize the size of the specific surface area of ​​the fiber network within the nonwoven fabric.

[0161] Specific surface area is another important structural feature affecting rewetting. This is because, when there are fiber pores around the overflow zone, the specific surface area helps to quickly conduct the overflowing liquid to the fiber pores of other uncompressed nonwoven fabric layers. Liquid is conducted through the capillary effect of fibers. The higher the specific surface area, the larger the specific surface area of ​​the fibers. The rewetting liquid generated in the overflow zone will be quickly conducted to the adjacent uncompressed areas through the fiber specific surface area, making the rewetting of bodily fluids imperceptible to the human body. Research suggests that the higher the bulk density and the larger the specific surface area, the larger the area in contact with the liquid, thereby increasing the liquid conductivity of the nonwoven fabric, allowing the liquid to be absorbed more quickly and not remain on the surface of the nonwoven fabric, maintaining low rewetting of the material.

[0162] As a preferred technical solution, the specific surface area of ​​the nonwoven fabric is ≥0.07m². 2 / g can further improve permeability; further, a specific surface area ≥0.08m² is preferred. 2 / g, with an optimal specific surface area ≥0.11m² 2 / g.

[0163] In some embodiments of this application, the core-sheath composite fiber has a restricted eccentric structure, specifically d / R ≤ 33%; preferably d / R ≤ 15%; more preferably d / R ≤ 10%; and most preferably d / R ≤ 1%.

[0164] Further investigation revealed that when the core material in the core-sheath composite fiber has a restricted eccentric structure, the resulting nonwoven fabric exhibits a relatively more ideal microstructure. As a preferred technical solution, the core-sheath composite fiber has a d / R ratio ≤ 33%, more preferably d / R ≤ 15%, and even more preferably d / R ≤ 10%. When d / R ≤ 1%, the composite fiber essentially possesses a concentric structure (a concentric structure has a larger specific surface area), and 1% represents a reasonable error when spinning concentric fibers through concentric spinnerets.

[0165] It was found that using a restricted eccentric structure resulted in a better nonwoven fabric structure, specifically a larger specific surface area. A smaller d / R ratio resulted in a larger specific surface area of ​​the produced nonwoven fabric. This is inferred to be due to the increased bonding area caused by the eccentricity.

[0166] In some embodiments of this application, the fineness of the core-sheath composite fiber is 0.8 dtex-11 dtex; preferably 1 dtex-10 dtex.

[0167] The smaller the fineness, the better the softness and the higher the bulk density; conversely, the smaller the fineness, the worse the softness and the lower the bulk density. The smaller the fineness, the larger the specific surface area. However, when the bulk density becomes too large, the liquid storage capacity of the nonwoven fabric is greatly reduced. At this point, the increased conductivity of the fiber surface is insufficient to allow the large amount of re-seepage generated in the overflow area to be absorbed by the adjacent uncompressed areas. In this situation, the human body can easily perceive the re-seepage of bodily fluids.

[0168] In the above-mentioned technical solution, as a preferred technical solution, the fineness of the core-sheath composite fiber is 0.8 dtex-11 dtex; this is beneficial to the permeability and softness of the nonwoven fabric. As a further preferred technical solution, the fineness is 1 dtex-10 dtex, which further benefits the permeability and softness of the nonwoven fabric.

[0169] In some embodiments of this application, the melt index (170°C·2.16Kg) of the polyethylene resin is 7.8-18g / 10min.

[0170] Selecting a suitable melt index for polyethylene resin to be suitable for processing core-sheath nonwoven fabrics is a common practice for those skilled in the art; for example, 7.8-18 g / 10 min can be selected.

[0171] In some embodiments of this application, a nonwoven fabric is used in absorbent articles, wherein the nonwoven fabric is disposed in the absorbent core and on the side facing human skin.

[0172] In summary, the high-dryness nonwoven fabric of this application exhibits superior permeability under the same basis weight when the fiber structure differs, particularly when the bulk density (0.2 kPa) is less than or equal to 3.9% and the bulk density (1.4 kPa) is less than or equal to 7.3%. Specifically, when the fiber structure is superior, compared to nonwoven fabrics with existing fiber structures at the same basis weight, a greater thickness (0.55 mm) does not lead to a decrease in permeation rate; on the contrary, the permeation rate increases (less than 1.31 s), and the amount of rewetting decreases (less than 151 mg).

[0173] In one exemplary embodiment, the infiltration rate is faster (≤1.3s) when the bulk density (0.2 kPa) is ≤3.9%.

[0174] In one exemplary embodiment, the bulk density (0.2 kPa) is ≤3.5%, and the infiltration rate is faster (≤1.25 s).

[0175] In one exemplary embodiment, the bulk density (1.4 kPa) is ≤7.3% and the reflow amount is low (≤133 mg).

[0176] In one exemplary embodiment, the bulk density (1.4 kPa) is ≤6.9%, and the amount of reflow is even less (≤106 mg).

[0177] The high-dryness nonwoven fabric of this application, under the same basis weight and with an ideal bulk density, exhibits increased fiber surface area, which is more conducive to reducing the amount of rewetting in the nonwoven fabric. In particular, the specific surface area of ​​the fibers in the nonwoven fabric is ≥0.05m². 2 / g, preferably 0.07m 2 / g, more preferably ≥0.11m 2 / g.

[0178] The high dryness nonwoven fabric of this application has its structure affected by the core material composition, crimp angle and crimp number, and dry heat shrinkage rate of the core-sheath composite fiber. Appropriate crimp angle, crimp number, and dry heat shrinkage rate can yield a more favorable bulk density value for the nonwoven fabric. When a superior bulk density value is desired, at least one of PTT or PBT core material composition should be preferred, and one of the crimp angle, crimp number, and dry heat shrinkage rate should be optimized.

[0179] Preferably, the curling angle is 90°-120°. When the curling angle is selected as 90°-120°, better bulk density (0.2KPa) and bulk density (1.4KPa) values ​​can be obtained; when the curling angle is selected as 100°-110°, the bulk density (0.2KPa) and bulk density (1.4KPa) values ​​are optimal.

[0180] Preferably, the number of curls is selected as 12-24 (curls / 25mm). When the number of curls is selected as 12-24 (curls / 25mm), better bulk density (0.2KPa) and bulk density (1.4KPa) values ​​can be obtained; when the number of curls is selected as 12-19 (curls / 25mm), the bulk density (0.2KPa) and bulk density (1.4KPa) values ​​are optimal.

[0181] Preferably, the dry heat shrinkage rate is 0.3%-7%. When the dry heat shrinkage rate is selected to be 0.3%-7%, ideal bulk density (0.2 kPa) and bulk density (1.4 kPa) values ​​can be obtained. More preferably, the dry heat shrinkage rate is selected to be 0.5%-5%. Most preferably, the dry heat shrinkage rate is 0.5%-2.2%, which can balance improving the permeability and softness of the nonwoven fabric. Specifically, when the dry heat shrinkage rate is 0.5%-2.2%, the softness is 48 mN-49 mN.

[0182] In this application, the eccentric structure and fineness of the core-sheath composite fiber in the high-dryness nonwoven fabric affect the fabric's structure, specifically manifested as a change in specific surface area. A suitable eccentric structure and fineness can increase the specific surface area without affecting the bulk density.

[0183] The core-sheath composite fiber has a restricted eccentric structure, specifically d / R ≤ 33%; preferably d / R ≤ 15%; more preferably d / R ≤ 10%; and most preferably d / R ≤ 1%. The degree of restriction on eccentricity has been found to increase the specific surface area of ​​the internal structure of the nonwoven fabric.

[0184] When the d / R value is ≤1%, it is basically a concentric structure, which exhibits a better specific surface area compared to the biased structure.

[0185] The finer the fiber, the larger the specific surface area of ​​the fiber. However, finer fibers will also lead to a significant increase in bulk density. According to experiments, in general, after the fibers become finer, the decrease in bulk density has a significantly greater impact on the reduction of reverse osmosis performance than the contribution of the fiber specific surface area to the reduction of reverse osmosis performance. However, after the fibers become finer, the nonwoven fabric will become softer. Choosing a fiber fineness of 1dtex-10dtex is more conducive to balancing the permeability and softness of the nonwoven fabric.

[0186] The high-dryness nonwoven fabric of this application incorporates a low-viscosity polyester component with a viscosity of 0.5 dL / g to 0.7 dL / g into the polyester resin, which can improve the softness of the nonwoven fabric. The amount of this low-viscosity polyester component added can be selected from 2 wt% to 5 wt%.

[0187] The method for preparing high-dryness nonwoven fabric disclosed in this invention

[0188] A method for preparing a nonwoven fabric includes a fiber spinning process and a hot air process:

[0189] The fiber spinning process includes: using a polyester resin containing at least one or two of polybutylene terephthalate resin or polypropylene terephthalate resin as the core material; using a substrate containing polyethylene resin as the sheath material; spinning the core material and the sheath material to obtain core-sheath composite fiber filaments; and performing post-stretching, crimping, and heat setting on the core-sheath composite fiber filaments.

[0190] The hot air process includes: chopped fibers of the core-sheath composite fiber are combed and bonded with hot air to obtain nonwoven fabric.

[0191] In some embodiments of this application, core material and sheath material are spun to obtain core-sheath composite fiber nascent filaments, including:

[0192] Select a spinneret with a concentric or eccentric structure for spinning targets, and control the spinning temperature at 250℃-275℃ and the spinning speed at 1000m / min-1500m / min.

[0193] In some embodiments of this application, post-stretching of the core-sheath composite fiber nascent filament includes:

[0194] When post-stretching the nascent filaments of the core-sheath composite fiber, the stretching ratio should be controlled at 2-4 times; preferably 2.5-3.5 times.

[0195] If the stretch ratio is too low, the dry heat shrinkage rate will be too small; if the stretch ratio is too high, the dry heat shrinkage rate will be too large. As a preferred technical solution, controlling the stretch ratio between 2 and 4 times is beneficial for obtaining a suitable denier dry heat shrinkage rate and for reducing the bulk density of the nonwoven fabric. As a further preferred technical solution, the stretch ratio is preferably 2.5 to 3.5 times, which further helps to reduce the bulk density of the nonwoven fabric.

[0196] In some embodiments of this application, the core-sheath composite fiber nascent filament is crimped, including: when crimping the core-sheath composite fiber nascent filament, the crimping temperature is controlled at 58℃-90℃ and the crimping pressure is 0.07-0.44MPa.

[0197] The crimping process affects the control of the fiber crimping angle and crimp number. Too low a crimping temperature and too low a crimping pressure result in a larger crimping angle and fewer crimps; conversely, too high a crimping temperature and too high a crimping pressure result in a smaller crimping angle and more crimps. Controlling the crimping temperature to 58℃-90℃ and the crimping pressure to 0.07-0.44MPa is beneficial for adjusting the target crimping angle and crimp number.

[0198] In some embodiments of this application, heat setting of the nascent core-sheath composite fiber includes controlling the heat setting temperature to 110°C-125°C and the drying time to 5 min-15 min.

[0199] The heat setting process affects the dry heat shrinkage rate of fibers. If the heat setting temperature is too low or the time is too short, the dry heat shrinkage rate will be too high. If the heat setting temperature is too high or the time is too long, the dry heat shrinkage rate will be too low. Selecting a heat setting temperature of 110℃-125℃ and a drying time of 5min-15min is beneficial to adjusting the target dry heat shrinkage rate.

[0200] In some embodiments of this application, core-sheath composite fibers are selected as the fiber raw materials for nonwoven fabrics, and the initial processing state of the fibers is short fibers, including: the selected short fibers have a length of 38mm-51mm.

[0201] The length of short fibers can be adjusted to an exemplary range of 38-51 mm, but is not limited to this range. The appropriate fiber length for the nonwoven fabric preparation process is usually selected based on the actual equipment and raw material conditions. During the nonwoven fabric preparation process, in the fiber raw material preparation stage, fiber opening, mixing, and impurity removal are typically performed. These are routine preparatory steps to ensure the quality of the fiber web and will not be elaborated upon here. For more information, please refer to "Synthetic Leather Technology" edited by Qu Jianbo et al. to learn and master these routine operations.

[0202] In some embodiments of this application, the obtained core-sheath composite fibers are combed, including:

[0203] The cut short fibers are placed on a carding machine for carding and laid into a web. The carding machine cylinder speed is 50-65 Hz, the doffer speed is 30-47 Hz, and the target basis weight of the fiber web is controlled to be 11-21 g / m².

[0204] This process affects the thickness and bulk density of the nonwoven fabric. First, the initial thickness of the fiber web is controlled by adjusting the target basis weight, which in turn affects the final thickness of the nonwoven fabric. Different equipment uses methods to control the basis weight of the fiber web, which is common knowledge for those skilled in the art. For example, the basis weight is adjusted by coordinating the carding machine's feed roller speed (25-45 Hz) and output line speed (38-58 m / min). If the carding machine's feed roller speed is too slow or the carding machine's output line speed is too fast, the basis weight will be too low, resulting in a too-low thickness. Different equipment has varying degrees of automation, which will not be elaborated upon here. Second, the core influencing factors of the carding process are the control of the cylinder roller speed of the carding system and the doffer roller speed of the output system. This ensures that the carding process does not damage the fiber morphology. If the speed of the cylinder and doffer rollers is too fast, the fiber morphology is easily damaged. If the speed of the working rollers is too slow, fly waste, i.e., fibers that escape, is easily generated.

[0205] In some embodiments of this application, the prepared core-sheath composite fibers are hot-air bonded, including:

[0206] The combed short fibers are processed at a temperature of 130-150℃ and a blower frequency of 35-55HZ for 3-20 seconds to bond them into a nonwoven fabric.

[0207] Preferably, the processing temperature is 130-145℃;

[0208] Preferably, the blower frequency is 35-45 Hz;

[0209] Preferably, the processing time is 3-10 seconds.

[0210] The temperature of the hot air and the frequency of the blower affect the bonding and morphology of the fiber web, while the processing linear speed affects the residence time of the fiber web under the hot air temperature and blower frequency. For example, in an embodiment of the present invention, the residence time of the fiber web under the given temperature and air pressure conditions is controlled by controlling the linear speed. An exemplary control linear speed is 70-100 m / min, the residence time is approximately 3-20 seconds, the processing oven temperature is 130-150°C, and the blower frequency is controlled at 35-55 Hz. However, this process is not limited to this; those skilled in the art can adjust the hot air temperature and blower frequency according to different equipment operating conditions to ensure that the nonwoven fabric made from the fiber web of S7 has the target bulk density and strength.

[0211] Under suitable temperature and pressure conditions, the PE on the surface of the bicomponent fibers melts and, under pressure, forms entanglements between the fibers. Excessive temperature and / or pressure results in excessive surface bonding between fibers, leading to increased bulk density, decreased thickness, and reduced specific surface area of ​​the fibers in the nonwoven fabric. Conversely, insufficient temperature and / or inadequate pressure result in ineffective hot air bonding, leading to insufficient strength in the nonwoven fabric.

[0212] Absorbent article disclosed in this invention

[0213] An absorbent article, wherein the nonwoven fabric layer on the side of the absorbent article facing the human skin relative to the absorbent core is the nonwoven fabric provided in any of the foregoing embodiments; or, the nonwoven fabric layer on the side of the absorbent article facing the human skin relative to the absorbent core is a nonwoven fabric prepared by the method for preparing the nonwoven fabric provided in any of the foregoing embodiments.

[0214] Optionally, the surface nonwoven fabric in the absorbent article is the nonwoven fabric provided in any of the foregoing embodiments;

[0215] Optionally, the surface nonwoven fabric in the absorbent article is a nonwoven fabric prepared by the nonwoven fabric preparation method provided in any of the foregoing embodiments.

[0216] In some embodiments of this application, the absorbent articles include any one of: feminine hygiene products, panty liners, diapers, pull-up diapers, nursing pads, or diaper pads.

[0217] The test methods for each parameter in this application are as follows:

[0218] Determination of fiber crimp number and crimp angle in nonwoven fabrics

[0219] Take 20 fiber samples and make the actual length of the fibers greater than 25mm in a relaxed state. Measure and count the average length, and record it as the natural length a.

[0220] Use fiber clamps to hold each fiber and suspend it on the top balance arm of the crimping machine. Then use tweezers to place the other end of the fiber in the lower clamp. After applying a light load (0.0018cN / dtex) to balance, record the reading L1 (mm). Read the total number of crimp peaks and crimp valleys Ja, calculate the average value, and the number of crimps s = Ja × 12.5 / L1.

[0221] For each fiber sample, the average fiber length at an initial tension of 0.075 cN is denoted as L2 (mm), and the curling angle is 2×arcsin(a / L2).

[0222] 1. Determination of the fineness of core-sheath composite fibers

[0223] Fiber fineness was determined according to GB / T14335-2008 "Test Method for Linear Density of Short Chemical Fibers".

[0224] 2. Determination of specific surface area of ​​nonwoven fabrics

[0225] The specific surface area of ​​the sample was measured using the BET multi-point method, with nitrogen as the adsorbate. In this embodiment of the invention, the measuring instrument used was a BSD-PM2 physical adsorption analyzer from Best Instruments, and the detection values ​​were obtained using instrument data processing and analysis software (version Ver24.10.9). Before injection, the sample was pretreated at 100°C to remove water and impurity gases originally adsorbed on the sample surface for 12 hours.

[0226] The instrument data processing and analysis used the BET multi-point method (P / P0=0.0000-0.1984) specific surface area formula to obtain the detection value.

[0227]

[0228] 3. Average thickness

[0229] The average thickness of the nonwoven fabric was tested according to the method specified in GB / T24218.2-2009 "Textiles - Test Methods - Part 2: Determination of Thickness", with a test pressure of 0.2 kPa. The measured value was recorded as H, and the unit was cm.

[0230] 4. Determination of bulk density

[0231] The bulk density of nonwoven fabric is defined as the theoretical value of fiber volume divided by the volume of nonwoven fabric × 100%.

[0232] The nonwoven fabric sample was cut into 1 square meter pieces, and the weight of the nonwoven fabric was measured.

[0233] Theoretical fiber volume (cm) 3 = Weight of nonwoven fabric (g) / Total density of polymer (g / cm³) 3 );

[0234] Total density of polymer (g / cm³) 3 = Density of the core polymer in the core-sheath composite fiber (g / cm³) 3 ) × Core material mass percentage (%) + Density of core-sheath composite fiber polymer (g / cm³) 3 The contribution of the core polymer to the total polymer density is calculated as (%) × the mass percentage of the leather material. When the core polymer is a mixture, the contribution is also calculated as the material density × the mass percentage of that material. The density of PTT, PBT, and PET is calculated as 1.35 g / cm³. 3 Theoretically, the density of HDPE is 0.95 g / cm³. 3 Theoretical value.

[0235] The average thickness of the nonwoven fabric was determined according to the method of GB / T24218.2-2009, with a test pressure of 0.2 kPa. The average thickness of the nonwoven fabric sample measured under this condition is recorded as H (cm).

[0236] The average thickness of the nonwoven fabric was determined according to the method of GB / T24218.2-2009, with a test pressure of 1.4 kPa. The average thickness of the nonwoven fabric sample measured under this condition was recorded as Hp (cm).

[0237] Volume of nonwoven fabric (cm) 3 ) = 1 × 10 4 × Average height of the nonwoven fabric sample (cm).

[0238] Bulk density (0.2 kPa) = Theoretical fiber volume / (1 × 10⁻⁶ kPa) 4 ×H)×100%;

[0239] Bulk density (1.4 kPa) = Theoretical fiber volume / (1 × 10⁻⁶ kPa) 4 ×Hp)×100%.

[0240] 5. Polyester resin viscosity

[0241] The viscosity mentioned in this patent refers to intrinsic viscosity, which is tested according to the method specified in GB / T14190-2008 "Test Methods for Fiber Grade Polyester Chips (PET)". The solvent used is 50wt% phenol + 50wt% tetrachloromethane, and the test temperature is 25℃.

[0242] 6. Determination of Melt Flow Index

[0243] The MFR melt index of the resin was determined according to GB / T3682.1-2018, "Determination of melt mass flow rate (MFR) and melt volumetric flow rate (MVR) of thermoplastics - Part 1: Standard method", with test conditions of 170℃ and 2.16 kg.

[0244] 7. Dry heat shrinkage rate of fibers

[0245] The dry heat shrinkage rate of the sample was determined according to the method of FZ / T50004-2011 "Test Method for Dry Heat Shrinkage Rate of Polyester Staple Fiber". The initial load was 0.45 mN / dtex, and the dry heat treatment was carried out at 120℃ for 15 minutes.

[0246] 8. The softness of non-woven fabrics

[0247] The softness of nonwoven fabrics was determined using a softness tester. Samples of the hot-air nonwoven fabric, measuring 100mm × 100mm, were cut, with a dimensional deviation not exceeding ±0.5mm. The longitudinal and transverse directions of the samples were clearly marked. A slit width of 6.35mm was selected. The sample was placed symmetrically in the center of the instrument's test platform. The test was started by pressing the "Start Test" button. After the plate probe A completed the entire instrument's path, the instrument recorded the measured value. The result was calculated as the arithmetic mean of the longitudinal and transverse test results, expressed in mN and rounded to the nearest integer.

[0248] The method described in GB / T8942-2016, "Determination of Paper Softness," can be used for testing. The smaller the value measured for the sample, the softer the nonwoven fabric.

[0249] 9. Infiltration rate

[0250] Sample preparation: Cut a nonwoven fabric sample with a size of 125mm x 125mm for later use; prepare 0.9% physiological saline for later use; select qualitative filter paper (80±4gsm, filtration time 35-70s (filtration time for 10ml of 23±1℃ distilled water with a 10cm² area)).

[0251] The infiltration rate was measured using a liquid penetration meter. The specific procedure was as follows: Five sheets of filter paper (glossy side up) were stacked together and placed flat on the base plate of the liquid penetration meter. A non-woven fabric sample (glossy side up) was placed directly on top of the filter paper. The penetration plate of the liquid penetration meter was then placed directly on top of the filter paper, ensuring that the three elements were symmetrically centered on the funnel tip of the meter. The tip height was adjusted so that it was 5 mm above the circular cavity of the penetration plate. 5 ml of physiological saline was added to the funnel, and the timer was pressed to start the measurement. The value measured by the liquid penetration meter was the infiltration rate of the non-woven fabric. The second value obtained by the liquid penetration meter represents the infiltration rate; the shorter the second value, the faster the infiltration rate.

[0252] 10. Recirculation rate

[0253] Sample preparation: Cut a 125mm x 125mm nonwoven fabric sample for later use; prepare 0.9% physiological saline solution for later use; select qualitative filter paper (80±4gsm, filtration time 35-70s (filtering time for 10ml of 23±1℃ distilled water with a 10cm² area); select filter paper with a diameter of 11cm, wet strength ≥140mm water column (measured using a Hertzberg apparatus), and grayness <0.15%).

[0254] Ten layers of filter paper are placed on a flat surface. A nonwoven fabric sample is placed on the filter paper, and 10 ml of physiological saline is injected into the surface of the nonwoven fabric. The sample is allowed to stand for 1 minute to allow the saline to be fully absorbed. Then, five layers of filter paper (weight denoted as m1) are placed on the sample, and a 2.5 kg weight is quickly (within 5 seconds) and gently pressed onto the sample. Timing is restarted. After 2 minutes, the weight is removed, and the weight of the five layers of filter paper on the sample is recorded as m2. The rewetting amount M = m2 - m1. The rewetting amount of the nonwoven fabric is determined using the above method. A higher rewetting amount indicates poorer absorbency and comfort of the nonwoven fabric.

[0255] 11. Eccentricity

[0256] Reference Figure 2 The eccentricity of core-sheath composite fibers is defined as: eccentricity = d / R;

[0257] Where d represents the distance between the center of the core-sheath composite fiber and the center of the core material;

[0258] R represents the radius of the core-sheath composite fiber;

[0259] During measurement, the morphology of the fiber cross-section is collected using an electron microscope. Ten sets of fiber cross-sections are randomly selected. The Nikon Polarizing Microscope ECLIPSELV100POL system software can be used to mark the center of the core-sheath composite fiber and the center of the core material. Alternatively, the center can be marked manually. The d-value and R-value are calculated. When d / R ≤ 1%, it is a concentric structure. 1% is a common measurement error.

[0260] In this application, the terms "curl angle" and "curl number" of the fiber have meanings known in the art and can be adjusted to the target range using methods commonly used in the art. For example, the curl angle and curl number of the fiber are changed by adjusting preparation process parameters such as curl temperature and curl pressure. Generally, a lower curl temperature and lower curl pressure result in a larger curl angle and fewer curls; a higher curl temperature and higher curl pressure result in a smaller curl angle and more curls.

[0261] In this application, the "average thickness" of the nonwoven fabric has a meaning known in the art and can be adjusted to a target range using methods commonly found in the art. For example, the average thickness of the nonwoven fabric can be changed by adjusting manufacturing process parameters such as the basis weight of the nonwoven fabric and the target basis weight of the fiber web. Generally, the higher the basis weight of the nonwoven fabric, the higher its average thickness.

[0262] In this application, the term "dry heat shrinkage rate" of the fiber has a well-known meaning in the art and can be adjusted to a target range using methods commonly found in the art. For example, the dry heat shrinkage rate of the core-sheath composite fiber can be altered by adjusting raw material and preparation process parameters such as the viscosity of the polyester resin, heat setting temperature and time, and stretch ratio.

[0263] In this application, the term "eccentric structure d / R" of the fiber has a well-known meaning in the art and can be adjusted to the target range using methods commonly found in the art. For example, the eccentric structure d / R of the fiber to be spun is controlled by selecting a spinneret that produces a target concentric or eccentric structure.

[0264] In this application, the term "fineness" of a fiber has a meaning known in the art and can be adjusted to a target range using methods commonly found in the art. For example, the fineness of the fiber to be spun is controlled by adjusting the flow rate of the spinning melt metering pump.

[0265] In this application, "stretch ratio" has a meaning known in the art and can be adjusted to the target range using common methods in the art. For example, an appropriate stretching temperature and stretching roller speed can be selected so that the fiber can achieve a stretch of 2.5-3.5 times. The selection of stretching temperature and roller speed should be based on fiber characteristics, which is a conventional adjustment process for those skilled in the art. For example, the stretching temperature can be set to 45-85°C, and the stretching roller speed can be 105-135 m / min.

[0266] In this application, the term "dwell time" in the hot air bonding process has a well-known meaning in the art and can be adjusted to a target range using common methods in the art. For example, the dwell time of the fiber web under the given temperature and air pressure conditions can be controlled by controlling the linear speed; this is a common method for adjusting dwell time in the art. For example, in an embodiment of the present invention, the controlled linear speed is 70-100 m / min, and the specific range of the linear speed depends on the actual conditions.

[0267] Example

[0268] Regarding the selection of the leather material: PE is a conventional leather material component used for the core fiber of hot-air nonwoven fabrics. The appropriate melt index can usually be selected according to the processing conditions. The generally applicable melt index range is 6-20 g / 10 min. In this example, the leather material raw material is PE. The PE resin used in Example A1 is PE resin of grade 2911H from Zhenhai Refining & Chemical Co., Ltd., with a melt index of 14.6 g / 10 min (170℃·2.16Kg).

[0269] The PE resin used in Example A2 was PE resin of grade 2911FS from Fushun Petrochemical Company, with a melt index of 7.8 g / 10 min (170℃·2.16Kg).

[0270] The PE resin used in Example A3 was PE resin of grade 2911 from Fushun Petrochemical Company, with a melt index of 18 g / 10 min (170℃·2.16Kg).

[0271] The selection of raw material PE is conventional technical knowledge in the field of hot air nonwoven fabric preparation. The above information is only an exemplary representation of the raw material details of a specific embodiment and does not have a limiting effect on the present invention.

[0272] Example A: Core-Sheath Composite Fiber Spinning Process

[0273] A process for spinning core-sheath composite fibers is provided, which is prepared according to the following steps S1-S5.

[0274] Example A1

[0275] S1: Raw material preparation: The raw material for the lining is PE resin; the raw material for the core is PTT resin; the viscosity of the core resin is controlled at 0.8 dL / g. In the lining-core composite fiber, the core material accounts for 50% of the total mass.

[0276] S2: Core-sheath composite spinning: Using the raw materials prepared in step S1, a spinneret with a core-sheath structure is selected, and spinning is carried out at a spinning temperature of 250℃ and a spinning speed of 1000m / min to obtain the nascent filament of core-sheath composite fiber.

[0277] S3: Post-stretching process: The nascent yarn obtained in step S2 is post-stretched; the stretching ratio is 2.5 times.

[0278] S4: Crimping process: The post-stretched fibers obtained in step S3 are crimped; the crimping temperature is 70℃ and the crimping pressure is 0.14MPa.

[0279] S5: Heat setting process: The crimped fibers obtained in step S4 are heat-set to obtain core-sheath composite fibers; the heat setting temperature is 115℃, and the drying time is 5 minutes. The core-sheath composite fibers of the present invention refer to fibers of any length, and those suitable for preparing nonwoven fabrics are generally short fibers. The present invention does not limit the fiber cutting to be carried out simultaneously on the spinning production line and then packaged, or to the fibers packaged in filament rolls being cut separately in an offline process.

[0280] Example A2

[0281] S1: Raw material preparation: The raw material for the lining is PE resin; the raw material for the core is PTT resin; the viscosity of the core resin is controlled at 1 dL / g. In the lining-core composite fiber, the core material accounts for 20% of the total mass.

[0282] S2: Core-sheath composite spinning: Using the raw materials prepared in step S1, a spinneret with a target eccentric structure is selected, and spinning is carried out at a spinning temperature of 275℃ and a spinning speed of 1500m / min to obtain the nascent filament of core-sheath composite fiber.

[0283] S3: Post-stretching process: The nascent yarn obtained in step S2 is post-stretched; the stretching ratio is 3.5 times.

[0284] S4: Crimping process: The post-stretched fibers obtained in step S3 are crimped; the crimping temperature is 90℃ and the crimping pressure is 0.3MPa.

[0285] S5: Heat setting process: The crimped fibers obtained in step S4 are heat-set to obtain core-sheath composite fibers; the heat setting temperature is 125℃, and the drying time is 10 minutes. The core-sheath composite fibers of this invention refer to fibers of any length, and those suitable for preparing nonwoven fabrics are generally short fibers. This invention does not limit the fiber cutting to be carried out simultaneously on the spinning production line and then packaged, or to the fibers packaged in filament rolls being cut separately in an offline process.

[0286] Example A3

[0287] S1: Raw material preparation: The raw material for the lining is PE resin; the raw material for the core is PTT resin; the viscosity of the core resin is controlled at 1.3 dL / g. In the lining-core composite fiber, the core material accounts for 80% of the total mass.

[0288] S2: Core-sheath composite spinning: Using the raw materials prepared in step S1, a spinneret with a target eccentric structure is selected, and spinning is carried out at a spinning temperature of 260℃ and a spinning speed of 1200m / min to obtain the nascent filament of core-sheath composite fiber.

[0289] S3: Post-stretching process: The nascent yarn obtained in step S2 is post-stretched; the stretching ratio is 3 times.

[0290] S4: Crimping process: The post-stretched fibers obtained in step S3 are crimped; the crimping temperature is 80℃ and the crimping pressure is 0.4MPa.

[0291] S5: Heat setting process: The crimped fibers obtained in step S4 are heat-set to obtain core-sheath composite fibers; the heat setting temperature is 120℃, and the drying time is 15min. The core-sheath composite fibers of the present invention refer to fibers of any length, and those suitable for preparing nonwoven fabrics are generally short fibers. The present invention does not limit the fiber cutting to be carried out simultaneously on the spinning production line and then packaged, or to the fibers packaged in filament rolls being cut separately in an offline process.

[0292] Example A4

[0293] The process differs from that of Example A1 in that the core material is PBT resin; the curling temperature is 80°C and the heat setting temperature is 120°C.

[0294] Comparative Example A1

[0295] The process differs from that of Example A1 in that the core material is PET resin; the curling temperature is 80°C and the heat setting temperature is 150°C.

[0296] Example A5

[0297] The process is basically the same as that of Example A1, except that the curling temperature is 80°C and the curling pressure is 0.09 MPa. This process adjustment makes the curling angle of the fiber obtained in Example A1 different from that in Example A1.

[0298] Example A6

[0299] The process is basically the same as that of Example A1, except that the curling temperature is 65°C and the curling pressure is 0.16 MPa. This process adjustment makes the curling angle of the fiber obtained in Example A1 different from that in Example A1.

[0300] Example A7

[0301] The process is basically the same as that of Example A1, except that the curling temperature is 62°C and the curling pressure is 0.19 MPa. This process adjustment makes the curling angle of the fiber obtained in Example A1 different from that in Example A1.

[0302] Example A8

[0303] The process is basically the same as that of Example A1, except that the curling temperature is 60°C and the curling pressure is 0.21 MPa. This process adjustment makes the curling angle of the fiber obtained in Example A1 different from that in Example A1.

[0304] Example A9

[0305] The process is basically the same as that of Example A1, except that the curling temperature is 58°C and the curling pressure is 0.23 MPa. This process adjustment makes the curling angle of the fiber obtained in Example A1 different from that in Example A1.

[0306] Example A10

[0307] The process is basically the same as that of Example A1, except that the curling temperature is 73°C and the curling pressure is 0.07 MPa. This process adjustment makes the number of fiber curls different from that of Example A1.

[0308] Example A11

[0309] The process is basically the same as that of Example A1, except that the curling temperature is 72°C and the curling pressure is 0.1 MPa. This process adjustment makes the number of fiber curls different from that of Example A1.

[0310] Example A12

[0311] The process is basically the same as that of Example A1, except that the curling temperature is 71°C and the curling pressure is 0.11 MPa. This process adjustment makes the number of fiber curls different from that of Example A1.

[0312] Example A13

[0313] The process is basically the same as that of Example A1, except that the curling temperature is 69°C and the curling pressure is 0.35 MPa. This process adjustment makes the number of fiber curls different from that of Example A1.

[0314] Example A14

[0315] The process is basically the same as that of Example A1, except that the curling temperature is 62°C and the curling pressure is 0.44 MPa. This process adjustment makes the number of fiber curls different from that of Example A1.

[0316] Example A15

[0317] The process is basically the same as that of Example A1, except that the stretching ratio is 2 times and the heat setting temperature is 125°C. This process adjustment makes the dry heat shrinkage rate of the fiber obtained in Example A1 different from that in Example A1.

[0318] Example A16

[0319] The process is basically the same as that of Example A1, except that the stretching ratio is 3 times. This process adjustment makes the dry heat shrinkage rate of the fiber obtained in Example A1 different from that in Example A1.

[0320] Example A17

[0321] The process is basically the same as that of Example A1, except that the stretching ratio is 4 times and the heat setting temperature is 110°C. This process adjustment makes the dry heat shrinkage rate of the fiber obtained in Example A1 different from that in Example A1.

[0322] Example A18

[0323] The process is basically the same as that of Example A1, except that the viscosity of the core material substrate is 0.6 dL / g. This process adjustment makes the dry heat shrinkage rate of the fiber obtained in Example A1 different from that in Example A1.

[0324] Example A19

[0325] The difference from Example A1 is that a low-viscosity polyester resin is also added to the core material; wherein, the viscosity of the low-viscosity polyester resin is 0.5 dL / g; and the low-viscosity polyester resin accounts for 2 wt% of the total polyester resin.

[0326] Example A20

[0327] The difference from Example A1 is that a low-viscosity polyester resin is also added to the core material; wherein, the viscosity of the low-viscosity polyester resin is 0.7 dL / g; and the low-viscosity polyester resin accounts for 5 wt% of the total polyester resin.

[0328] Example A21

[0329] The difference between the core-sheath composite fiber in Example A1 is that a spinneret with an eccentricity d / R of about 10% is selected for spinning to produce a core-sheath composite fiber with an eccentric structure.

[0330] Example A22

[0331] The difference between the core-sheath composite fiber in Example A1 is that a spinneret with an eccentricity d / R of about 15% is selected for spinning to produce a core-sheath composite fiber with an eccentric structure.

[0332] Example A23

[0333] The difference from the core-sheath composite fiber in Example A2 is that the fineness of the final core-sheath composite fiber is controlled to be 0.8 dtex by adjusting the flow rate of the spinning melt metering pump.

[0334] Example A24

[0335] The difference from the core-sheath composite fiber in Example A3 is that the fineness of the final core-sheath composite fiber is controlled to be 11 dtex by adjusting the flow rate of the spinning melt metering pump.

[0336] Example B: Core-Sheath Composite Fiber

[0337] A core-sheath composite fiber is provided, which are products obtained by the preparation processes of Examples A1-A24, respectively.

[0338] Example B1

[0339] The core-sheath composite fiber has a PE resin sheath and a PTT resin with a viscosity of 0.8 dL / g as the core material; the core material accounts for 50% of the fiber's mass. The fiber has a crimp angle of 90° and a crimp count of 19 crimps per 25 mm. The dry heat shrinkage rate is 0.5%. The fineness of the obtained core-sheath composite fiber is 5 dtex. The obtained core-sheath composite fiber has a d / R ratio ≤ 1% (measured value 0.8%) and exhibits a concentric core structure.

[0340] Example B2

[0341] The core-sheath composite fiber has a PE resin sheath and a PTT resin with a viscosity of 1 dL / g as the core material; the core material accounts for 20% of the fiber's mass. The fiber has a crimp angle of 120° and a crimp count of 14 crimps per 25 mm. The dry heat shrinkage rate is 5%. The fineness of the obtained core-sheath composite fiber is 1 dtex. The d / R ratio of the obtained core-sheath composite fiber is 5%, indicating an off-core structure.

[0342] Example B3

[0343] The core-sheath composite fiber has a PE resin sheath and a PTT resin with a viscosity of 1.3 dL / g as the core material; the core material accounts for 80% of the fiber's mass. The fiber has a crimp angle of 100° and a crimp count of 23 crimps per 25 mm. The dry heat shrinkage rate is 2%. The fineness of the obtained core-sheath composite fiber is 10 dtex. The d / R ratio of the obtained core-sheath composite fiber is 33%, exhibiting an off-core structure.

[0344] Example B4

[0345] The composition, shape, and size of the core-sheath composite fiber are similar to those in Example B1, the only difference being that the core material is PBT resin.

[0346] Comparative Example B1

[0347] The composition, shape, and size of the core-sheath composite fiber are similar to those of Example B1, the only difference being that the core material is PET resin.

[0348] Example B5

[0349] The composition, shape, and size of the core-sheath composite fiber are similar to those of Example B1. The only difference is that the fiber crimp angle is 65° and the number of fiber crimps is controlled to be consistent with that of B1.

[0350] Example B6

[0351] The composition, shape, and size of the core-sheath composite fiber are similar to those of Example B1. The only difference is that the fiber crimp angle is 100° and the number of fiber crimps is controlled to be consistent with that of B1.

[0352] Example B7

[0353] The composition, shape, and size of the core-sheath composite fiber are similar to those of Example B1. The only difference is that the fiber crimp angle is 110° and the number of fiber crimps is controlled to be consistent with that of B1.

[0354] Example B8

[0355] The composition, shape, and size of the core-sheath composite fiber are similar to those of Example B1. The only difference is that the fiber crimp angle is 120° and the number of fiber crimps is controlled to be consistent with that of B1.

[0356] Example B9

[0357] The composition, shape, and size of the core-sheath composite fiber are similar to those of Example B1. The only difference is that the fiber crimp angle is 130° and the number of fiber crimps is controlled to be consistent with that of B1.

[0358] Example B10

[0359] The composition, shape, and size of the core-sheath composite fiber are similar to those of Example B1. The only difference is that the number of fiber crimps is 10 / 25mm, and the fiber crimp angle is controlled in the same way as in B1.

[0360] Example B11

[0361] The composition, shape, and size of the core-sheath composite fiber are similar to those of Example B1. The only difference is that the number of fiber crimps is 12 / 25mm, and the fiber crimp angle is controlled in the same way as in B1.

[0362] Example B12

[0363] The composition, shape, and size of the core-sheath composite fiber are similar to those of Example B1. The only difference is that the number of fiber crimps is 15 / 25mm, and the fiber crimp angle is controlled in the same way as in B1.

[0364] Example B13

[0365] The composition, shape, and size of the core-sheath composite fiber are similar to those of Example B1. The only difference is that the number of crimps in the fiber is 24 / 25mm, and the crimp angle of the fiber is controlled in the same way as in B1.

[0366] Example B14

[0367] The composition, shape, and size of the core-sheath composite fiber are similar to those of Example B1. The only difference is that the number of crimps in the fiber is 25 / 25mm, and the crimp angle of the fiber is controlled in the same way as in B1.

[0368] Example B15

[0369] The composition, shape, and size of the core-sheath composite fiber are similar to those in Example B1, with the only difference being that the dry heat shrinkage rate of the fiber is 0.3%.

[0370] Example B16

[0371] The composition, shape, and size of the core-sheath composite fiber are similar to those in Example B1, with the only difference being that the dry heat shrinkage rate of the fiber is 2.2%.

[0372] Example B17

[0373] The composition, shape, and size of the core-sheath composite fiber are similar to those in Example B1, with the only difference being that the dry heat shrinkage rate of the fiber is 7%.

[0374] Example B18

[0375] The fiber composition, morphology, and size are similar to those of the core-sheath composite fiber in Example B1, except that the viscosity of the fiber core material is 0.6 dL / g and the dry heat shrinkage rate is 0.3%.

[0376] Example B19

[0377] The difference between this and the core-sheath composite fiber in Example B1 is that a low-viscosity polyester resin is added to the core material; wherein, the viscosity of the low-viscosity polyester resin is 0.5 dL / g; the low-viscosity polyester resin accounts for 2 wt% of the total polyester resin; the dry heat shrinkage rate is 0.46%, and the number of crimps is 20 / 25 mm.

[0378] Example B20

[0379] The difference between this and the core-sheath composite fiber in Example B1 is that a low-viscosity polyester resin is added to the core material; wherein, the viscosity of the low-viscosity polyester resin is 0.7 dL / g; the low-viscosity polyester resin accounts for 5 wt% of the total polyester resin; the dry heat shrinkage rate is 0.49%, and the number of crimps is 20 / 25 mm.

[0380] Example B21

[0381] The difference between the core-sheath composite fiber and Example B1 is that the core-sheath composite fiber obtained has a d / R of 10% and is an off-core structure.

[0382] Example B22

[0383] The difference between the core-sheath composite fiber and Example B1 is that the core-sheath composite fiber obtained has a d / R of 15% and is an off-core structure.

[0384] Example B23

[0385] The difference between the core-sheath composite fiber and the core-sheath composite fiber in Example B2 is that the fineness of the obtained core-sheath composite fiber is 0.8 dtex.

[0386] Example B24

[0387] The difference between the core-sheath composite fiber and Example B3 is that the fineness of the obtained core-sheath composite fiber is 11 dtex.

[0388] Example C: High-dryness nonwoven fabric spinning process

[0389] Example C1

[0390] A high-dryness nonwoven fabric spinning process is provided, which is prepared according to the following process: specifically including the spinning process of core-sheath composite fibers and the hot air process.

[0391] The core-sheath composite fiber spinning process of C1 is the same as that of A1, and the core-sheath composite fiber obtained by spinning is the same as that of B1; the core-sheath composite fiber of the above-mentioned core-sheath composite fiber is subjected to a hot air process, and the hot air process of C1 is set with the following parameters.

[0392] S1. Select the core-sheath composite fiber B1 as the fiber raw material for nonwoven fabric, and the initial processing state of the fiber is short fiber. Select the length of the fiber as 38mm.

[0393] S2. Fiber carding: The short fibers obtained in step S1 are placed on a carding machine for carding and laid into a web. The cylinder speed of the carding machine is 50 Hz and the doffer speed is 30 Hz. The target basis weight of the fiber web is controlled to be 14 g / m².

[0394] S3. Hot air bonding: The combed short fibers are processed at a temperature of 130℃ and a blower frequency of 35HZ for about 5 seconds to bond them into a high-dryness nonwoven fabric.

[0395] Example C2

[0396] A high-dryness nonwoven fabric spinning process is provided, which is prepared according to the following process: specifically including the spinning process of core-sheath composite fibers and the hot air process.

[0397] The core-sheath composite fiber spinning process of C2 is the same as that of A2, and the core-sheath composite fiber obtained is the same as that of B2; the core-sheath composite fiber of C2 is subjected to a hot air process, and the hot air process of C2 is set with the following parameters.

[0398] S1. Select the core-sheath composite fiber B2 as the fiber raw material for nonwoven fabric, and the initial processing state of the fiber is short fiber. Select the length of the fiber as 51mm.

[0399] S2. Fiber carding: The short fibers obtained in step S1 are placed on a carding machine for carding and laid into a web. The cylinder speed of the carding machine is 65 Hz and the doffer speed is 47 Hz. The target basis weight of the fiber web is controlled to be 17 g / m².

[0400] S3. Hot air bonding: The combed short fibers are treated at a temperature of 145℃ and a blower frequency of 45HZ for a processing window, with a dwell time of about 10 seconds, so that they are bonded into a high-dryness nonwoven fabric.

[0401] Example C3

[0402] A high-dryness nonwoven fabric spinning process is provided, which is prepared according to the following process: specifically including the spinning process of core-sheath composite fibers and the hot air process.

[0403] The core-sheath composite fiber spinning process of C3 is the same as that of A3, and the core-sheath composite fiber obtained is the same as that of B3; the core-sheath composite fiber is subjected to a hot air process, and the hot air process of C3 is set with the following parameters.

[0404] S1. Select the core-sheath composite fiber B3 as the fiber raw material for nonwoven fabric, and the initial processing state of the fiber is short fiber. Select the length of the fiber as 40mm.

[0405] S2. Fiber carding: The short fibers obtained in step S1 are placed on a carding machine for carding and laid into a web. The cylinder speed of the carding machine is 60 Hz and the doffer speed is 40 Hz. The target basis weight of the fiber web is controlled to be 15 g / m².

[0406] S3. Hot air bonding: The combed short fibers are processed at a temperature of 140℃ and a blower frequency of 40HZ for about 3 seconds to bond them into a high-dryness nonwoven fabric.

[0407] Example C4

[0408] The core-sheath composite fiber spinning process of Example C4 is the same as that of Example A4; the hot air process of Example C4 is the same as that of Example C1.

[0409] Comparative Example C1

[0410] The core-sheath composite fiber spinning process of Comparative Example C1 is the same as that of Comparative Example A1; the hot air process of Comparative Example C1 is the same as that of Example C1.

[0411] Examples C5-C22

[0412] The core-sheath composite fiber spinning process of Examples C5-C22 is the same as that of Examples A5-A22; the hot air process of Examples C5-C22 is the same as that of Example C1.

[0413] Example C23

[0414] The core-sheath composite fiber spinning process of Example C23 is the same as that of Example A23; the hot air process of Example C23 is the same as that of Example C2.

[0415] Example C24

[0416] The core-sheath composite fiber spinning process of Example C24 is the same as that of Example A24; the hot air process of Example C24 is the same as that of Example C3.

[0417] Example C25

[0418] The core-sheath composite fiber spinning process of Example C25 is the same as that of Example A1; the hot air process of Example C25 is basically the same as that of Example C1, the only difference being the short fiber processing temperature during the hot air bonding stage, which is 150°C.

[0419] Example C26

[0420] The core-sheath composite fiber spinning process of Example C26 is the same as that of Example A1; the hot air process of Example C26 is basically the same as that of Example C1, the only difference being the frequency of the blower for short fiber processing in the hot air bonding stage, which is 55HZ.

[0421] Example C27

[0422] The core-sheath composite fiber spinning process of Example C27 is the same as that of Example A1; the hot air process of Example C27 is basically the same as that of Example C1, except that the processing time of the hot air bonding stage is different, specifically 20 seconds.

[0423] Example C28

[0424] The core-sheath composite fiber spinning process of Example C28 is the same as that of Example A1; the hot air process of Example C28 is basically the same as that of Example C1, the only difference being the target basis weight of the fiber web, which is 11 g / m².

[0425] Example D: High-dryness nonwoven fabric spinning

[0426] A high-dryness nonwoven fabric is provided, which are products obtained by the preparation processes of Examples C1-C28 respectively.

[0427] The high-dryness nonwoven fabric is composed of a core-sheath composite fiber, in which at least part of the sheath material melts, causing the composite fiber sheath material to be thermally bonded to each other to form bonding points.

[0428] Example D1

[0429] The high-dryness nonwoven fabric has a core-sheath composite fiber with PE resin as the sheath material and PTT resin with a viscosity of 0.8 dL / g as the core material. The core material accounts for 50% of the total mass of the core-sheath composite fiber. The core-sheath composite fiber has a crimp angle of 90°, a crimp count of 19 crimps / 25mm, a dry heat shrinkage rate of 0.5%, a fineness of 5 dtex, and a core-sheath composite fiber d / R ≤ 1%, exhibiting a concentric core structure. The high-dryness nonwoven fabric has a bulk density (0.2 kPa) of 3.4% and a bulk density (1.4 kPa) of 6.9%. The average thickness H of the high-dryness nonwoven fabric is 0.51 mm. The basis weight of the high-dryness nonwoven fabric is 20 g / m². The specific surface area of ​​the high-dryness nonwoven fabric is 0.08 m². 2 / g.

[0430] The high dryness nonwoven fabric was measured to have a rewetting amount of 103 mg, a seepage rate of 1.24 s, and a softness (MD direction) of 49 mN.

[0431] Example D2

[0432] The high-dryness nonwoven fabric has a core-sheath composite fiber with PE resin as the sheath material and PTT resin with a viscosity of 1 dL / g as the core material. The core material accounts for 20% of the total mass of the core-sheath composite fiber. The core-sheath composite fiber has a crimp angle of 120°, a crimp count of 14 crimps / 25mm, a dry heat shrinkage rate of 5%, a fineness of 1 dtex, and a d / R ratio of 5%, exhibiting an off-core structure. The high-dryness nonwoven fabric has a bulk density (0.2 kPa) of 3.6% and a bulk density (1.4 kPa) of 7%. The average thickness H of the high-dryness nonwoven fabric is 0.67 mm, and the basis weight is 25 g / m².

[0433] The specific surface area of ​​the high-dryness nonwoven fabric was measured to be 0.11 m². 2 / g; reabsorption rate 105mg, infiltration rate 1.26s, softness (MD direction) 23mN.

[0434] Example D3

[0435] The high-dryness nonwoven fabric has a core-sheath composite fiber with PE resin as the sheath material and PTT resin with a viscosity of 1.3 dL / g as the core material. The core material accounts for 80% of the total mass of the core-sheath composite fiber. The core-sheath composite fiber has a crimp angle of 100°, a crimp count of 23 crimps / 25mm, a dry heat shrinkage rate of 2%, a fineness of 10 dtex, a d / R ratio of 33%, and an off-core structure. The high-dryness nonwoven fabric has a bulk density (0.2 kPa) of 3.3% and a bulk density (1.4 kPa) of 6.8%. The average thickness H of the high-dryness nonwoven fabric is 0.52 mm; the basis weight is 22 g / m²; and the specific surface area is 0.05 m². 2 / g.

[0436] The rewetting amount of the high dryness nonwoven fabric was measured to be 107 mg, the seepage rate was 1.23 s, and the softness (MD direction) was 66 mN.

[0437] I. The Influence of Core Material on Downflow and Reverse Osmosis Effects

[0438] Example D4

[0439] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the fiber used to make the high dryness nonwoven fabric in Example D4 is PBT resin as the core material, the bulk density (0.2kPa) of the high dryness nonwoven fabric is 3.7%; and the bulk density (1.4kPa) of the high dryness nonwoven fabric is 7.1%; the average thickness H of the high dryness nonwoven fabric is 0.47mm.

[0440] The high dryness nonwoven fabric was measured to have a rewetting amount of 113 mg, a seepage rate of 1.28 s, and a softness (MD direction) of 52 mN.

[0441] Comparative Example D1

[0442] The difference between Comparative Example D1 and Example D1 lies in the following components and structural parameters of the nonwoven fabric: the core material of the fiber constituting the nonwoven fabric in Comparative Example D1 is PET resin, the bulk density (0.2kPa) of the nonwoven fabric is 4.3%; and the bulk density (1.4kPa) of the nonwoven fabric is 7.6%; the average thickness H of the nonwoven fabric is 0.40mm.

[0443] The backwash rate of the comparative example D1 nonwoven fabric was measured to be 151 mg, the infiltration rate was 1.31 s, and the softness (MD direction) was 55 mN.

[0444] Examples 1, 4, and Comparative Example 1 are compared to explore the influence of material on the bulk density of nonwoven fabrics. In this set of examples and comparative examples, the bulk density of nonwoven fabrics was changed by adjusting the material of the core material in the core-sheath composite fiber. Generally, as the material of the core matrix changes, some preparation parameters in the fiber spinning process also change accordingly, such as the crimping pressure and heat setting temperature in this set of examples. Comparing Examples D1, D4, and Comparative Example D1, it can be seen that when PBT or PTT is used as the core material of the core-sheath composite fiber, the bulk density values ​​of Examples D1 and D4 are lower than those of traditional PET as the core material. Correspondingly, Examples D1 and D4 have lower backflow and faster seepage rates. Bulk density characterizes the internal structure of the nonwoven fabric, and this value represents the liquid storage space of the fiber network within the nonwoven fabric. Examples D1 and D4 have lower bulk density (0.2 kPa), indicating that when PBT or PTT is used as the core material of the core-sheath composite fiber, the nonwoven fabric has better liquid storage space and larger gaps between fibers, resulting in a faster infiltration rate. Examples D1 and D4 have lower bulk density (1.4 kPa), indicating that when PBT or PTT is used as the core material of the core-sheath composite fiber, the nonwoven fabric layer has strong liquid storage capacity under compression, resulting in a smaller rewetting amount. Therefore, when PBT or PTT is used as the core material, and the bulk density (0.2 kPa) is less than 4.3% and the bulk density (1.4 kPa) is less than 7.6%, the nonwoven fabric has better permeability, with an infiltration rate of less than 1.31 s and a rewetting amount of less than 151 mg.

[0445] Figure 1 The appearance differences between the high dryness nonwoven fabric of Embodiment D4 and the PE / PET hot air nonwoven fabric of Comparative Example D1 are shown in the figure. Figure 1 The sample on the left is the appearance of Example D4; the sample on the right is the appearance of Comparative Example D1. By comparison, it can be seen that the high dryness nonwoven fabric of the present invention has a richer capillary appearance, and has a higher liquid storage space and specific surface area.

[0446] II. The Influence of Fiber Morphology (Curl Angle, Number of Curls) on Infiltration and Reverse Osmosis Effects

[0447] Example D5

[0448] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the crimp angle of the fibers constituting the high dryness nonwoven fabric in Example D5 is 65°; the bulk density (0.2kPa) of the high dryness nonwoven fabric is 3.7%; and the bulk density (1.4kPa) of the high dryness nonwoven fabric is 7.2%; the average thickness H of the high dryness nonwoven fabric is 0.47mm.

[0449] The high dryness nonwoven fabric was measured to have a rewetting amount of 121 mg, a seepage rate of 1.28 s, and a softness (MD direction) of 47 mN.

[0450] Example D6

[0451] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the crimp angle of the fibers constituting the high dryness nonwoven fabric in Example D6 is 100°; the bulk density (0.2kPa) of the high dryness nonwoven fabric is 3.3%; and the bulk density (1.4kPa) of the high dryness nonwoven fabric is 6.7%; the average thickness H of the high dryness nonwoven fabric is 0.53mm.

[0452] The high dryness nonwoven fabric was measured to have a rewetting amount of 100 mg, a seepage rate of 1.21 s, and a softness (MD direction) of 49 mN.

[0453] Example D7

[0454] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the crimp angle of the fibers constituting the high dryness nonwoven fabric in Example D7 is 110°; the bulk density (0.2kPa) of the high dryness nonwoven fabric is 3.1%; and the bulk density (1.4kPa) of the high dryness nonwoven fabric is 6.4%; the average thickness H of the high dryness nonwoven fabric is 0.56mm.

[0455] The high dryness nonwoven fabric was measured to have a rewetting amount of 95 mg, a seepage rate of 1.17 s, and a softness (MD direction) of 49 mN.

[0456] Example D8

[0457] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the crimp angle of the fibers constituting the high dryness nonwoven fabric in Example D8 is 120°; the bulk density (0.2kPa) of the high dryness nonwoven fabric is 3.4%; and the bulk density (1.4kPa) of the high dryness nonwoven fabric is 6.9%; the average thickness H of the high dryness nonwoven fabric is 0.51mm.

[0458] The high dryness nonwoven fabric was measured to have a rewetting amount of 106 mg, a seepage rate of 1.24 s, and a softness (MD direction) of 48 mN.

[0459] Example D9

[0460] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the crimp angle of the fibers constituting the high dryness nonwoven fabric in Example D9 is 130°; the bulk density (0.2kPa) of the high dryness nonwoven fabric is 3.9%; and the bulk density (1.4kPa) of the high dryness nonwoven fabric is 7.3%; the average thickness H of the high dryness nonwoven fabric is 0.45mm.

[0461] The high dryness nonwoven fabric was measured to have a rewetting amount of 131 mg, a seepage rate of 1.3 s, and a softness (MD direction) of 50 mN.

[0462] Example D10

[0463] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the number of crimps of the fibers constituting the high dryness nonwoven fabric in Example D10 is 10 / 25mm; the bulk density (0.2kPa) of the high dryness nonwoven fabric is 3.8%; and the bulk density (1.4kPa) of the high dryness nonwoven fabric is 7.3%; the average thickness H of the high dryness nonwoven fabric is 0.46mm.

[0464] The high dryness nonwoven fabric was measured to have a rewetting amount of 133 mg, a seepage rate of 1.29 s, and a softness (MD direction) of 49 mN.

[0465] Example D11

[0466] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the number of crimps of the fibers constituting the high dryness nonwoven fabric in Example D11 is 12 / 25mm; the bulk density (0.2kPa) of the high dryness nonwoven fabric is 3.1%; and the bulk density (1.4kPa) of the high dryness nonwoven fabric is 6.3%; the average thickness H of the high dryness nonwoven fabric is 0.56mm.

[0467] The high dryness nonwoven fabric was measured to have a rewetting amount of 91 mg, a seepage rate of 1.17 s, and a softness (MD direction) of 49 mN.

[0468] Example D12

[0469] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the fiber crimp number of the high dryness nonwoven fabric constituting Example D12 is 15 crimps / 25mm; the bulk density (0.2kPa) of the high dryness nonwoven fabric is 2.9%; and the bulk density (1.4kPa) of the high dryness nonwoven fabric is 5.8%; the average thickness H of the high dryness nonwoven fabric is 0.60mm.

[0470] The high dryness nonwoven fabric was measured to have a rewetting amount of 82 mg, a seepage rate of 1.14 s, and a softness (MD direction) of 48 mN.

[0471] Example D13

[0472] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the number of crimps of the fibers constituting the high dryness nonwoven fabric in Example D13 is 24 / 25mm; the bulk density (0.2kPa) of the high dryness nonwoven fabric is 3.5%; and the bulk density (1.4kPa) of the high dryness nonwoven fabric is 6.9%; the average thickness H of the high dryness nonwoven fabric is 0.50mm.

[0473] The high dryness nonwoven fabric was measured to have a rewetting amount of 105 mg, a seepage rate of 1.25 s, and a softness (MD direction) of 49 mN.

[0474] Example D14

[0475] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the number of crimps of the fibers constituting the high dryness nonwoven fabric in Example D13 is 25 crimps / 25mm; the bulk density (0.2kPa) of the high dryness nonwoven fabric is 3.8%; and the bulk density (1.4kPa) of the high dryness nonwoven fabric is 7.2%; the average thickness H of the high dryness nonwoven fabric is 0.46mm.

[0476] The high dryness nonwoven fabric was measured to have a rewetting amount of 119 mg, a seepage rate of 1.28 s, and a softness (MD direction) of 50 mN.

[0477] This set of examples discusses the effects of different crimp angles and crimp numbers on the seepage rate and rewetting amount of nonwoven fabrics. This set of examples achieves changes in the bulk density of nonwoven fabrics by adjusting the crimp angle and crimp number of the core-sheath composite fibers. Generally, the crimp angle and crimp number of the core-sheath composite fibers can be changed by adjusting preparation process parameters such as crimp temperature and crimp pressure. Typically, too low a crimp temperature and too low a crimp pressure result in a larger crimp angle and fewer crimps; conversely, too high a crimp temperature and too high a crimp pressure result in a smaller crimp angle and more crimps. This set of examples achieves changes in the crimp angle and crimp number by adjusting the crimp temperature or crimp pressure. A comparison of Examples D1 and D5-D9 shows that when the curling angle is too small in Example D5 and too large in Example D9, the bulk density of the nonwoven fabric increases; the amount of rewetting increases and the infiltration rate slows down, resulting in a longer time value. This indicates that excessively large or small curling angles will increase the bulk density of the nonwoven fabric, affecting its rewetting and infiltration rates. Therefore, selecting a curling angle of 90°-120° is more beneficial for the bulk density, rewetting, and infiltration rate of the nonwoven fabric. Specifically, when the curling angle is selected between 90° and 120°, the bulk density (0.2 kPa) is relatively small, and the infiltration rate is faster; when the curling angle is selected between 90° and 120°, the bulk density (1.4 kPa) is 6.4%-6.9%, and the rewetting is relatively low. Further selection revealed that when the curling angle was set to 100°-110°, the bulk density (0.2 kPa) was lower, and the infiltration rate was further accelerated; when the curling angle was set to 100°-110°, the bulk density (1.4 kPa) was 6.4%-6.7%, and the re-infiltration rate was further reduced.

[0478] A comparison of Examples D1 and D10-D14 shows that when the number of crimps is too small in Example D10 and too large in Example D14, the bulk density of the nonwoven fabric increases; the amount of rewetting increases and the seepage rate slows down. This indicates that an excessively large or small number of crimps will increase the bulk density of the nonwoven fabric, affecting its rewetting and seepage rate. Therefore, selecting a crimp number of 12-24 (crimps / 25mm) is more conducive to obtaining the ideal bulk density of the nonwoven fabric. Specifically, when the number of crimps is selected as 12-24 (crimps / 25mm), the bulk density (0.2KPa) is relatively small, and the seepage rate is relatively fast; when the number of crimps is selected as 12-24 (crimps / 25mm), the bulk density (1.4KPa) is 5.8%-6.9%, and the rewetting is relatively low. Further selection revealed that when the number of coils was selected as 12-19 (coils / 25mm), the bulk density (0.2KPa) was lower, and the infiltration rate was further accelerated; when the number of coils was selected as 12-15 (coils / 25mm), the bulk density (1.4KPa) was 5.8%-6.3%, and the re-infiltration rate was further reduced.

[0479] III. The Influence of Dry Heat Shrinkage Rate on Infiltration and Reverse Osmosis Effects

[0480] Example D15

[0481] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the dry heat shrinkage rate of the fibers constituting the high dryness nonwoven fabric in Example D15 is 0.3%; the bulk density (0.2 kPa) of the high dryness nonwoven fabric is 3.7%; and the bulk density (1.4 kPa) of the high dryness nonwoven fabric is 7.1%; the average thickness H of the high dryness nonwoven fabric is 0.47 mm.

[0482] The high dryness nonwoven fabric was measured to have a rewetting amount of 111 mg, a seepage rate of 1.27 s, and a softness (MD direction) of 48 mN.

[0483] Example D16

[0484] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the dry heat shrinkage rate of the fibers constituting the high dryness nonwoven fabric in Example D16 is 2.2%; the bulk density (0.2 kPa) of the high dryness nonwoven fabric is 3.2%; and the bulk density (1.4 kPa) of the high dryness nonwoven fabric is 6.6%; the average thickness H of the high dryness nonwoven fabric is 0.54 mm.

[0485] The high dryness nonwoven fabric was measured to have a rewetting amount of 98 mg, a seepage rate of 1.18 s, and a softness (MD direction) of 49 mN.

[0486] Example D17

[0487] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the dry heat shrinkage rate of the fibers constituting the high dryness nonwoven fabric in Example D17 is 7%; the bulk density (0.2kPa) of the high dryness nonwoven fabric is 3.8%; and the bulk density (1.4kPa) of the high dryness nonwoven fabric is 7.2%; the average thickness H of the high dryness nonwoven fabric is 0.46mm.

[0488] The high dryness nonwoven fabric was measured to have a rewetting amount of 120 mg, a seepage rate of 1.29 s, and a softness (MD direction) of 52 mN.

[0489] Example D18

[0490] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the viscosity of the fiber core material constituting the high dryness nonwoven fabric in Example D18 is 0.6 dL / g, and the dry heat shrinkage rate is 0.3%; the bulk density (0.2 kPa) of the high dryness nonwoven fabric is 3.7%; and the bulk density (1.4 kPa) of the high dryness nonwoven fabric is 7.1%; the average thickness H of the high dryness nonwoven fabric is 0.47 mm.

[0491] The high dryness nonwoven fabric was measured to have a rewetting amount of 112 mg, a seepage rate of 1.27 s, and a softness (MD direction) of 44 mN.

[0492] This set of examples discusses the effect of the dry heat shrinkage rate of the core-sheath composite fiber on the bulk density of the nonwoven fabric.

[0493] This set of embodiments achieves the change of nonwoven fabric bulk density by adjusting the dry heat shrinkage rate of the core-sheath composite fiber. The dry heat shrinkage rate of the core-sheath composite fiber can typically be altered by adjusting raw material and preparation process parameters such as the viscosity of the polyester resin, heat setting temperature and time, and stretch ratio. Generally, the higher the viscosity of the polyester resin, the higher the dry heat shrinkage rate; too low a heat setting temperature or too short a time results in an excessively high dry heat shrinkage rate, while too high a heat setting temperature or too long a time results in an excessively low dry heat shrinkage rate. Too low a stretch ratio results in an excessively low dry heat shrinkage rate, while too high a stretch ratio results in an excessively high dry heat shrinkage rate.

[0494] A comparison of Examples D1 and D15-D18 shows that in Examples D15, D17, and D18, excessively high or low dry heat shrinkage rates increase the bulk density of the nonwoven fabric, leading to increased rewetting and seepage rates. This indicates that excessively high or low dry heat shrinkage rates increase the bulk density of the nonwoven fabric, affecting its rewetting and seepage rates. Therefore, a dry heat shrinkage rate greater than 0.3% and less than 7% results in a lower bulk density (0.2 kPa) and faster seepage rate, while a lower bulk density (1.4 kPa) results in a lower rewetting rate.

[0495] Comparing Example D1 with Example D1, it can be seen that excessive dry heat shrinkage can lead to a relatively stiff nonwoven fabric. Therefore, a dry heat shrinkage rate of 0.5%-2.2% can be further selected to balance the permeability and softness of the nonwoven fabric. Specifically, a dry heat shrinkage rate of 0.5%-2.2% results in better softness.

[0496] IV. The Influence of the Second Component of the Core Material on Flexibility

[0497] Example D19

[0498] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, in Example D19, a low-viscosity polyester resin is added to the fiber core material constituting the high-dryness nonwoven fabric; the viscosity of the low-viscosity polyester resin is 0.5 dL / g, and the low-viscosity polyester resin accounts for 2 wt% of the total polyester resin; the dry heat shrinkage rate of the fiber is 0.46%, and the number of crimps is 20 / 25 mm; the bulk density (0.2 kPa) of the high-dryness nonwoven fabric is 3.5%; and the bulk density (1.4 kPa) of the high-dryness nonwoven fabric is 7%; the average thickness H of the high-dryness nonwoven fabric is 0.5 mm.

[0499] The high dryness nonwoven fabric was measured to have a rewetting amount of 108 mg, a seepage rate of 1.25 s, and a softness (MD direction) of 42 mN.

[0500] Example D20

[0501] The difference from Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, in Example D20, a low-viscosity polyester resin is added to the fiber core material constituting the high-dryness nonwoven fabric; the viscosity of the low-viscosity polyester resin is 0.7 dL / g, and the amount of low-viscosity polyester resin in the total polyester resin is 5 wt%; the dry heat shrinkage rate is 0.49%, and the number of crimps is 20 / 25 mm; the bulk density (0.2 kPa) of the high-dryness nonwoven fabric is 3.4%; and the bulk density (1.4 kPa) of the high-dryness nonwoven fabric is 6.9%; the average thickness H of the high-dryness nonwoven fabric is 0.51 mm.

[0502] The high dryness nonwoven fabric was measured to have a rewetting amount of 105 mg, a seepage rate of 1.24 s, and a softness (MD direction) of 38 mN.

[0503] This set of examples discusses the effect of introducing low-viscosity components into polyester resin on the softness of nonwoven fabrics. These examples achieve a change in the softness of nonwoven fabrics by introducing low-viscosity components into polyester resin. Generally, the introduction of low-viscosity components into polyester resin alters properties such as dry heat shrinkage. A comparison of Examples D1 and Examples D19-D20 shows that the softness of Examples D19-D20 improves after the introduction of the low-viscosity component. This is because the introduction of low-viscosity components into polyester resin can regulate the slippage ability between resin molecular chains, resulting in greater deformation capacity to dissipate external forces when subjected to them, thus making the fabric feel softer. Therefore, introducing low-viscosity components into polyester resin can effectively improve the softness of nonwoven fabrics. Further, a low-viscosity polyester component with a viscosity of 0.5 dL / g-0.7 dL / g can be introduced into the polyester resin to improve the softness of the nonwoven fabric. The amount of this low-viscosity polyester component can be selected from 2 wt% to 5 wt%. Within this range, the material's low backflow and seepage rate remain at ideal levels.

[0504] V. The Influence of Specific Surface Area on the Re-weave Properties of Nonwoven Fabrics

[0505] Example D21

[0506] The difference between Example D1 and Example D21 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the fiber d / R ratio of the high-dryness nonwoven fabric in Example D21 is 10%, and it has an eccentric structure; the bulk density (0.2 kPa) of the high-dryness nonwoven fabric is 3.3%; and the bulk density (1.4 kPa) of the high-dryness nonwoven fabric is 6.8%; the average thickness H of the high-dryness nonwoven fabric is 0.53 mm, and the specific surface area is 0.06 m². 2 / g.

[0507] The high dryness nonwoven fabric was measured to have a rewetting amount of 116 mg, a seepage rate of 1.22 s, and a softness (MD direction) of 49 mN.

[0508] Example D22

[0509] The difference between Example D22 and Example D1 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the fiber d / R ratio of the high-dryness nonwoven fabric in Example D22 is 15%, and it has an off-center structure; the bulk density (0.2 kPa) of the high-dryness nonwoven fabric is 3.2%; and the bulk density (1.4 kPa) of the high-dryness nonwoven fabric is 6.8%; the average thickness H of the high-dryness nonwoven fabric is 0.54 mm, and the specific surface area is 0.05 m². 2 / g.

[0510] The high dryness nonwoven fabric was measured to have a rewetting amount of 122 mg, a seepage rate of 1.18 s, and a softness (MD direction) of 49 mN.

[0511] This set of embodiments achieves changes in the rewetting properties of nonwoven fabrics by altering their specific surface area. The inventors discovered that the specific surface area can be changed by adjusting the eccentric structure of the fibers. Generally, the smaller the d / R value of the eccentric structure, the larger the specific surface area of ​​the resulting nonwoven fabric.

[0512] A comparison of Examples D1 and D21-D22 shows that when the specific surface area is too low, the amount of rewetting of the nonwoven fabric increases. Therefore, when the d / R value is ≤10%, and more preferably a co-core structure (d / R value ≤1%), the larger the specific surface area, the better the anti-rewetting effect of the nonwoven fabric.

[0513] VI. The Influence of Fineness on the Wetness and Rewetting Properties of Nonwoven Fabrics

[0514] Example D23

[0515] The difference between Example D2 and Example D3 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the fibers constituting the high-dryness nonwoven fabric in Example D23 differ in that the fineness of the core-sheath composite fiber is 0.8 dtex; the bulk density (0.2 kPa) of the high-dryness nonwoven fabric is 3.7%; and the bulk density (1.4 kPa) of the high-dryness nonwoven fabric is 7.2%; the average thickness H of the high-dryness nonwoven fabric is 0.66 mm, and the specific surface area is 0.13 m². 2 / g.

[0516] The high dryness nonwoven fabric was measured to have a rewetting amount of 110 mg, a seepage rate of 1.28 s, and a softness (MD direction) of 21 mN.

[0517] Example D24

[0518] The difference between Example D24 and Example D3 lies in the following components and structural parameters of the nonwoven fabric: Specifically, the fibers constituting the high-dryness nonwoven fabric in Example D24 differ in that the fineness of the core-sheath composite fiber obtained is 11 dtex; the bulk density (0.2 kPa) of the high-dryness nonwoven fabric is 3.2%; and the bulk density (1.4 kPa) of the high-dryness nonwoven fabric is 6.6%; the average thickness H of the high-dryness nonwoven fabric is 0.54 mm, and the specific surface area is 0.04 m². 2 / g.

[0519] The high dryness nonwoven fabric was measured to have a rewetting amount of 103 mg, a seepage rate of 1.21 s, and a softness (MD direction) of 69 mN.

[0520] This set of examples discusses the effect of fiber fineness on the bulk density of nonwoven fabrics. These examples demonstrate how changing the fiber fineness alters the bulk density of nonwoven fabrics.

[0521] A comparison of Examples D2 and D23 shows that when the fiber density is too low, the bulk density of the nonwoven fabric increases, the amount of rewetting increases, and the seepage rate slows down, but the softness improves. A comparison of Examples D3 and D24 shows that when the fiber density is too high, the bulk density of the nonwoven fabric decreases, the amount of rewetting decreases, and the seepage rate speeds up, but the softness deteriorates. Therefore, selecting a fiber density of 1 dtex to 10 dtex is more beneficial to the permeability and softness of the nonwoven fabric.

[0522] VII. The Influence of Hot Air Process on the Bulk Density of Nonwoven Fabrics

[0523] Example D25

[0524] Example D25 is prepared by process C25. The difference between Example D1 and Example D25 lies in the following components and structural parameters of the nonwoven fabric: specifically, the bulk density (0.2 kPa) of the high-dryness nonwoven fabric is 3.7%; the bulk density (1.4 kPa) of the high-dryness nonwoven fabric is 7.1%; the average thickness H of the high-dryness nonwoven fabric is 0.47 mm, and the specific surface area is 0.06 m². 2 / g.

[0525] The high dryness nonwoven fabric was measured to have a rewetting amount of 119 mg, a seepage rate of 1.27 s, and a softness (MD direction) of 47 mN.

[0526] Example D26

[0527] Example D26 is prepared by process C26. The difference between Example D1 and Example D26 lies in the following components and structural parameters of the nonwoven fabric: specifically, the bulk density (0.2 kPa) of the high-dryness nonwoven fabric is 3.8%; the bulk density (1.4 kPa) of the high-dryness nonwoven fabric is 7.2%; the average thickness H of the high-dryness nonwoven fabric is 0.46 mm, and the specific surface area is 0.06 m². 2 / g.

[0528] The high dryness nonwoven fabric was measured to have a rewetting amount of 128 mg, a seepage rate of 1.28 s, and a softness (MD direction) of 49 mN.

[0529] Example D27

[0530] Example D27 is prepared by process C27. The difference between Example D1 and Example D27 lies in the following components and structural parameters of the nonwoven fabric: specifically, the bulk density (0.2 kPa) of the high-dryness nonwoven fabric is 3.9%; the bulk density (1.4 kPa) of the high-dryness nonwoven fabric is 7.3%; the average thickness H of the high-dryness nonwoven fabric is 0.45 mm, and the specific surface area is 0.05 m². 2 / g.

[0531] The high dryness nonwoven fabric was measured to have a rewetting amount of 137 mg, a seepage rate of 1.3 s, and a softness (MD direction) of 48 mN.

[0532] This set of examples discusses how the hot air process primarily affects the bulk density of nonwoven fabrics, thereby influencing the amount of rewetting and the rate of seepage. These examples demonstrate how altering the short fiber processing temperature, the frequency of the short fiber processing blower, and the processing time in the hot air process can change the bulk density of the nonwoven fabric. These changes in hot air process parameters will also slightly alter the specific surface area.

[0533] A comparison of Examples D1 and D25 shows that when the temperature is too high, the bulk density of the nonwoven fabric increases, the specific surface area of ​​the nonwoven fabric decreases, the amount of rewetting increases, and the seepage rate slows down. A comparison of Examples D1 and D26 shows that when the pressure is too high, the bulk density of the nonwoven fabric increases, the specific surface area of ​​the nonwoven fabric decreases, the amount of rewetting increases, and the seepage rate slows down. A comparison of Examples D1 and D27 shows that when the time is too long, the bulk density of the nonwoven fabric increases, the specific surface area of ​​the nonwoven fabric decreases, the amount of rewetting increases, and the seepage rate slows down. Therefore, excessively high temperature, excessive pressure, or excessively long time leads to excessive surface adhesion between fibers, which in turn increases the bulk density of the nonwoven fabric and reduces the specific surface area of ​​the fibers, negatively impacting the rewetting performance of the nonwoven fabric.

[0534] Example D28

[0535] Example D28 is prepared by process C28. The difference between Example D1 and Example D28 lies in the following components and structural parameters of the nonwoven fabric: specifically, the bulk density (0.2 kPa) of the high-dryness nonwoven fabric is 3.4%; the bulk density (1.4 kPa) of the high-dryness nonwoven fabric is 6.9%; the average thickness H of the high-dryness nonwoven fabric is 0.41 mm, and the specific surface area is 0.08 m². 2 / g.

[0536] The high dryness nonwoven fabric was measured to have a rewetting amount of 112 mg, a seepage rate of 1.17 s, and a softness (MD direction) of 49 mN.

[0537] A comparison of Example D1 and Example D28 shows that, while maintaining the same bulk density and specific surface area, the basis weight of the nonwoven fabric decreases, the amount of rewetting increases, and the seepage rate becomes faster.

[0538] Example E: Absorbent Product

[0539] An absorbent product includes a surface nonwoven fabric, an absorbent core assembly, and a waterproof membrane, which are stacked sequentially on the side facing human skin.

[0540] The aforementioned “surface nonwoven fabric” refers to the high-dryness nonwoven fabric spun in the aforementioned embodiments D1-D28.

[0541] An absorbent article, the absorbent article further comprising a wearable component consisting of an adhesive backing and a release paper, or the wearable component consisting of elastic components forming a waist opening and a leg opening.

[0542] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A nonwoven fabric, characterized in that, The fiber material constituting the nonwoven fabric is a core-sheath composite fiber, which includes a sheath and a core. At least a portion of the sheath melts, causing the composite fiber sheaths to be thermally bonded to each other to form bonding points. The core material of the core-sheath composite fiber accounts for 20%-80% of the total mass. The substrate of the sheath includes polyethylene resin, and the substrate of the core material includes polyester resin, and includes at least one of polybutylene terephthalate resin or polypropylene terephthalate resin. The bulk density (0.2 kPa) of the nonwoven fabric is ≤3.9%.

2. The nonwoven fabric according to claim 1, characterized in that, The bulk density of the woven fabric (0.2 kPa) is ≤3.5%; and / or the bulk density of the nonwoven fabric (1.4 kPa) is ≤7.3%; Preferably, the bulk density (1.4 kPa) of the nonwoven fabric is ≤6.9%.

3. The nonwoven fabric according to claim 1, characterized in that, The crimp angle of the core-sheath composite fiber is 65°-130°; Preferably, the crimp angle of the core-sheath composite fiber is 90°-120°.

4. The nonwoven fabric according to claim 1, characterized in that, The core-sheath composite fiber has a crimp count of 10-25mm to 25-25mm. Preferably, the number of crimps in the core-sheath composite fiber is 12-24 / 25mm.

5. The nonwoven fabric according to claim 1, characterized in that, The average thickness of the nonwoven fabric is >0.40 mm; Preferably, the average thickness of the nonwoven fabric is ≥0.45mm, more preferably ≥0.50mm; The weight of the nonwoven fabric is 16 g / m² to 30 g / m².

6. The nonwoven fabric according to claim 1, characterized in that, The dry heat shrinkage rate of the core-sheath composite fiber is 0.3%-7%; Preferably, the dry heat shrinkage rate of the core-sheath composite fiber is 0.5-5%; more preferably, the dry heat shrinkage rate of the core-sheath composite fiber is 0.5-2.2%.

7. The nonwoven fabric according to claim 1, characterized in that, The viscosity of the polyester resin is controlled between 0.8 dL / g and 1.3 dL / g.

8. The nonwoven fabric according to claim 5, characterized in that, The core material of the sheath-core composite fiber includes a low-viscosity polyester resin, which is a similar polyester resin with a viscosity of 0.5 dL / g-0.7 dL / g. The amount of low-viscosity polyester resin in the total polyester resin should be controlled between 2wt% and 5wt%.

9. The nonwoven fabric according to claim 1, characterized in that, The specific surface area of ​​the nonwoven fabric is ≥0.04m². 2 / g; Preferably, the specific surface area of ​​the nonwoven fabric is ≥0.05m² / g; more preferably, the specific surface area is ≥0.07m² / g; even more preferably, the specific surface area is ≥0.08m² / g; and most preferably, the specific surface area is ≥0.11m² / g.

10. The nonwoven fabric according to claim 1, characterized in that, The core-sheath composite fiber has a restricted eccentric structure, specifically d / R ≤ 33%; preferably d / R ≤ 15%; more preferably d / R ≤ 10%; and most preferably d / R ≤ 1%.

11. The nonwoven fabric according to claim 1, characterized in that, The core-sheath composite fiber has a fineness of 0.8 dtex-11 dtex; preferably 1 dtex-10 dtex.

12. The nonwoven fabric according to claim 1, characterized in that, The melt index (170℃·2.16Kg) of the polyethylene resin is 7.8-18g / 10min.

13. The nonwoven fabric according to any one of claims 1-10, characterized in that, The nonwoven fabric is used in absorbent articles and is disposed on the absorbent core and on the side facing human skin.

14. A method for preparing a nonwoven fabric, characterized in that, This includes fiber spinning processes and hot air processes; The spinning process of the fiber includes: using a polyester resin containing at least one or two of polybutylene terephthalate resin or polypropylene terephthalate resin as the core material; using a substrate containing polyethylene resin as the sheath material; spinning the core material and the sheath material to obtain core-sheath composite fiber filament; and performing post-stretching, crimping, and heat setting on the core-sheath composite fiber filament. The hot air process includes: the short-cut fibers of the core-sheath composite fiber are combed and hot-air bonded to obtain the nonwoven fabric.

15. The method for preparing nonwoven fabric according to claim 12, characterized in that, The process of spinning the core material and the sheath material to obtain core-sheath composite fiber nascent yarn includes: Select a spinneret with a concentric or eccentric structure for spinning targets, and control the spinning temperature at 250℃-275℃ and the spinning speed at 1000m / min-1500m / min.

16. The method for preparing nonwoven fabric according to claim 12, characterized in that, Post-stretching of the core-sheath composite fiber nascent filament includes: When post-stretching the nascent filaments of the core-sheath composite fiber, the stretching ratio is controlled to be 2-4 times; preferably 2.5-3.5 times.

17. The method for preparing nonwoven fabric according to claim 12, characterized in that, The process of crimping the nascent core-sheath composite fiber includes: When the core-sheath composite fiber nascent filaments are crimped, the crimping temperature is controlled at 58℃-90℃ and the crimping pressure is 0.07-0.44MPa.

18. The method for preparing nonwoven fabric according to claim 12, characterized in that, Heat setting of the nascent core-sheath composite fiber includes: When heat-setting the nascent filaments of the core-sheath composite fiber, the heat-setting temperature is controlled at 110℃-125℃ and the drying time is 5min-15min.

19. The method for preparing nonwoven fabric according to claim 12, characterized in that, include: The core-sheath composite fiber is selected as the fiber raw material for nonwoven fabric, and the initial processing state of the fiber is short fiber, including: The selected short fiber length is 38mm-51mm.

20. The method for preparing nonwoven fabric according to claim 12, characterized in that, include: The obtained core-sheath composite fiber is then combed, including: The cut short fibers are placed on a carding machine for carding and laid into a web. The carding machine cylinder speed is 50-65 Hz, the doffer speed is 30-47 Hz, and the target weight of the fiber web is controlled to be 11-21 g / m².

21. The method for preparing nonwoven fabric according to claim 12, characterized in that, include: The prepared core-sheath composite fibers are hot-air bonded, including: The combed short fibers are processed at a temperature of 130-150℃ and a blower frequency of 35-55HZ for 3-20 seconds to bond them into a nonwoven fabric. Preferably, the processing temperature is 130-145℃; Preferably, the blower frequency is 35-45 Hz; Preferably, the processing time is 3-10 seconds.

22. An absorbent article, characterized in that, The nonwoven fabric layer on the side facing the human skin relative to the absorbent core in the absorbent article is the nonwoven fabric described in claims 1-13; or, the nonwoven fabric layer on the side facing the human skin relative to the absorbent core in the absorbent article is the nonwoven fabric prepared by the method described in claims 14-21. Optionally, the surface nonwoven fabric in the absorbent article is the nonwoven fabric as described in claims 1-13; Optionally, the surface nonwoven fabric in the absorbent article is the nonwoven fabric prepared by the method described in claims 14-19.

23. The absorbent article according to claim 22, characterized in that, The absorbent products include any one of the following: feminine hygiene products, panty liners, diapers, pull-up diapers, nursing pads, or diaper pads.

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