HK1203575B - Needle-punched non-woven fabric, manufacturing method thereof and filter and sound absorbing material formed thereby - Google Patents

Description

Needle-punched nonwoven fabric, method for producing same, and filter and sound absorbing material formed from same

Technical Field

The present invention relates to a nonwoven fabric having good hardness, stiffness, moldability and compressive strength, a method for producing the same, a filter formed from the nonwoven fabric as a material for producing a filter element, and use as a sound-absorbing material.

Background

A nonwoven fabric, also called a nonwoven fabric, is a woven fabric formed without spinning a woven fabric, has good filterability, air permeability and adsorptivity, and is very suitable for use as a filter element of a filter.

The existing needle-punched non-woven fabrics (felt) are generally soft in texture 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, there has not been disclosed in the prior art a needle-punched non-woven fabric (felt) which is high in rigidity so that it can be self-supported with form-retaining property and moldability and can be 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.

PCT international patent application PCT/CN2011/071371, which is filed by the applicant on 28/2/2011, discloses a nonwoven fabric made of at least two types of staple fibers including low-melting-point staple fibers and high-melting-point staple fibers, a method of manufacturing the same, and a filter formed of the same. 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 has sufficient stiffness to be self-supporting and form-retaining, and is moldable. It has excellent hardness or rigidity or stiffness, excellent moldability, and very high compressive strength. In addition, the needle-punched non-woven fabric is manufactured into a corrugated shape, and can be used for a filter with the corrugated shape to increase the filtering area without any supporting frame.

However, the needle-punched non-woven fabric in the PCT international patent application needs to be manufactured by using two types of short fibers with different melting points, and requires more materials, and has a relatively complicated manufacturing process and higher cost.

It is known that sound often echoes in indoor spaces, for example, hard walls and wide spaces (such as auditoriums, classrooms, stadiums, movie theaters, etc.) generate reflected noise due to high echo, so that the sound is overlapped or mixed up. To eliminate this phenomenon so as to make the sound clearer, it is necessary to provide a sound absorbing material on the wall surface or ceiling surface to reduce the generation of echo. The sound absorbing material is a porous and air permeable material such as glass fiber wool, rock wool, sponge, foam, and the like. However, glass fibers are harmful to human bodies and the environment and are easily weathered, resulting in reduced sound absorption performance and short service life. Rock wool and sponge have low sound absorption, are easily deformed and flammable, and emit toxic gases during combustion. Therefore, there is a need for a sound-absorbing material having high sound-absorbing performance, flame retardancy, stable form, light weight, and the like.

Disclosure of Invention

It is an object of the present invention to provide a nonwoven fabric that is easy and inexpensive to manufacture to overcome the disadvantages of the prior art, yet maintains good stiffness, rigidity, stiffness and formability, and has a high compressive strength sufficient for molding into self-supporting filter elements and the like in a variety of configurations.

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 a single kind of short fibers or different kinds of short fibers having the same or close melting points, preferably a single kind of short fibers having a single melting point. The nonwoven fabric is still sufficiently stiff to be self-supporting and form-retaining, and is moldable.

In theory, staple fibers of various melting points may be suitable for use in the present invention, such as polyester, polypropylene, nylon, acrylic, nylon, viscose, acrylic, polyethylene, and polyvinyl chloride. In practice, however, since the operating temperature of the products made of said non-woven fabric, such as filters, is generally room temperature (25 ℃) or up to several tens of degrees celsius or even 100 ℃, the melting point of the staple fibres used for making said non-woven fabric generally needs to be above 80 ℃ or 100 ℃.

Preferably, the staple fiber is polypropylene (PP) having a melting point of about 130 ℃. Polypropylene is a crystalline polymer and although its various crystalline forms have melting points of about 150 c to 176 c, the actual staple fiber product may be, for example, a random copolymerized polypropylene with a slightly lower melting point, which may be about 130 c.

Preferably, the nonwoven fabric is obtained in the following manner: after the short fibers are formed into a raw fabric, the raw fabric is subjected to a heat treatment at a temperature higher than the melting point of the short fibers for a short time to melt a part of the short fibers into a molten state and entangle the remaining part of the short fibers which are not melted, and then rapidly cooled to form the yarn. The remaining steps may be substantially the same as the manufacturing steps described in PCT/CN2011/071371 above.

For short fibers of polypropylene, the temperature of the heat treatment is, for example, 130 ℃ to 160 ℃ or 180 ℃ to 200 ℃ respectively, and the short heat treatment is to control the residence time of the greige cloth in the oven, for example, to pass the greige cloth through the oven at the heat treatment temperature at a rate of about 4 to 5 m/min, for example, to heat the greige cloth at a rate of about 30 seconds per square meter of greige cloth, thereby to melt a portion of the short fibers in the greige cloth, the melted portion constituting about 30 to 80%, preferably 60 to 70%, of the greige cloth; and then the grey fabric is rapidly cooled to solidify and harden the grey fabric into the single-melting-point non-woven fabric.

When the single melting point nonwoven fabric is molded into various shapes, the nonwoven fabric may be heated slightly at a temperature lower than the melting point of the short fibers, for example, 100 ℃ for polypropylene, to soften it but not melt, so that it can be easily molded into a desired shape.

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

The nonwoven fabric of the present invention is particularly suitable for use as a filter element of gas-solid and liquid-solid separation filters. The invention therefore also provides a filter, the non-woven fabric of the invention being used as a material for the filter element of which the filter is made, the filter element being self-supporting without the use of any supporting structure.

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

1) putting short fibers of the same kind or different kinds with the same or close melting points in a cotton-shaped cotton mixing box to be uniformly mixed to prepare a layered fiber layer, wherein the short fibers can be single short 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) subjecting the blank to a heat treatment at a temperature above the melting point of the staple fibers for a short period of time to melt a portion of the staple fibers, the melted staple fibers becoming molten and entangling with another portion of the staple fibers which is not melted, wherein the proportion of the molten portion of the fibers is about 30-80%, preferably 60-70%, of the blank;

6) and cooling the heat-treated grey fabric to solidify the molten short fibers to obtain the non-woven fabric.

As mentioned above, the staple fiber may be polypropylene having a melting point of about 130 ℃ or 150 ℃ to 176 ℃, and the temperature of the heat treatment may be, for example, 130 ℃ to 160 ℃, or 180 ℃ to 200 ℃, respectively. In order to achieve the fusion of one part of the fibers with another part of the fibers remaining unmelted, the blank is subjected to a heat treatment as follows: the blank is passed through the oven at the heat treatment temperature at a rate, for example, of about 4 to 5 meters per minute, i.e., the blank is heated at a rate of about 30 seconds per square meter of blank, thereby melting about 30 to 80 weight percent, preferably 60 to 70 weight percent, of the staple fibers in the blank.

In the heat treatment process, hot air can be 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 can obtain a better heating effect.

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

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.

The Shore A hardness of the non-woven fabric can reach 50-80 degrees. The grammage of the nonwoven fabric is 250 to 3000g/m²Within the range.

It has been found that the nonwoven fabric according to the invention has a stiffness comparable to that of the nonwoven fabric produced in the above-mentioned international patent application PCT/CN2011/071371 using different staple fiber layers with high and low melting points, and is sufficient for use in products such as self-supporting filters, and can be pleated, for example. Compared with the prior art, the invention adopts the short fiber with one melting point, so that the material cost and the manufacturing cost can be obviously reduced, and the manufacturing time can be saved.

Detailed Description

The present invention is an improvement of the solution in PCT international patent application PCT/CN2011/071371 of the same applicant, the entire content of which is incorporated herein by reference, the following contents mainly refer to the differences from the solution in PCT/CN2011/071371, and the rest of the contents which are not specifically indicated can refer to PCT/CN 2011/071371.

The present invention relates to a nonwoven fabric made of short fibers by a method such as needle punching, which has excellent hardness or stiffness; 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.

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. Firstly, cotton-shaped short fiber materials are carded in a carding machine, and then are paved into a net-shaped plane layer in a lapping machine, wherein the fiber layer can only contain uniformly mixed single-melting-point short fibers or uniformly mixed short fibers with the same or similar melting points and of the same kind or different kinds. 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 (3) putting the grey cloth into an oven, carrying out heat treatment on the grey cloth at a temperature higher than the melting point of the short fibers, and controlling the retention time of the grey cloth in the oven to melt a part of the short fibers in the short fiber layer. The key to the manufacture of the single-melt needle-punched nonwoven fabric of the present invention is the heat treatment step, which is performed such that a part of the raw fabric becomes a molten state and another part of the raw fabric remains in an unmelted state during the heat treatment, so that after the heat treatment, the molten short fibers become a molten state and entangle the remaining unmelted short fibers, so that the structure of the raw fabric becomes such that the molten fibers are sandwiched between the unmelted fibers. The heat-treated raw fabric is then subjected to a cooling treatment to solidify the molten portion of the short fibers, thereby obtaining the nonwoven fabric of the present invention.

In a preferred embodiment, the staple fiber employed is polypropylene having a melting point of about 130 ℃ or 150 ℃ to 176 ℃, in which case the heat treatment temperature may be about 130 ℃ to 160 ℃, or 180 ℃ to 200 ℃, respectively, and the cooling temperature may be about 10 ℃ to 15 ℃. In heat treating the polypropylene blank, the blank is passed through an oven at the heat treatment temperature at a rate of about 4 to 5 meters per minute, i.e., the blank is heated at a rate of about 30 seconds per square meter of blank, whereby 30 to 80 weight percent, preferably 60 to 70 weight percent, of the staple fibers in the blank are melted, and 20 to 70 weight percent, preferably 30 to 40 weight percent, of the staple fibers remain unmelted. It will be appreciated by those skilled in the art that the residence time of the blank in the oven can be adjusted depending on the grammage of the blank and the desired hardness to be achieved.

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 inner fiber layer. 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 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, for example, about 150 ℃ to about 15 ℃ in about 5 to 15 seconds, to make the resultant nonwoven more dense.

The nonwoven fabric of the present invention may then be subjected to a pleating process to form a corrugated nonwoven fabric, as desired, for example, if it is desired to form a filter element for a pleated filter.

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.

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.

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.

The process steps for forming the blank, such as needling, hydroentangling, thermobonding, air-laying, wet or stitch-bonding, are known per se and will not be described in further detail here.

The needle-punched non-woven fabric of the present invention is particularly suitable for use as a filter medium for a filter, since it has excellent filterability, air permeability, light weight, high hardness, high strength, easy molding, shape retention, and ability to be pleated. The nonwoven fabric of the present invention was tested to maintain its shape or configuration after compression molding and to have high hardness and thus dimensional stability. When the non-woven fabric is molded into various filter elements of the filter press, the operation parts of sewing the edges of the filter cloth, sewing the sealing ring, embedding the hammer into the groove, penetrating the filter cloth through the central through hole of the support plate and then expanding the filter cloth, and the like, which are necessary for the conventional filter press, can be saved, thereby greatly reducing the 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.

As discussed above, the needle-punched non-woven fabric of the present invention has high density and porosity and good air permeability, and has excellent sound absorption effect, and thus can be used as a sound absorbing material. The needle-punched non-woven fabric of the present invention exhibits good form stability, is light in weight, can be molded into various shapes, is easy to construct, is harmless and pollution-free to human bodies and environments, and is an excellent environment-friendly sound-absorbing material.

In summary, the nonwoven fabric of the present invention can be used to replace the nonwoven fabric made of two different melting point staple fibers in PCT/CN2011/071371, has substantially the same application range, and can be used to manufacture substantially the same product.

The needle-punched non-woven fabric has the characteristics of light weight, high hardness, high strength, easy forming, shape retentivity and the like, so that various formed filter elements can be formed by compression molding of the non-woven fabric, the molded shape of the filter elements can be maintained, sufficient pressure resistance is provided, the installation and replacement operation of the filter elements is greatly simplified, and the labor intensity is reduced and the operation cost is saved. When used as sound absorbing material, the material is easy to construct, stable in sound absorbing performance and harmless to human body and environment.

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 (17)

1. A needle-punched non-woven fabric, which is made of short fibers of the same kind or different kinds having the same or close melting points, has a hardness sufficient to allow the non-woven fabric to be self-supporting and to have shape-retaining properties, and has moldability, and which can be molded into a desired shape and can retain the shape in use after molding, and has a grammage of 250-²In the range in which 30 to 80 wt% of the short fibers are heated to be meltedIn a state of entangling the remaining unmelted staple fibers.

2. Needle-punched nonwoven according to claim 1, characterized in that the nonwoven is obtained in the following manner: after the short fibers are formed into a raw fabric, the raw fabric is heat-treated at a temperature higher than the melting point of the short fibers so that 30 to 80 wt% of the short fibers are melted into a molten state to entangle the remaining unmelted short fibers, and then rapidly cooled.

3. Needle-punched nonwoven according to claim 1 or 2, characterised in that the nonwoven is made of a single-melting staple fiber.

4. A needle-punched nonwoven according to claim 3, characterised in that the staple fibres are polypropylene having a melting point of 130 ℃ or 150 ℃ to 176 ℃.

5. The needle-punched nonwoven fabric according to claim 2, characterized in that the proportion of the portion melted at the time of heat treatment in the short fiber is 60 to 70% by weight.

6. The needle-punched nonwoven as claimed in claim 1, characterized in that the shore a hardness of the nonwoven is 50 to 80 degrees.

7. The needle-punched nonwoven as claimed in claim 1, characterized in that the nonwoven is pleatable.

8. The needle-punched non-woven fabric according to claim 1 or 2, characterized in that the staple fiber is polyester, polypropylene, nylon, acrylic, viscose, acrylic, polyethylene or polyvinyl chloride.

9. A filter, characterized in that a needle-punched non-woven fabric according to one of claims 1 to 8 is used as a material for manufacturing a filter element of the filter.

10. Use of a needle-punched non-woven fabric according to one of claims 1 to 8 as sound-absorbing material.

11. A method of manufacturing a needle-punched nonwoven fabric according to any of claims 1 to 8, comprising the steps of:

1) putting short fibers with the same or different cotton-shaped melting points or similar melting points into a cotton mixing box, and uniformly mixing to prepare a single-layer or multi-layer fiber layer;

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) feeding the reticular planar fibers into a forming machine for needle punching and shaping treatment to prepare grey cloth;

the method is characterized by further comprising the following steps:

5) heat-treating the raw fabric at a temperature higher than the melting point of the short fibers to melt 30 to 80 wt% of the short fibers, the molten short fibers becoming a molten state to entangle another part of the non-molten short fibers;

6) and cooling the heat-treated grey fabric to solidify the molten short fibers to obtain the non-woven fabric.

12. A method according to claim 11, characterized in that a single melting point staple fiber is used in step 1).

13. The process according to claim 12, characterized in that said short fibers are polypropylene, having a melting point of 130 ℃ or 150 ℃ to 176 ℃, said heat treatment temperature being 130 ℃ to 160 ℃ or 180 ℃ to 200 ℃, respectively, and said cooling temperature being 10 ℃ to 18 ℃;

the heat treatment is carried out by passing the blank through an oven at the temperature of the heat treatment at a rate of 4 to 5 meters per minute, i.e. heating the blank at a rate of about 30 seconds per square meter of blank, whereby 30 to 80% by weight of the staple fibers in the blank are melted and 20 to 70% by weight of the staple fibers remain unmelted.

14. A method according to claim 13, characterized in that the proportion of the portion melted at the time of the heat treatment in the short fibers is 60 to 70% by weight, and 30 to 40% by weight of the short fibers remain in an unmelted state.

15. The method according to claim 11, wherein the heat treatment comprises heating the inner fiber layer by blowing hot air in a vertical direction to upper and lower surfaces of the raw fabric so that the hot air is directly penetrated through the raw fabric.

16. A method according to claim 11, characterized in that the blank is rapidly cooled by pressing the chill roll down on the blank in the form of its own weight or by means of oil pressure.

17. The method according to claim 11, characterized in that the nonwoven is pleated to form a pleated nonwoven.