HK1170781B

HK1170781B - Nonwoven fabric, manufacturing method thereof and filters formed by it

Info

Publication number: HK1170781B
Application number: HK12111390.9A
Authority: HK
Inventors: 吴莹旭; G．克雷格
Original assignee: 崇鸣投资有限公司
Priority date: 2010-10-14
Filing date: 2011-02-28
Publication date: 2015-11-20

Description

Nonwoven fabric, method for producing same, and filter formed from same

Technical Field

The present invention relates to a nonwoven fabric having excellent hardness, stiffness, moldability and compressive strength, a method for manufacturing the same, and a filter formed from the nonwoven fabric as a material for manufacturing a filter medium.

Background

Non-woven fabrics, also called non-woven fabrics and non-woven fabrics, are fabrics formed without spinning woven fabrics, and are formed by forming a fiber web structure by orienting or randomly arranging textile short fibers or long fibers (filaments) and then reinforcing the fiber web structure by mechanical, thermal bonding or chemical methods. In short, the yarn is not interwoven and knitted together by yarns one by one, but the fibers are directly bonded together by a physical method. The non-woven fabric breaks through the traditional spinning principle and has the characteristics of short process flow, high production speed, high yield, low cost, wide application, multiple raw material sources and the like.

Nonwoven fabrics have good filterability, air permeability and adsorptivity and are very suitable for use as filter elements in filters, for example in bag filters or cartridge filters. However, conventional nonwoven fabrics are generally soft and may be installed in the filter by means of a support frame. Fig. 1 shows a prior art cylindrical filter comprising two end caps 12, 14 each having a circular ring shape and a mesh support frame 16 between the two end caps, and a filter element made of a non-woven fabric may be installed on the inside, outside or both sides of the mesh support frame 16. This construction increases on the one hand the material costs and the complexity of the assembly of the filter and on the other hand also reduces the filtering performance of the nonwoven filter element to a greater or lesser extent, since the net-like support frame may block the nonwoven filter element from contact with the material flowing through or may accumulate dust or dirt. Several techniques have been proposed in the prior art to increase the stiffness or bending stiffness of nonwoven fabrics.

Chinese patent application No. 200880017579.5 (publication No. CN 101678255A), published 24/3/2010, discloses a long fiber nonwoven fabric formed of synthetic fibers and formed by partial thermocompression bonding of thermoplastic continuous filaments, wherein the circular arc bending stiffness per unit area weight is preferably 0.050 to 1.000 ((CN/2 cm)/(g/m), and a cylindrical bag filter using the same²) And the air permeability per unit area weight is preferably 0.010 to 0.500 ((cc/cm)²/sec）/（g/m²)). The long fiber nonwoven fabric is substantially a spunbond (spunbond) nonwoven fabric, and is produced by melt-extruding a thermoplastic polymer from a spinneret, drawing and stretching the thermoplastic polymer by a suction device to form thermoplastic continuous filaments, electrically splitting the thermoplastic continuous filaments to deposit the filaments on a moving collecting surface to form a web, pressure-bonding the web by a smooth roll, and then partially pressure-bonding the web by a hot embossing roll. The long fiber nonwoven fabric obtained in this application has good bending stiffness, and is suitable for use in the production of bag filters, and is excellent in shape retention when used with backwash air. However, this patent application teaches that conventional nonwoven fabrics made of short fibers such as felt are not suitable because they lack the rigidity of the sheet. The long fiber nonwoven fabric in this application has a certain rigidity, but the rigidity is not high enough, and the long fiber nonwoven fabric can maintain its form only in a relatively short size (for example, about 30 cm), but still requires a support structure, and not to say, a filter bag formed of the nonwoven fabric cannot be self-supported in a filter having a long size (for example, 1 meter or more).

Chinese patent application No. 200810138481.7 (publication No. CN 101332385A), published on 31.12.2008, discloses a material for an air filter of a centralized ventilation system, which mainly comprises an upper non-woven fabric layer and a lower non-woven fabric layer as base materials, and one or more composite layers compounded between the two non-woven fabrics layers, and is characterized in that the composite layers are composed of granular activated carbon layers wrapped between two fibrous adhesives, and the granular activated carbon layers are paved by independent activated carbon granules; the filter material has high efficiency, low resistance, original adsorption performance of the active carbon, hardness and stiffness of common ventilation filter materials, and monotonous form of a chemical air filter, so that the filter material has the form of the common ventilation air filter. Although the patent application does not limit the types of fibers of the upper and lower non-woven fabrics, the patent actually comprises the upper and lower non-woven fabrics respectively adhered on the middle activated carbon layer, and the hardness and the stiffness of the obtained filter material can be adjusted by adjusting the amount of the activated carbon layer and the amount of glue so as to adapt to the requirements of the pleating process of the filter material. The filtering material of the patent application has a complex structure, the used glue for bonding is not environment-friendly, and the filtering performance of the filtering material is reduced due to the fact that the glue can block partial pores of the activated carbon layer or the non-woven fabric layer.

In addition, the conventional needle-punched non-woven fabric (felt) is generally soft and cannot be pleated. Therefore, the existing needle-punched non-woven fabric can not be made into a filter with a fold shape so as to increase the filtering area. Further, the conventional needle-punched nonwoven fabric has no moldability, that is, cannot be molded into various shapes or cannot maintain the shape after molding.

Therefore, heretofore, there has been no disclosure in the prior art of a needle-punched non-woven fabric (felt) having high rigidity so as to be self-supporting with form retention and moldability and capable of being pleated; no pleated filter was found made from needle punched non-woven fabric (felt) which was self-supporting to form the filter media of the filter without the use of a support frame.

Disclosure of Invention

An object of the present invention is to provide a nonwoven fabric which has excellent hardness or rigidity or stiffness, excellent moldability, and very high compressive strength.

Another object of the present invention is to provide a method for producing the nonwoven fabric and a filter formed of the nonwoven fabric.

In order to achieve the above object, the present invention provides a nonwoven fabric made of at least two types of short fibers of the same kind or different kinds having a low melting point and a high melting point, respectively, the nonwoven fabric having a hardness sufficient to enable the nonwoven fabric to be self-supporting with form retention, and the nonwoven fabric having moldability.

The non-woven fabric may be a single-layer fiber layer formed by uniformly mixing the low-melting-point short fibers and the high-melting-point short fibers, or the non-woven fabric includes low-melting-point short fiber layers and high-melting-point short fiber layers which are alternately stacked.

The low-melting-point short fiber is formed by being heated and melted into a molten state to entangle the high-melting-point fiber, and then being rapidly cooled and solidified, thereby increasing the connection between the low-melting-point fiber and the high-melting-point fiber.

In a preferred embodiment of the present invention, the nonwoven fabric comprises two layers of high-melting-point short fibers and one layer of low-melting-point short fibers sandwiched between the two layers of high-melting-point short fibers.

The high-melting-point short fiber has a melting point in the range of 180 ℃ to 230 ℃ and the low-melting-point short fiber has a melting point in the range of 115 ℃ to 130 ℃.

The low-melting-point staple fiber and the high-melting-point staple fiber can be selected from polyester, terylene, polypropylene fiber, nylon, acrylic, chinlon, viscose fiber, acrylic fiber, polyethylene and polyvinyl chloride.

The Shore A hardness of the non-woven fabric can reach 50-80 degrees.

The nonwoven may be pleated.

The content of the low-melting-point short fibers determines the hardness of the nonwoven fabric. The low-melting-point short fiber accounts for 20-50 wt% of the whole non-woven fabric material, and the high-melting-point short fiber accounts for 50-80 wt% of the whole non-woven fabric material. Preferably, the low-melting-point fibers account for 30% -40% of the whole non-woven fabric material, and the high-melting-point short fibers account for 60% -70% of the whole non-woven fabric material.

Preferably, the nonwoven fabric is obtained in the following manner: after the low-melting point and high-melting point fibers are formed into a raw fabric, the raw fabric is heat-treated at a temperature lower than the melting point of the high-melting point fibers but higher than the melting point of the low-melting point fibers to melt the low-melting point fiber layer into a molten state and entangle the high-melting point fibers, and then rapidly cooled to form the fiber composite.

The gram weight of the non-woven fabric is 150-2000g/m²Within the range.

The nonwoven fabric may be a nonwoven fabric obtained by needle punching or hydroentanglement setting.

The nonwoven fabric of the present invention is suitable for use as a filter medium for gas-solid and liquid-solid separation filters. Therefore, the present invention also provides a filter using the nonwoven fabric of the present invention as a material for a filter medium of the filter, which is self-supporting without using any support structure.

In one embodiment of the invention, the filter is a cartridge filter, the non-woven fabric forms a cylindrical filter cartridge, and the filter cartridge is self-supporting without any supporting structure. Preferably, the filter cartridge is formed in a pleated shape. The filter may further comprise an end cap made of the non-woven fabric of the present invention, the surface profile of which is molded to correspond to the cross-sectional shape of the filter cartridge in the pleated shape.

In another embodiment of the invention, the filter is a bag filter, the nonwoven fabric is molded into the filter bag of the bag filter, or the nonwoven fabric is pleated and then rolled into the filter bag of the bag filter and the opposite edges are sealed in a manner known in the art, for example, by using a sealant or by sewing. The filter bag is self-supporting.

In still another embodiment of the present invention, the filter is a CGR insert plate type filter including a first filter element, a second filter element opposite to the first filter element, and an insert support plate having a central through hole interposed therebetween, wherein the first and second filter elements are molded from the non-woven fabric.

The first and second filter elements each include a filter element body, a cylindrical core formed at the center of the filter element body, and a flange formed at the periphery of the filter element body, the cylindrical core and the flange protrude outward on the same side of the filter element body, and the filter element body, the cylindrical core, and the flange are integrally molded from the nonwoven fabric; the cylindrical core of the first filter element is shaped and dimensioned to extend just past the central through-hole of the insert support plate, and the cylindrical core of the second filter element is shaped and dimensioned to extend just past the cylindrical core of the first filter element and to intermesh together; the flanges of the first and second filter elements are shaped and dimensioned to fit within a groove formed along the periphery of the embedded support plate.

In still another embodiment of the present invention, the filter is a rotary disc filter formed by connecting a plurality of fan-shaped filter elements to each other, the fan-shaped filter elements each including a first filter wall made of the nonwoven fabric and a second filter wall made of the nonwoven fabric and opposed to the first filter wall, the first and second filter walls forming a filtrate chamber therebetween to accommodate the filtrate flowing through the first and second filter walls. Preferably, the sector filter element further comprises a support plate accommodated in the filtrate chamber, the support plate is formed by molding the non-woven fabric, and the support plate is shaped to form a plurality of grooves along a radial direction of the support plate to guide the filtrate to flow through the grooves toward the filtrate outlet.

According to the invention, the first and second filtering walls can be shaped so that they engage each other to form a closed pocket.

The invention also relates to a rotary disk filter comprising a plurality of fan-shaped support elements connected to one another and filter pockets for enclosing the fan-shaped support elements, wherein the fan-shaped support elements are formed by embossing the nonwoven fabric of the invention. Preferably, the support plate is profiled to form a plurality of grooves radially of the support plate to direct filtrate through the grooves towards the filtrate outlet.

The invention also provides a non-woven fabric manufacturing method, which comprises the following steps:

1) putting the cotton-shaped high-melting-point short fibers and the low-melting-point short fibers into a cotton mixing box according to a required proportion to uniformly mix the high-melting-point short fibers and the low-melting-point short fibers to prepare single-layer fibers, or alternately putting the cotton-shaped high-melting-point short fibers and the low-melting-point short fibers into the cotton mixing box according to the required proportion to uniformly mix the high-melting-point short fibers and the low-melting-point short fibers respectively to prepare multi-layer fibers;

2) conveying the mixed fibers to a carding machine for carding;

3) sending the carded fibers to a lapping machine again to be lapped into a net-shaped plane;

4) sending the reticular planar fibers into a forming machine for shaping treatment to prepare grey cloth;

5) heat-treating the raw fabric at a temperature higher than the melting point of the low-melting-point short fibers but lower than the melting point of the high-melting-point short fibers to melt the low-melting-point short fibers but to maintain the high-melting-point fibers in an unmelted state;

6) and cooling the grey fabric after the heat treatment to solidify the molten low-melting-point short fiber to obtain the non-woven fabric.

Wherein the low-melting-point short fibers are melted during the heat treatment to become a molten state entangling the high-melting-point fibers, and the high-melting-point short fibers are not melted, whereby the structure of the raw fabric becomes that the melted low-melting-point short fibers are sandwiched between the non-melted high-melting-point short fibers.

The melting point of the high-melting-point short fiber is 180-230 ℃, the melting point of the low-melting-point short fiber is 115-130 ℃, the temperature of the heat treatment is 140-150 ℃, and the temperature of the cooling is 10-18 ℃.

In the heat treatment process, hot air is blown to the upper surface and the lower surface of the grey cloth in the vertical direction, so that the hot air directly penetrates through the grey cloth, and the internal low-melting-point fiber layer obtains a better heating effect.

In the cooling process, a cooling roller, for example, of 200kg weight, is pressed down onto the blank in the form of its own weight or by means of oil pressure, and the blank is rapidly cooled.

The nonwoven fabric may be pleated to form a pleated nonwoven fabric.

In step 4) of the above method, the setting treatment comprises forming the raw fabric using a process step selected from the group consisting of needle punching, hydro-entangling, heat sealing, thermal bonding, pulp air-laying, wet or stitch-bonding.

Drawings

FIG. 1 is a schematic view of a prior art cartridge filter.

Fig. 2 is a perspective sectional view of a nonwoven fabric having a three-layer structure according to one embodiment of the present invention.

Fig. 3 is a perspective cross-sectional view of the nonwoven fabric forming corrugated structure shown in fig. 2.

Fig. 4 is a schematic perspective view of a cartridge filter formed of the nonwoven fabric of the present invention.

Fig. 5 is a perspective view schematically showing another cartridge filter formed of the nonwoven fabric of the present invention.

Fig. 6 is a perspective view of a bag filter formed of the nonwoven fabric of the present invention.

Fig. 7 is a schematic perspective view of another bag filter formed of the nonwoven fabric of the present invention.

Fig. 8 is a front view of an embedded support plate of a CGR plate filter integrally formed of the non-woven fabric of the present invention.

Fig. 9 is a front view of a filter element of a CGR panel filter integrally formed of the non-woven fabric of the present invention.

Fig. 10 is a schematic view of the embedded support plate of fig. 9 and the filter element of fig. 9 in a state prior to being ready for installation.

Fig. 11 is a side view of the embedded support plate and filter element of fig. 10 installed as a CGR panel filter.

Fig. 12 is a front view of a support plate for a rotary disc filter integrally formed of the nonwoven fabric of the present invention.

Fig. 13 is a side view of filter walls formed of the nonwoven fabric of the present invention joined to each other to form a closed chamber in which the support plate shown in fig. 12 is accommodated.

Detailed Description

The present invention relates generally to nonwoven fabrics made from staple fibers by processes such as needle punching, which have excellent stiffness or rigidity; it also exhibits very good moldability, and is able to retain any shape or configuration after being molded into it. Nonwoven fabrics made by Needle punching are known as Needle punched felts (Needle felts), whereas felts or felts (felts) are generally sheet-like structures made by tightly bonding, for example, wool or wool pile fibers.

The constituent materials of nonwoven fabrics can be divided into long fibers and short fibers, in general, long fibers like cocoon filaments of silkworm cocoons and short fibers like wool (commonly known asWool) or cotton. The long fibers are continuous single fibers, and the grammage of the nonwoven fabric made of the long fibers is generally about 200-300g/m²(grams per square meter). The grammage is the gram of material weight per square meter, and is an important technical index in the textile field, and is generally used for measuring the thickness and the density of fabrics.

The short fibers are also called staple fibers (usually 35 to 74mm), which are fibers obtained by cutting or stretch-breaking chemical long fiber bundles into various lengths corresponding to natural fibers, and may be formed of natural fibers such as whiskers and asbestos. The length of the short fiber used in the invention is 35-150 mm, and the thickness (fineness) of the short fiber is generally 1.5-8D (denier). It can be divided into cotton type, wool type, carpet type and middle and long type short fibers according to the specification of natural fibers. They can be spun either pure or blended with natural or other fibers in different proportions to make slivers, fabrics and felts. The gram weight of the needle-punched non-woven fabric prepared by the method of the invention is about 150-2000g/m²。

Fig. 2 is a schematic structural view of a short fiber nonwoven fabric having excellent stiffness according to one embodiment of the present invention.

It is to be noted that fig. 1 and 4 are drawn to scale photographs of filters according to the prior art and the present invention; while the cross-sectional views of the nonwoven fabric of the invention of fig. 2 and 3 are schematic and not drawn to scale. In the three-layer structure nonwoven fabric shown in fig. 2, although it can be clearly seen that the cross section has three layers, the interface between the three layers may not be clear, that is, the high melting point and low melting point fibers are interlaced and interpenetrated with each other at the interface of the two layers because the needle punching process and the low melting point fibers are melted at the time of the heat treatment. Also, in fig. 2 and 3, the thickness of the nonwoven fabric is large relative to the surface of the nonwoven fabric for clarity, but the thickness of an actual nonwoven fabric product may be only 1-5 mm, while the surface of the nonwoven fabric may be as long as 1-2 m.

According to the present invention, the nonwoven fabric may be composed of a single layer of fibers in which the fiber layer is formed by uniformly mixing low-melting point staple fibers and high-melting point staple fibers. Specifically, high-melting-point short fibers and low-melting-point short fibers in a certain proportion are put into a cotton mixing box to be uniformly mixed, and the mixed fibers are conveyed to a carding machine to be combed flat; then the fiber raw material enters an auxiliary net machine to form a net plane; then, the fiber raw material is pre-needled, main barbed and normal needled by a forming machine to form a needled gray fabric and the needled gray fabric is wound up. The manufacturing of the non-woven grey cloth is completed through the steps. Then, the process proceeds to a step of solidifying the grey fabric, namely, subjecting the grey fabric to heat treatment at a temperature (for example, 140 ℃ C.) higher than the melting point of the low-melting-point short fibers but lower than the melting point of the high-melting-point short fibers so as to melt the low-melting-point short fibers, but keep the high-melting-point fibers in an unmelted state; finally, a rapid cooling treatment is immediately carried out, for example, the raw fabric is rapidly cooled to 10 to 18 ℃ within 5 to 15 seconds, and a cooling roller with a weight of about 200kg is applied to press down the raw fabric in a self-weight manner or by oil pressure, so that the raw fabric is solidified into a needle-punched non-woven fabric.

The nonwoven fabric of the present invention may also comprise two or more fiber layers formed of short fibers having different melting points, which are alternately arranged, for example, three layers of fibers in which a layer of short fibers having a low melting point is sandwiched between two layers of short fibers having a high melting point. Of course, the nonwoven fabric of the present invention may also comprise more layers of fibers, wherein each layer of fibers is formed from staple fibers having different melting points, and the number of fibers in each layer of fibers depends on the thickness of the layer of fibers in the final product, depending on the specific application requirements.

The steps for producing the nonwoven fabric of the multilayer structure are substantially the same as those for producing the nonwoven fabric of the single-layer structure described above. As will be described in detail below.

The nonwoven fabric shown in fig. 2 includes three fiber layers 1, 2, and 3 each made of short fibers. Wherein the fibre layers 1 and 3 on both sides are high melting fibre layers, for example having a melting point above about 180 c, for example between 190 c and 230 c, preferably between 215 c and 230 c or higher. While the middle fiber layer 2 is a low melting fiber layer, e.g., having a melting point of about 115 c to 130 c or less.

The fiber layers 1, 2, 3 may be formed of the same kind of short fibers or different kinds of short fibers, for example, dacron with melting points of 130 ℃ and 230 ℃ may be selected, respectively, or dacron with melting point of 130 ℃ and polypropylene (PP) with melting point of 190 ℃ may be selected, respectively.

The types of the fiber layers 1, 2, and 3 may be determined by the filter using the non-woven fabric, and any types of short fibers may be used, such as polyester, polypropylene (PP), nylon, and acryl, and further, Polyamide (PA), viscose, acrylic, polyethylene (HDPE), polyvinyl chloride (PVC), and the like.

The invention is characterized in that the low-melting fiber layer is a solidified material, in particular having the property of being solidified after being heated and melted, so that the nonwoven fabric formed thereby is self-supporting and has form-retaining properties. The nonwoven fabric of the present invention is further characterized by excellent moldability, i.e., the nonwoven fabric can stably maintain various shapes after being molded into the shapes according to the practical use.

The melting and solidifying process of the low-melting-point fiber layer 2 may be performed as follows. After the fiber layers 1, 2, 3 are converted into a woven fabric of a raw fabric by a needle punching process or the like, the nonwoven fabric is formed by melting the fiber layer 2 having a low melting point into a molten state at a given temperature lower than the melting point of the fiber layer having a high melting point but higher than the melting point of the fiber layer having a low melting point, entangling the fibers having a high melting point, and then rapidly cooling the fibers, so that the fiber layer 2 having a low melting point is melted and then cooled, a part of the fiber layer 2 penetrates into the fiber layers 1 and 3, and the fiber layer 2 is solidified into a hard material after cooling. The Shore A hardness of the non-woven fabric can reach 50-80 degrees measured by an A-type Shore durometer, and the hardness is a physical measurement mode of the compression deformation degree or the puncture resistance of a substance.

The hardness of the nonwoven fabric of the present invention depends on the proportion of low-melting-point fibers in the nonwoven fabric in the case where the nonwoven fabric has the same density. The higher the proportion of low-melting-point fibers, the greater the stiffness of the resulting nonwoven fabric. Generally, the low-melting-point fiber accounts for 20-50 wt% of the whole nonwoven fabric material, and the high-melting-point fiber accounts for 50-80 wt% of the whole nonwoven fabric material. Preferably, the low-melting-point fibers account for 30% -40% of the whole nonwoven material, and the high-melting-point fibers account for 60% -70% of the whole nonwoven material.

The nonwoven fabric of the invention has a high stiffness and can therefore be self-supporting, i.e. the nonwoven fabric can stand on its own without any support or can be placed on two support points without significant bending. In particular, the nonwoven fabric of the invention, when used to manufacture filter cartridges up to 2 meters in length, is sufficiently rigid to maintain the form of the cartridge without any support when placed upright or laid flat. When the nonwoven fabric of the present invention is installed in a filter, the support frame may be omitted from the filter. As shown in fig. 4, in the filter using the non-woven fabric of the present invention, there is no need to install any supporting member, in which the non-woven fabric 20 can support its own weight as well as the weight of the end portion. In the prior art, it has not been found that the nonwoven fabric made of short fibers can support its own weight because the nonwoven fabric made of short fibers is soft and not sufficiently hard.

The nonwoven fabric of the present invention is pleatable because of its excellent hardness, for example, 50 to 80 degrees as measured by a shore a durometer. This is an important feature of the needle punched non-woven fabric (felt) of the present invention, which is not possible with the existing needle punched non-woven fabrics. Fig. 3 shows that the needle-punched non-woven fabric of the present invention is manufactured in a corrugated shape, and can be used for a corrugated filter to increase a filtering area without any supporting frame.

In the nonwoven fabric of this embodiment, the low-melting-point fiber layer functions as a support layer since it is formed by being solidified after being melted; and the high melting point fiber layer is not melted during the processing of the non-woven fabric and still maintains the basic characteristics of the non-woven fabric, such as filtration, air permeability and adsorptivity, without being changed, so that the high melting point fiber layer can be used as a filter medium of a filter.

Another important feature of the needle punched nonwoven fabric of the present invention is that the nonwoven fabric is able to maintain its molded shape or configuration well after it has been molded into any shape or configuration. Owing to their very good formability, the needle-punched nonwoven fabric according to the invention finds wide application in many fields, for example in the application of filter devices, where it can be moulded into filter elements of various shapes, as desired. As will be described in detail below.

A further important feature of the needle-punched nonwoven fabric of the invention is that the nonwoven fabric has a very high compressive strength, even if wrinkles are formed in the nonwoven fabric. The invention has been tested by immersing the pleated needle-punched non-woven fabric in water for 24 hours, taking out and putting on a plane to roll the pleated non-woven fabric back and forth by using an automobile of more than 200 tons. As a result, it was found that the nonwoven fabric had wrinkles that maintained their shape and did not collapse. This shows that the needle-punched non-woven fabric of the present invention has high impact and pressure resistance even if it is pleated, can withstand repeated blows and flushes of pulse air flow or liquid and impacts from clean gas or liquid for a long period of time, and is useful as a material for filter media to maintain the dimensional stability of the filter media.

The gram weight of the non-woven fabric is generally 150-2000g/m²Within the range. For example, a grammage of about 500g/m is to be made²The nonwoven fabric of (2) may be a nonwoven fabric having a grammage of 170g/m²The gram weight of the two layers of high-melting-point short fibers 1 and 3 is 160g/m²The low-melting-point short fiber layer 2 is sandwiched. After the product is prepared, the high-melting-point fiber layers 1 and 3 on the two sides are relatively soft and have strong dust collection capacity; the middle low-melt fiber layer 2 is relatively stiff and serves as a support, and the three layers of the blank may be joined to each other by processes such as needling, hydroentangling, and the like. As is well known to those skilled in the art, nonwoven fabrics of the same grammage can be made into fabrics of different densities as required by the application.

In addition, additives such as a crystal nucleus agent, a delustering agent, a pigment, an antibacterial agent, a flame retardant, a hydrophilic agent, and the like may be added to the nonwoven fabric of the present invention to further enhance the performance or satisfy a specific use. The nonwoven fabric product of the present invention may also be printed with a pattern using a device such as an embossing roll.

The method for producing the nonwoven fabric of the present invention is described below. Generally, the method for producing a nonwoven fabric of the present invention includes a pretreatment step for producing a raw fabric and a post-treatment step for treating the raw fabric.

The pretreatment step includes the following steps. First, a short fiber material in the form of cotton is carded in a carding machine, and then laid in a web-like planar layer on a web laying machine, the fiber layer may be a single layer containing only high-melting-point short fibers and low-melting-point short fibers which are uniformly mixed, or may be a layer of high-melting-point short fibers and a layer of low-melting-point short fibers which are alternately laid, for example, two, three or more layers. The web-like planar fibrous layer is then subjected to a process such as needling. The needled fibrous material has been formed into a nonwoven blank which is then wound into rolls for use.

The post-processing step comprises the steps of: and putting the grey cloth into an oven, and carrying out heat treatment on the grey cloth at a temperature higher than the melting point of the low-melting-point short fiber layer and lower than the melting point of the high-melting-point short fiber layer to melt the low-melting-point short fiber layer. After the heat treatment, the low-melting fibers are melted and become molten to entangle the high-melting fibers, while the high-melting fibers are not melted, so that the structure of the raw fabric becomes such that the melted low-melting fibers are sandwiched between the unmelted high-melting fibers. And then cooling the heat-treated grey cloth to solidify the molten low-melting-point short fiber layer, thereby obtaining the non-woven fabric.

Preferably, the high melting fibers have a melting point above about 180 ℃, such as between 190 ℃ and 230 ℃, preferably between 215 ℃ and 230 ℃, or higher. And the low-melting fiber has a melting point of between about 115 ℃ and 130 ℃ or less, in which case the heat treatment temperature may be about 140 ℃ to 150 ℃, and the cooling temperature may be about 10 ℃ to 15 ℃.

In the heat treatment, hot air is preferably blown perpendicularly to the upper and lower surfaces of the raw fabric so that the hot air can directly penetrate through the raw fabric to heat the low-melting-point fiber layer inside. The cooling of the blank is preferably rapid, for example, a cooling roll weighing, for example, 200kg may be pressed down on the blank by its own weight while cooling the blank, or the cooling roll may be pressed down on the blank by an oil pressure when the grammage of the nonwoven is large, so that the cooling is faster, for example, the nonwoven may be cooled from about 150 ℃ to about 15 ℃ in about 5 to 15 seconds, to make the resulting nonwoven more dense.

The nonwoven fabric of the present invention may then be pleated, if desired, for example, if desired to form a filter element of a pleated filter, to form a corrugated nonwoven fabric, as shown in fig. 3.

The shore a hardness of the nonwoven fabric of the present invention obtained according to the above manufacturing method may be as high as 50 to 80 degrees, as measured by a shore a durometer, sufficient to support its own weight or to be pleated or the like.

In addition to the needling process, the pre-treatment step may also employ hydroentangling, thermal bonding, air-laying, wet or stitch-bonding processes to form the blank.

The spunlace process is to spray high-pressure fine water flow onto one or more layers of fiber webs to entangle the fibers with each other, so that the fiber webs are reinforced and have certain strength.

The thermal bonding non-woven fabric is formed by adding fibrous or powdery hot melt bonding reinforcing materials into a fiber web, and heating, melting, cooling and reinforcing the fiber web into a fabric.

The air-laid nonwoven fabric can be called as dust-free paper and dry papermaking nonwoven fabric. It adopts the air-laid technology to open the wood pulp fiber board into single fiber state, then uses the air-laid method to make the fiber agglutinate on the net-forming curtain, then the net is consolidated into cloth.

The wet-process non-woven fabric is made up through opening the raw fibre material in water medium to obtain single fibre, mixing different fibre materials to obtain fibre suspension pulp, delivering the suspension pulp to net-forming mechanism, and wet-forming and solidifying.

The needle-punched non-woven fabric is one of dry non-woven fabrics, and the needle-punched non-woven fabric is formed by reinforcing a fluffy fiber web into a fabric by utilizing the piercing effect of a needle.

A stitchbonded nonwoven is one type of dry-laid nonwoven, and the stitchbonding process utilizes a warp-knit loop structure to reinforce a web, a layer of yarn, a nonwoven material (e.g., a plastic sheet, a plastic foil, etc.), or a combination thereof, to form the nonwoven.

These process steps for forming the blank are known per se and will not be described in detail here.

The needle-punched non-woven fabric of the present invention has excellent filtering performance, air permeability, adsorptivity, hardness, formability, light weight, capability of withstanding repeated spraying and washing with cleaning gas or liquid, capability of being pleated, etc., and is therefore particularly suitable for use in the manufacture of filter media.

Fig. 4 shows a cartridge filter 100 using the needle-punched non-woven fabric of the present invention as a filter medium. Specifically, after the above-described manufacturing process of the nonwoven fabric of the present invention is completed, the nonwoven fabric 20 of the present invention may be pleated to form pleats 22, bent into a cylindrical shape having both ends open, and then installed between the two end caps 24, 26 of the filter such that the fiber layer formed of the high melting point fibers faces the air flow or fluid to be filtered, thereby forming the filter shown in fig. 4. In this embodiment, the end caps 24, 26 are made of a metal, such as stainless steel, and are annular in shape. Because of the higher stiffness of the nonwoven fabric of the present invention, no support frame for the nonwoven fabric 20 is required in the filter of fig. 4, which on the one hand saves the material cost of the filter and the operation cost of replacing the filter, and on the other hand, simplifies the installation process between the nonwoven fabric and the filter end covering. The cartridge filter using the nonwoven fabric of the present invention can save a large amount of cost compared to the existing filter. Unlike the pleats formed by the spun-bonded nonwoven fabric, the pleats of the nonwoven fabric of the present invention are not easily collapsed, so that the filter area of the cartridge filter can be maintained, and if the span between the pleats is sufficiently large, the bridging of dust can be reduced, and the filter can be easily washed and cleaned.

Figure 5 shows a further modification to the cartridge filter shown in figure 4. In particular, the filter 200 shown in fig. 5 differs from the cartridge filter 100 shown in fig. 4 in that the two end caps 34, 36 are moulded from a needle-punched non-woven fabric of the invention and the surface profile of the end caps is moulded to correspond to the cross-sectional shape of the pleat-shaped filter cartridge, so that the humps 33 and pockets 35 formed by the end cap profile are flush with the humps of each pleat in the filter cartridge and the grooves formed between adjacent pleats. This has the advantage that dust adhering to the filter cartridge will slide down the flutes of the filter cartridge and pockets of the end cap and will not accumulate on the end cap, thereby reducing the operational cost of cleaning the end cap and filter cartridge.

Alternatively, a PTFE film (polytetrafluoroethylene film) or an acrylic coating may be applied to the surface of the needle-punched nonwoven fabric of the present invention to increase the smoothness of the nonwoven fabric. This is advantageous for dust attached to the filter cartridge to fall off and clean.

Two different bag filters are shown in fig. 6 and 7. Conventional bag filters typically include a flexible filter bag and a support structure formed as a basket inside the bag to prevent the bag from collapsing due to gas flowing from outside the bag into the bag. When installing a conventional bag filter, it is necessary to first secure the filter bag in place and then place a basket-like support structure adapted to the size of the filter bag into the filter bag. Therefore, the installation and replacement of conventional bag filters is extremely labor intensive.

Fig. 6 shows a bag filter 300 using the nonwoven fabric of the present invention as a filter medium, and as shown, the bag filter 300 includes a filter bag 42 made of the needle-punched nonwoven fabric of the present invention. The filter bag 42 is pleated to form pleats 44 and then bent into a cylindrical shape, or a single pleat is formed by molding using the moldability of the needle punched non-woven fabric of the present invention and then bent into a cylindrical shape. The bottom end of the filter bag is sealed and the top end is a press buckle belt type opening end 46 for fixing the filter bag and allowing the filtered clean gas to flow out. The bag filter 300 eliminates the basket support structure required for the conventional bag filter because the nonwoven fabric of the present invention has high hardness and can maintain its shape after compression molding. Therefore, the material cost of the supporting structure and the operation cost of replacing and maintaining the filter are saved, the installation and replacement of the filter are greatly simplified, and the labor intensity is reduced.

Fig. 7 shows another variant of a bag filter. As shown, the bag filter 400 includes a cylindrical body, a sealed end and an open end, the cylindrical body and the sealed end being integrally molded from the needle-punched non-woven fabric of the present invention. Since the nonwoven fabric of the present invention can maintain its shape or configuration after compression molding and has high hardness, the bag filter 400 formed therefrom can have dimensional stability against high impact force.

Fig. 8 to 11 show CGR plate filters made of the needle-punched non-woven fabric of the present invention. A conventional CGR (Caulked, Gasketed, Recessed) plate filter includes an embedded support plate and filter cloths fixed to both sides of the support plate. Wherein, the periphery of the bearing plate forms an annular groove, and the center of the bearing plate is provided with a through hole; the edge of the filter cloth is sewed into the sealing ring, when the filter cloth is fixed, the filter cloth needs to penetrate through the central through hole from one side of the supporting plate and then be unfolded to be tightly attached to the surface of the supporting plate, and then the edge sewed with the sealing ring is forcibly embedded (for example, knocked in by a hammer) into the peripheral annular groove of the supporting plate, so that the capillary leakage phenomenon is effectively prevented. The manufacture, installation and replacement of the conventional CGR plate filter involve sewing the edges of the filter cloth, sewing the seal ring into the groove, inserting the seal ring into the groove, passing the filter cloth through the central through hole of the support plate and then expanding the filter cloth, and the like, and the operations involve huge manpower and time, are not only tedious and time-consuming, and have high labor intensity, but also greatly increase the cost and the production period. In addition, when the filter cloth is mounted on the embedded support plate, the filter cloth is easily damaged and cannot be used.

Fig. 8 to 11 show a CGR panel filter 500 using the needle-punched non-woven fabric of the present invention, which includes a first filter element 52, a second filter element 54, and an embedded supporting plate 56 having a central through-hole 57 interposed therebetween, wherein the first and second filter elements 52, 54 and the embedded supporting plate 56 are integrally molded with the needle-punched non-woven fabric of the present invention, respectively. The embedded support plate 56 is substantially the same structure as the support plate of a conventional CGR plate filter. The first filter element 52 and the second filter element 54 each include a filter element body 51, a hollow cylindrical core 53 formed at the center of the filter element body, and a semicircular flange 55 formed at the periphery of the filter element body, wherein the cylindrical core 53 and the flange 55 protrude outward on the same side of the filter element body. However, the diameter of the hollow cylindrical core of the second filter element is slightly smaller than that of the hollow cylindrical core of the first filter element, so that the hollow cylindrical core of the second filter element is just inserted into and fixed in the hollow cylindrical core of the first filter element in an embedded mode. The filter element body 51, the cylindrical core 53 and the circular flange 55 are integrally molded from the needle-punched non-woven fabric of the present invention in this embodiment.

The cylindrical core of the first filter element 52 is shaped and dimensioned to extend just past the central through bore 57 of the insert support plate 56 and the cylindrical core of the second filter element 54 is shaped and dimensioned to extend just past the cylindrical core of the first filter element and to intermesh together. The semi-circular flanges of the first and second filter elements 52, 54 are shaped and dimensioned to fit snugly within the groove 58 formed along the periphery of the embedded support plate and remain secured together.

As described above, since the nonwoven fabric of the present invention has excellent hardness and moldability, the first filter element 52, the second filter element 54, and the embedded support plate 56, which are molded by press, can stably maintain their respective forms. When the CGR panel filter 500 is installed, the cylindrical core of the first filter element 52 is simply inserted through the central opening 57 from the side of the support plate 56 and the semicircular flange 55 is then pressed into the annular recess 58 of the support plate 56 with a slight force. The cylindrical core of second filter element 54 is then passed from the other side of support plate 56 through central throughbore 57 and the cylindrical core of first filter element 52 so that the cylindrical core of second filter element 54 just engages the cylindrical core of first filter element 52, and then circular flange 55 of second filter element 54 is pressed into annular recess 58 on the other side of support plate 56 with a slight amount of force. The installation process can be seen in fig. 10 and 11.

It can be seen that the CGR panel filter 500 of the present invention eliminates the need for sewing the edges of the filter cloth, sewing in the seal ring and using a hammer to engage the groove, re-expanding the filter cloth through the central through hole of the support plate, and the like, which are required in conventional CGR panel filters, greatly reducing labor intensity and reducing the cost of operating, installing, and replacing the filter. And the installation of the filter elements on both sides is independent, so the filter elements on either side can be replaced or treated at will.

Fig. 12 and 13 show a sector-shaped filter unit constituting a rotary disc filter using a needle-punched non-woven fabric of the present invention. As is well known to those skilled in the art, rotary disc filters are commonly used in heavy industries such as iron mining, coal mining, etc. for processing liquid-solid separation operations, and are interconnected into a disc shape by a plurality of fan-shaped filter elements. Each sector-shaped filter element comprises a filter pocket and a support plate placed inside the filter pocket for supporting the filter pocket, said support plate having a plurality of grooves for guiding the filtrate towards the filter outlet. The support plates of the prior art are generally made of metal and are very bulky, resulting in extreme effort to install, repair, move and replace the sector-shaped filter elements.

Since the needle-punched non-woven fabric of the present invention has the characteristics of light weight, high hardness, high strength, easy molding, shape retention, etc., the non-woven fabric of the present invention is molded into a support plate, the weight of the support plate can be remarkably reduced but the hardness thereof is sufficient to support a filter bag, and the molded shape thereof can be maintained to provide sufficient pressure resistance. Likewise, the support plate may be profiled to form a plurality of grooves along its longitudinal direction to direct filtrate through the grooves towards the filtrate outlet, as shown in fig. 12. Generally, the weight of the support plate made of the needle-punched non-woven fabric of the present invention is about 1/3 to 1/4 lighter than that of the conventional metal support plate, which is advantageous in reducing the labor intensity of handling the support plate.

According to another modification of the present invention, a first filtering wall 62 and a second filtering wall 64 opposite to the first filtering wall are made of the needle-punched non-woven fabric of the present invention, and a filtrate chamber 66 is formed between the first and second filtering walls 62, 64 to receive a filtrate flowing through the first and second filtering walls, as shown in fig. 13. In this embodiment, the support plate 61 accommodated in the filtrate chamber is also molded from the needle-punched non-woven fabric of the present invention as shown in fig. 12, and has a shape in which a plurality of grooves 63 are formed in a radial direction of the support plate 61 to guide the filtrate to flow through the grooves toward the filtrate outlet 65.

The first and second filter walls 62, 64 are shaped such that they engage each other to form a closed chamber. Referring to fig. 13, an example of the first and second filter walls 62, 64 engaging one another to form a closed chamber is shown. As shown, the first and second filtering walls 62, 64 each have a vertical surface 67, an upper side 68 and a lower side 69 extending horizontally to the same side along the upper and lower ends of the vertical surface 67, respectively. Wherein the upper and lower sides 68, 69 of the first and second filter walls 62, 64 are sized and shaped to snap fit together just tightly without loosening. When the fan-shaped filter element is installed, the first filter wall and the second filter wall are clamped and fixed together by only clamping the first filter wall and the second filter wall at two sides of the supporting plate and then slightly exerting force to form a filter chamber.

The nonwoven fabric having high hardness of the present invention, the method for producing the same, and the filter using the nonwoven fabric of the present invention have been described above in preferred embodiments. Various improvements and/or modifications to the present invention may be made by those skilled in the art in light of the teachings of the specification, and such improvements and/or modifications are intended to be included within the scope of the present invention as defined in the appended claims.

Claims

1. A nonwoven fabric made of at least one low-melting-point short fiber and at least one high-melting-point short fiber of the same kind or different kinds, the nonwoven fabric being a needle-punched nonwoven fabric having a stiffness sufficient to enable the nonwoven fabric to be self-supporting and to have form-retaining properties, and being moldable, i.e., capable of being molded into a desired shape and capable of stably retaining the form of the desired shape under an external pressure during use after being molded into the desired shape, the nonwoven fabric having a grammage of 500-²In this range, the nonwoven fabric is a single-layer fiber layer formed by uniformly mixing the low-melting-point short fibers and the high-melting-point short fibers.

2. The nonwoven fabric according to claim 1, wherein the low-melting-point short fibers are formed by entangling high-melting-point fibers by heating and melting them into a molten state, followed by rapid cooling and solidification.

3. A nonwoven fabric according to claim 1, characterized in that the high melting point staple fibers have a melting point in the range of 180 ℃ to 230 ℃ and the low melting point staple fibers have a melting point in the range of 115 ℃ to 130 ℃.

4. Nonwoven according to claim 1, characterised in that the low-melting or high-melting staple fibres are selected from the group consisting of polyester, polypropylene, acrylic, polyamide, viscose, acrylic, polyethylene and polyvinyl chloride.

5. A nonwoven fabric according to claim 4, characterized in that the polyester is Dacron.

6. Nonwoven according to claim 1, characterised in that the shore a hardness of the nonwoven is up to 50-80 degrees.

7. Nonwoven fabric according to claim 1, characterised in that the nonwoven fabric is pleatable.

8. The nonwoven fabric according to claim 1, characterized in that the low-melting staple fibers are 20 to 50% by weight of the nonwoven material as a whole and the high-melting staple fibers are 50 to 80% by weight of the nonwoven material as a whole.

9. The nonwoven fabric according to claim 8, characterized in that the low-melting fibers are 30 to 40% by weight of the nonwoven material as a whole and the high-melting staple fibers are 60 to 70% by weight of the nonwoven material as a whole.

10. Nonwoven fabric according to claim 1, characterized in that it is obtained in the following manner: and a step of forming a raw fabric from the low-melting point and high-melting point fibers, and then subjecting the raw fabric to a heat treatment at a temperature lower than the melting point of the high-melting point fibers but higher than the melting point of the low-melting point fibers to melt the low-melting point fibers into a molten state and entangle the high-melting point fibers, followed by rapid cooling.

11. A nonwoven fabric made of at least one low-melting-point short fiber and at least one high-melting-point short fiber of the same kind or different kinds, the nonwoven fabric being a needle-punched nonwoven fabric having a stiffness sufficient to enable the nonwoven fabric to be self-supporting and to have form-retaining properties, and being moldable, i.e., capable of being molded into a desired shape and capable of stably retaining the form of the desired shape under an external pressure during use after being molded into the desired shape, the nonwoven fabric having a grammage of 500-²Within the scope, the nonwoven fabric comprises at least two layers of high-melting-point short fibers and one layer of low-melting-point short fibers sandwiched between each two layers of high-melting-point short fibers.

12. The nonwoven fabric according to claim 11, characterized in that the low-melting-point short fibers are formed by entangling high-melting-point fibers by being heated and melted into a molten state, followed by rapid cooling and solidification.

13. A nonwoven fabric according to claim 11, characterized in that the high melting point staple fibers have a melting point in the range of 180 ℃ to 230 ℃ and the low melting point staple fibers have a melting point in the range of 115 ℃ to 130 ℃.

14. Nonwoven according to claim 11, characterised in that the low-melting or high-melting staple fibres are selected from the group consisting of polyester, polypropylene, acrylic, polyamide, viscose, acrylic, polyethylene and polyvinyl chloride.

15. Nonwoven fabric according to claim 14, characterized in that the polyester is dacron.

16. Nonwoven fabric according to claim 11, characterised in that the nonwoven fabric has a shore a hardness of up to 50-80 degrees.

17. Nonwoven fabric according to claim 11, characterised in that the nonwoven fabric is pleatable.

18. The nonwoven fabric according to claim 11, characterized in that the low-melting staple fibers are 20 to 50% by weight of the nonwoven material as a whole and the high-melting staple fibers are 50 to 80% by weight of the nonwoven material as a whole.

19. The nonwoven fabric according to claim 18, characterized in that the low-melting fibers represent 30 to 40% by weight of the nonwoven material as a whole and the high-melting staple fibers represent 60 to 70% by weight of the nonwoven material as a whole.

20. Nonwoven fabric according to claim 11, characterized in that the nonwoven fabric is obtained in the following manner: and a step of forming a raw fabric from the low-melting point and high-melting point fibers, and then subjecting the raw fabric to a heat treatment at a temperature lower than the melting point of the high-melting point fibers but higher than the melting point of the low-melting point fibers to melt the low-melting point fibers into a molten state and entangle the high-melting point fibers, followed by rapid cooling.

21. A filter, characterized in that a nonwoven fabric according to one of claims 1 to 20 is used as a material for the filter medium of the filter.

22. A filter according to claim 21, which is a cartridge filter, characterized in that the nonwoven fabric forms a cylindrical filter cartridge, which filter cartridge is self-supporting.

23. The filter of claim 22, wherein the filter cartridge is formed in a pleated shape.

24. A filter according to claim 23, further comprising an end cap made of a non-woven fabric according to any one of claims 1 to 20, the surface profile of the end cap being moulded to correspond to the cross-sectional shape of the pleated filter cartridge.

25. A filter according to any one of claims 21 to 24, characterised in that a PTFE membrane or acrylic coating is applied to the surface of the non-woven fabric.

26. A filter according to claim 21, which is a bag filter, characterized in that the nonwoven fabric is moulded into a filter pocket of the bag filter, which filter pocket is self-supporting.

27. A filter according to claim 21, which is a bag filter, characterized in that the nonwoven fabric is rolled after pleating into a filter pocket of the bag filter, which filter pocket is self-supporting.

28. The filter of claim 21, which is a CGR insert plate filter comprising a first filter element, a second filter element opposite the first filter element, and an insert support plate having a central through hole sandwiched therebetween, wherein the first and second filter elements are molded from the non-woven fabric.

29. The filter of claim 28, wherein the first and second filter elements each comprise a filter element body, a cylindrical core formed at the center of the filter element body, and a flange formed at the periphery of the filter element body, the cylindrical core and the flange protruding outward on the same side of the filter element body, and the filter element body, the cylindrical core, and the flange are integrally molded from the nonwoven fabric;

the cylindrical core of the first filter element is shaped and dimensioned to extend just past the central through-hole of the insert support plate, and the cylindrical core of the second filter element is shaped and dimensioned to extend just past the cylindrical core of the first filter element and to intermesh together;

the flanges of the first and second filter elements are shaped and dimensioned to fit snugly within a recess formed along the periphery of the embedded support plate.

30. The filter according to claim 21, which is a rotary disc filter formed by connecting a plurality of fan-shaped filter elements to each other, characterized in that the fan-shaped filter elements each comprise a first filter wall made of the nonwoven fabric and a second filter wall made of the nonwoven fabric and opposed to the first filter wall, a filtrate chamber being formed between the first and second filter walls to accommodate filtrate flowing through the first and second filter walls.

31. A filter as claimed in claim 30, wherein said fan-shaped filter element further comprises a support plate received in said filtrate chamber, wherein said support plate is molded from said nonwoven fabric and is contoured to define a plurality of grooves extending radially of said support plate for directing filtrate through said grooves toward a filtrate outlet.

32. A filter according to claim 30 or 31, wherein the first and second filter walls are shaped such that they engage each other to form a closed chamber.

33. A rotary disc filter comprising a plurality of support plates attached to each other and filter bags for enclosing the support plates, characterized in that the support plates are molded from the nonwoven fabric according to one of claims 1 to 20.

34. The filter of claim 33, wherein the support plate has an outer shape defining a plurality of grooves along a radial direction thereof for directing filtrate through the grooves toward the filtrate outlet.

35. A method of making the nonwoven fabric of any of claims 1-10, comprising the steps of:

1) putting the cotton-shaped short fibers with high melting point and the short fibers with low melting point into a cotton mixing box according to the required proportion to uniformly mix the short fibers with high melting point and the short fibers with low melting point to prepare single-layer fibers;

2) conveying the mixed fibers to a carding machine for carding;

the method is characterized by further comprising the following steps:

36. The manufacturing method according to claim 35, characterized in that during the heat treatment, the low-melting-point short fibers are melted and become a molten state to entangle the high-melting-point fibers, while the high-melting-point short fibers are not melted.

37. The manufacturing method according to claim 35 or 36, characterized in that the melting point of the high-melting-point short fiber is 180 ℃ to 230 ℃, the melting point of the low-melting-point short fiber is 115 ℃ to 130 ℃, the temperature of the heat treatment is 140 ℃ to 150 ℃, and the temperature of the cooling is 10 ℃ to 18 ℃.

38. The manufacturing method according to claim 35 or 36, wherein hot air is blown to upper and lower surfaces of the raw fabric in a vertical direction to directly penetrate the raw fabric to heat the low melting point fiber inside.

39. A method according to claim 35 or 36, characterised in that the blank is rapidly cooled by pressing the chill roll down on the blank under its own weight or by means of oil pressure.

40. The method according to claim 35 or 36, wherein the nonwoven fabric is pleated to form a pleated -shaped nonwoven fabric.

41. A method of making the nonwoven fabric of any of claims 11-20, comprising the steps of:

1) alternately putting the cotton-shaped short fibers with high melting point and the short fibers with low melting point into a cotton mixing box according to the required proportion to respectively and uniformly mix the short fibers with high melting point and the short fibers with low melting point to prepare multilayer fibers;

2) conveying the mixed fibers to a carding machine for carding;

the method is characterized by further comprising the following steps:

42. The manufacturing method according to claim 41, characterized in that during the heat treatment, said low-melting-point short fibers are melted and become a molten state to entangle the high-melting-point fibers, while said high-melting-point short fibers are not melted, whereby the structure of said raw fabric becomes a structure in which a layer of the melted low-melting-point short fibers is sandwiched between layers of the non-melted high-melting-point short fibers.

43. The manufacturing method according to claim 41 or 42, characterized in that the melting point of said high melting point short fiber is in the range of 180 ℃ to 230 ℃, the melting point of said low melting point short fiber is in the range of 115 ℃ to 130 ℃, the temperature of said heat treatment is in the range of 140 ℃ to 150 ℃, and the temperature of said cooling is in the range of 10 ℃ to 18 ℃.

44. The manufacturing method according to claim 41 or 42, wherein hot air is blown to the upper and lower surfaces of the raw fabric in a vertical direction to directly penetrate the raw fabric to heat the low melting point fiber layer inside.

45. A method according to claim 41 or 42, characterized in that the blank is rapidly cooled by pressing the chill roll down on the blank under its own weight or by means of oil pressure using a chill roll.

46. The method according to claim 41 or 42, wherein the nonwoven fabric is pleated to form a pleated -shaped nonwoven fabric.