Nonwoven fabric mat

Abstract

The present invention provides a nonwoven mat requiring a flange portion and a method for manufacturing the same. Examples of nonwoven mats requiring a flange portion include, but are not limited to, mats used to form plates for rotary contact devices (RBCs). Other applications include the formation of air filters, demisters, and floating treatment wetlands. [Solution] A nonwoven mat formed from fibers containing a first polymer material, wherein the mat includes a flange portion that is denser than the rest of the mat, and the flange portion further contains a second polymer material, the second polymer material being a thermoplastic resin having a melting point lower than that of the first polymer material.

Description

[Technical Field]

[0001] The inventions described herein relate to nonwoven mats and methods for manufacturing the same, and more particularly to mats requiring flanges. Examples include, but are not limited to, mats for forming plates used in rotary contact machines (RBCs). Other applications include air filters, demisters, and the formation of floating treatment wetlands. [Background technology]

[0002] Nonwoven fabrics are not formed by weaving, but rather by entangled fibers (or filaments). These fibers can maintain their entangled state in various ways, for example, mechanically (by forces resisting untangling of the fibers or filaments) or by bonding them at their intersecting surfaces (bonding can be achieved through thermal formation by melting or by adding chemicals such as adhesives).

[0003] These nonwoven fabric materials can be molded into a sheet structure to form a nonwoven mat.

[0004] The formation of nonwoven mats is a relatively inexpensive and mechanically simple method for producing fabrics with unique properties useful for various applications. Such mats can be manufactured by creating relatively large pockets (i.e., voids) of space between intertwined fibers. The presence of voids within the mat can give it specific physical properties, such as absorbency, elasticity, cushioning, heat insulation, sound insulation, and filtration.

[0005] The solid structural content of a mat is the volumetric solid fraction (i.e., F) vIt can be expressed as ). This is the value obtained by dividing the total volume of solid structural material in the mat by the volume of the mat. The solid structural material of the mat consists of fibers and thermal or chemical adhesives. However, adhesives may not be present. In the case of a mat composed of a single structural material, F v This can be easily determined by cutting a rectangular piece from the mat, measuring the dimensions of the piece, and then measuring its weight. v The formula is given by: F v =M / (ρLWT) (Equation 1) Here, M (kg) is the mass of the mat piece, and ρ (kg / m) is the mass of the mat piece. 3 ) is the density of the solid material, and L, W, and T are the length (m), width (m), and thickness (m) of the piece. If the solid material is fiber, its density is usually specified by the fiber manufacturer. Otherwise, the density can be easily measured using a hydrometer, as described in ISO 3507:1999.

[0006] It is relatively thick, yet at the same time has a relatively low F v An example of an existing mat with value is the series of nonwoven mats called "Saranlock" currently sold by the Japanese chemical company Asahi Kasei. As indicated in U.S. Patent No. 4,165,281 (Niigata Engineering Co., Ltd.), Saranlock mats can be used as biomass support material in wastewater treatment systems. Saranlock mats are currently supplied for a wide range of applications, including biomass support material. This is also stated on Asahi Kasei's website (https: / / www.asahi-kasei.co.jp / sarannet / en / saranlock.html). According to the site, Saranlock mats are available in thicknesses from 10mm to 50mm, F vThe value ranges from 0.03 to 0.07. Saranlock (trademark) is composed of adhesively bonded, curled short fibers of a thermoplastic copolymer in which the main monomer is vinylidene chloride (VDC) and the auxiliary monomer is vinyl chloride (VC). This copolymer is a type of polyvinylidene chloride copolymer family called PVDC fiber or Saran (registered trademark). The Saran (registered trademark) short fibers used in the manufacture of Saranlock (trademark) have an average straight (uncurled) length of approximately 150 mm. Based on the manufacturing method, Saranlock (trademark) can be described as an airlaid adhesive nonwoven mat.

[0007] One example of the use of nonwoven fabric mats is forming the base material for biomass support plates in rotating biological contactors (RBCs). RBCs are devices used in wastewater treatment (e.g., Japanese Patent No. 2007-301511, Japanese Utility Model No. H1-13600, Japanese Utility Model No. H1-16559, Japanese Utility Model No. H1-23594, Japanese Utility Model No. 3064723, Korean Patent No. 10-1019069).

[0008] As described in U.S. Patent No. 1811181, the RBC includes a horizontal rotor that rotates slowly within a tank. Within this tank, the wastewater to be treated flows horizontally due to gravity. The rotor includes a motor connected to a central shaft, to which several vertical plates are mounted at equal intervals. The wastewater flowing through the tank submerges approximately 35% to 40% of each rotating plate. Each part of each plate is alternately wetted by the wastewater and then exposed to air above the water surface. This alternating process promotes the growth of biomass on the plate surface, and the grown biomass removes contaminants from the wastewater.

[0009] The nonwoven RBC board described in the above Japanese and Korean literature is circular with an overall diameter of approximately 2 meters and contains six individual triangular sector-shaped plate sections. The mats constituting these plate sections are composed of curled fibers bonded together with adhesive at their intersecting surfaces. Typically, the polymer of choice is PVDC, with a fiber denier of 4000 and a mat denier of F v The value is approximately 0.04. This is consistent with the fact that the mat is manufactured from Saranlock®.

[0010] In conventional RBCs, the triangular plate sections are fixed around the rotor by 36 longitudinal tie rods. The tie rods are fixed to the rotor via circular steel plates and pass through six openings provided in each triangular plate section. Spacers are also positioned across the tie rods between adjacent plates to maintain uniform longitudinal spacing between them. The plate thickness is approximately 50 mm, and the pitch spacing is 100 mm.

[0011] Plates made from nonwoven mats offer significant advantages over conventional plates used in RBCs, which are made from rigid, hard thermoplastic sheets that are corrugated for increased flexibility. Compared to solid plates, nonwoven mat plates can maintain a much higher biomass concentration per unit volume of rotor (because biomass grows on the fiber surface and within the pores between the fibers). Therefore, RBC plates containing nonwoven mats are more effective in wastewater treatment per unit volume of plate.

[0012] However, the non-woven mat may lack sufficient rigidity in many of the applications to which it is applied. For example, the plates used in RBC units require a certain degree of rigidity to prevent lateral deflection when being washed away in the wastewater during treatment. None of the above Japanese patent documents teach a method of reinforcing the mat as a plate for RBC. These reinforcement methods improve the overall strength and fatigue resistance of the mat plate, and extend the operating life. For example, Japanese Utility Model No. H1-13600 and Japanese Utility Model No. H1-16559 teach attaching a mesh or a continuous plastic rigid sheet to the mat as a reinforcing upper structure. However, the manufacture of the upper structure attached to the non-woven mat is relatively expensive, and there is a risk that the upper structure may separate from the mat.

[0013] As another reinforcement method, there is a technique of providing flanges inherent in the non-woven mat. Generally, a flange refers to a protruding flat edge, collar, or rib on an object, and is intended for strengthening the object, attaching other objects, or holding a position. The flange portion incorporated in the non-woven mat can perform various functions as follows: · The flange portion improves the strength, rigidity, and dimensional stability of the entire mat. · The flange portion provided around the periphery or the opening of the non-woven mat enhances the erosion resistance of the edge. · The shaped flange portion can be used as a lug or other fixture for fixing the non-woven mat in the housing.

[0014] The flange portion may be incorporated as a rib penetrating the mat body (e.g., Korean Patent No. 10-1019069), or around the peripheral edge (e.g., in the form of forming a collar on the outer periphery or the edge of the opening of the mat). The flange portion is particularly effective in low-strength non-woven mats including those having a relatively low F v value.

[0015] A common method for forming flanges in Saranlock™ nonwoven mats is the use of thermal compression. Generally, this method involves heating the entire mat and then compressing the flange portion. This ensures that the fibers in that portion remain compressed even after cooling and decompression. Japanese Utility Model (Y) No. H1-23594 describes the use of this thermal compression method for forming flanges in Saranlock™ nonwoven mats around triangular plate sections and around fixed openings. Korean Patent No. 10-1019069, on the other hand, shows the formation of rib-like and periphery flanges through the body of the plate.

[0016] The compression method described above is effective for Saranlock-type mats because Saran® has the unique property of being highly crystalline compared to other thermoplastic materials. Therefore, heating the mat under compression destroys most of its crystallinity. Upon cooling, the Saran® fibers recrystallize, fixing the shape of the flange portion. Heating the Saran® fibers to a temperature at which their crystallinity is destroyed also removes the work hardening of the material, which may affect the tensile strength of the fibers. This flange portion formation method is not applicable to most (if not all) other thermoplastic materials.

[0017] The method for forming flanges in general-purpose thermoplastic fiber mats involves thermally compressing the flange portion at a temperature above the melting point of the thermoplastic material. Cooling causes the thermoplastic material to solidify, fixing the shape of the portion. However, the applicants have surprisingly discovered that this process can be problematic. This is because thermal compression of the flange portion can cause certain fibers connecting the compressed flange portion to the rest of the uncompressed mat to be excessively stretched. This process is problematic for relatively thick and F v Mats with a low value (for example, those with a thickness of 25mm or more and F v This is particularly noticeable in mats where the value is less than 0.1.

[0018] The inventors have demonstrated that this excessive elongation weakens or breaks the connecting fibers. Even if the integrity of the mat itself is not immediately impaired, the service life of the mat in the operating device is significantly shortened.

[0019] The weakening of the connecting fibers is a serious problem for the mat plates used in RBCs. In the treatment process associated with plate rotation in RBCs, wastewater flows into and out of the non-woven fabric plate. This bidirectional movement of the wastewater increases the magnitude of the force acting on the plate. Mainly two forces act on the non-woven fabric plate. The fluid shear stress of water acting on the surface and the gravitational force acting on the entire mass of the plate including the wastewater and the supported biomass. The non-woven fabric mat must withstand these repeated forces during the operating period, and the weakness at the joint between the plate flange part and the main body part reduces the life of the plate. When the plate deviates from the gripping position by the flange part around the fixing hole, the plate is damaged.

[0020] The Saran Lock (trademark) type mat is relatively expensive for two reasons. First, Saran (registered trademark), the raw material, is composed of 72% chlorine by mass, and chlorine is an expensive raw material, so Saran (registered trademark) itself is expensive. Second, the production of the mat supplied in a 2m×1m rectangular sheet is labor-intensive. Furthermore, the use of chlorinated polymers such as Saran (registered trademark), especially when these polymers are burned, is associated with environmental problems. There is a need for a cheaper and more robust alternative mat that can form a strong flange part within the structure. Summary of the Invention

[0021] Through extensive experiments, the inventors of the present invention have established a novel structure of a non-woven fabric mat and its manufacturing method that can provide a stronger flange part compared to mats that lose strength during thermocompression.

[0022] Accordingly, in a first embodiment of the present invention, a nonwoven mat formed from fibers comprising a first polymer material, wherein the mat includes a flange portion having a higher density than the rest of the mat, and the flange portion further comprises a second polymer material, the second polymer material being a thermoplastic resin having a lower melting point than the first polymer material.

[0023] The second polymer material may be provided in the entire mat or only in a part of the mat. For example, the fibers forming the mat or part of the mat may be two-component fibers containing both the first polymer material and the second polymer material. The first polymer material may, for example, form the central thread within the fiber, and the second polymer material may form the outer sheath of the fibers forming the mat. Furthermore, or alternatively, the mat or only a part of the mat may be formed from two types of fibers: one containing the first polymer material and the other containing the second polymer material. The fibers of the first and second materials can intertwine to form a nonwoven mat. Alternatively, a nonwoven mat may be formed by bonding, as necessary, one sheet of mat containing the first polymer material and one sheet of mat formed from the second polymer material. This latter embodiment is undesirable, and therefore, it is preferable that the nonwoven mat of the present invention does not include a configuration in which one sheet containing the first polymer material and one sheet containing the second polymer material are bonded together as necessary.

[0024] Since the second polymer material performs its function in the flange portion, it may not be substantially present in the rest of the mat. For example, the portion formed from the second polymer may be less than 10%, 8%, 6%, 4%, 2%, or 1% of the volume of the rest of the mat, and the rest may not be formed from the second polymer at all. In this embodiment, the rest is substantially composed of the first polymer material. For example, more than 90%, 92%, 94%, 96%, 98%, or 99% of the rest is formed from the first polymer material. The entire rest may be formed from the first polymer material.

[0025] The density of the flange portion is higher than that of the rest of the material. This is because the voids in the flange portion are fewer than those in the rest of the material. This can be achieved by the flange portion containing or comprising a matrix in which the fibers of the first polymer material are trapped (or entrapped) and fixed.

[0026] The flange portion is F v The value may be greater than 0.85, and arbitrarily greater than 0.9, greater than 0.95, or greater than 0.99. The flange portion has no voids at all, or substantially no voids.

[0027] The flange portion has a matrix containing or consisting of a second polymer material, in which fibers of the first polymer material may be dispersed. The dispersion of the fibers of the first polymer material within the second polymer material may be uniform or random.

[0028] The polymer material may be natural or synthetic, and may be a plastic polymer material. The second polymer material is thermoplastic, and the first polymer material may also be thermoplastic, provided that its melting point is higher than that of the second polymer material. As those skilled in the art will recognize, the melting point of a polymer material refers to the temperature range at which the material transitions from a solid state to an amorphous liquid with a change in viscosity. During the melting process, the polymer material absorbs latent heat. Determining the melting point of any polymer is within the usual range of art for those skilled in the art (e.g., by differential scanning calorimetry; examples are described in ISO 11357-3:2018, which are incorporated herein by reference). The melting point of the first polymer material may be 1°C, 2°C, 3°C, 4°C, 5°C, 10°C, 15°C, 20°C, 30°C, 40°C or more higher than the melting point of the second polymer material, and may optionally be less than 50°C, 45°C, 40°C.

[0029] Some thermoplastic polymer materials begin to decompose at temperatures below their melting point. Saran® is an example of such a polymer material. Decomposition of polymer materials is manifested by effects such as oxidation, chemical leaching, and chain and side group severance, which can reduce strength, fatigue resistance, and durability. To optimize the mat, it is preferable not to use such pyrolytic polymer materials as the second polymer material of the present invention. For example, the first and / or second polymer materials do not have to be PVDC. However, it is possible to use such materials as the first polymer material, provided that the temperature is maintained below the decomposition initiation temperature of the first polymer material during mat formation. In the case of Saran®, this temperature needs to be below 140°C.

[0030] As a pure example, if the first polymer material is high-melting-point polyethylene (HMPPE), the second polymer material may be low-melting-point polyethylene (LMPPE). The second polymer is preferably one that does not soften in water; that is, its strength and / or stiffness do not change, or are substantially unchanged, when immersed in water. If the first polymer material is polypropylene (PP), the second polymer material can be LMPPE, HMPPE, or a combination thereof. If the first polymer material is polyoxymethylene (POM), the second polymer material may be LMPPE, HMPPE, or a combination thereof. If the first polymer material is TPE, the second polymer material may be LMPPE, HMPPE, PP, POM, or a combination thereof. If the first polymer material is TPE, the second polymer material may be LMPPE, HMPPE, or a combination thereof. If the first polymer material is TPE, the second polymer material may be any of the LMPPE materials. If the first polymer material is polybutylene terephthalate (PBT), the second polymer material may be LMPPE, HMPPE, PP, POM, or a combination thereof. If the first polymer material is a polyamide (PA) such as nylon 66, the second polymer material may be LMPPE, HMPPE, PP, POM, PBT, or a combination thereof. The first polymer may be a thermoplastic copolyester elastomer, and the second polymer may be Lumicene® Supertough 22ST05 (manufactured by TOTAL Refining and Chemicals).

[0031] The polymer selected as the first or second polymer material may be a homopolymer. Optionally, the polymer may be a copolymer.

[0032] Under normal operating conditions, PP can become relatively brittle. However, when using PP as the primary polymer material for forming mesh fibers, brittleness can be reduced by forming the fibers from a PP / PE polymer blend. Therefore, if the primary polymer material is PP, it is effective to provide it as a blend of PP and PE. For example, PP can be 50-95% by weight and PE 50-5% by weight. Optimally, a polymer blend with a higher proportion of PP than PE is used.

[0033] When PP is selected as the polymer, especially when used as the primary polymer material, a nucleating agent may be included in the PP. This has been shown to improve the material's toughness.

[0034] In this specification, high-melting-point polyethylene (HMPPE) refers to polyethylene whose melting point is in the range of 120°C to 140°C, as determined in accordance with ISO 11357-3:2018.

[0035] In this specification, low-melting-point polyethylene (LMPPE) refers to polyethylene whose melting point is in the range of 100°C to 120°C, as determined in accordance with ISO 11357-3:2018.

[0036] In this specification, high-density polyethylene (HDPE) refers to polyethylene with a density of 940 kg / m³ as determined according to ISO 3507:1999. 3 From 970 kg / m 3 This refers to polyethylene within that range.

[0037] In this specification, low-density polyethylene (LDPE) refers to polyethylene with a density of 915 kg / m³ as determined according to ISO 3507:1999. 3 From 940 kg / m 3 This refers to polyethylene within that range.

[0038] As is clear, polyethylene can meet both the melting point definition and the density definition. For example, polyethylene can be HMPPE and HDPE, HMPPE and LDPE, LMPPE and HDPE, or LMPPE and LDPE. More commonly, HDPE is also HMPPE, and LDPE is also LMPPE.

[0039] In this specification, thermoplastic polyester elastomer (TPE) refers to a polymer that possesses both thermoplastic and elastomer properties. Thermoplastic polymers are polymers that can be easily melted and molded. They melt with heat and harden when cooled. Typical examples include nylon, polyester, and polyolefin. These materials do not contain crosslinking networks. Elastomers are natural or synthetic polymers that possess elastic properties. They elastically deform under tensile and compressive stresses, but then return to their original pre-deformation shape. Typical elastomers are natural rubber and silicone rubber. TPEs combine the properties of both thermoplastics and elastomers: they can be processed like plastics, but share the performance characteristics of rubber.

[0040] The flange portion may be thinner than the rest of the mat. This is due to the compression process used in the manufacturing of the flange portion. However, if a relatively large amount of the secondary polymer material is used, excess secondary polymer material may remain on the surface of the nonwoven mat even after compression. Therefore, the flange portion may form a raised surface that extends (or protrudes) from the surface of the nonwoven mat.

[0041] The nonwoven mat may be any known nonwoven mat, for example, a spun in-line nonwoven mat or a melt-bonded nonwoven mat. The fibers of such a mat containing the first polymer may have an average diameter greater than 0.3 mm. The fibers containing the first polymer may have an average length greater than 500 mm. The Fv value of the rest of the mat may be greater than 0.04, greater than 0.06, or greater than 0.08, for example, in the range of 0.04 to 0.1. The Fv value of the rest may be 0.85 or less, 0.7 or less, 0.5 or less, 0.3 or less, or 0.1 or less. Preferably, the Fv value of the rest is between 0.04 and 0.85, more preferably between 0.04 and 0.1. The thickness of the rest of the mat may be 15, 20, or 25 mm or more. Preferably, the thickness of the rest of the mat is 25 mm or more. The thickness of the remaining portion of the mat is preferably substantially uniform, such that it does not vary by more than 1, 5, or 10%.

[0042] The flange portion may be provided on the periphery of the mat. The flange portion may be provided on the periphery of the opening of the mat. The flange portion may be provided as a rib that penetrates the main body of the mat. The flange portion may be provided in a combination of the above.

[0043] The flange portion may serve as a mounting portion for fixing.

[0044] The method for forming the flange portion of the mat according to the present invention is important for achieving the robust structure identified by the inventors.

[0045] Therefore, in a further aspect of the present invention, a method for forming flanges on a nonwoven mat is provided. This method includes the following steps: Step a. To provide a nonwoven mat formed from fibers containing a first polymer material and a second polymer material. Step b. Heating the first and second polymer materials to a process temperature higher than the melting point of the second polymer material and lower than the melting point of the first polymer material, and Step c. Compress a portion of the nonwoven mat so that the compressed portion forms a flange portion.

[0046] The second polymer material may be provided throughout the entire mat. For example, the fibers forming the nonwoven mat may be two-component fibers containing both the first and second polymer materials. The first polymer material may, for example, form the central thread within the fiber, and the second polymer material may form the outer sheath of the fibers forming the mat. Furthermore, or alternatively, the mat may be formed from two types of fibers, one containing the first polymer material and the other containing the second polymer material. Furthermore, or alternatively, the second polymer material may be provided over the entire surface of the nonwoven mat or substantially over it. Because the second polymer material plays its role in forming the flange portion, the remaining portion of the mat that does not form the flange portion may not substantially contain the second polymer material. For example, less than 10%, 8%, 6%, 4%, 2%, or 1% of the volume of the remaining portion of the mat may be formed from the second polymer, or the remaining portion may not be formed from the second polymer at all. In this embodiment, the remaining portion may be substantially composed of the first polymer material. For example, more than 90, 92, 94, 96, 98, or 99% of the remaining portion may be formed from the first polymer material. The entire remaining portion may also be formed from the first polymer material.

[0047] Therefore, prior to step a, the process may include providing a nonwoven mat and applying (or coating) a second polymer material to its surface. The second polymer material may be applied only to the surface of the portion of the nonwoven mat to be compressed.

[0048] The second polymer material may be applied to the surface of the mat as a pre-formed sheet (e.g., cut from a plastic sheet or pre-formed). The second polymer material may be applied to the surface of the mat as granules, in which case the granules may fall into the interior of the mat. The second polymer material may be applied to the flange portion of the mat as a molten material (e.g., from a heated ejector). The second polymer material may be applied in any of the above application methods or a combination thereof.

[0049] Optionally, the minimum amount of the second polymer material applied to the flange portion of the mat is sufficient to fill any gaps in the compressed mat after compression, thereby maximizing the strength of the flange portion. In practice, tiny voids may remain in the flange portion after the thermal compression process is complete, but the F of the flange portion completed by this process v The value should be guaranteed to be 0.85 or higher. While the selected compression pressure is not strictly defined, it must be sufficient to avoid damaging the fibers of the first polymer material in the flange portion and to allow the second polymer material to substantially fill the volumetric voids in the compressed mat of the flange portion. Generally, the compression pressure is around 0.5 MPa to 2 MPa and may be indirectly related to the selected process temperature.

[0050] However, the amount of the second polymer material may exceed the minimum amount required to fill the void in the flange portion. This methodology can be used, for example, to manufacture flange portions that protrude from the surface of a compression mat for use as fixing lugs.

[0051] The heating step b and the compression step c can be performed simultaneously. The heating step b may precede the compression step c, provided that the time difference is not so long that the second polymer material cools down to the point where it can no longer maintain its molten state.

[0052] Heating step b may be achieved by applying heat to the compression mold located next to the flange, for example, using an electric heater or heating oil flowing through a conduit in the mold. The process temperature may be controlled by controlling the mold temperature to the process temperature or an equivalent temperature. The mold may be configured to surround the portion, and heating step b can be applied to the opposing surface of the nonwoven mat. Double-sided heating has the advantage of maximizing mold productivity.

[0053] Heating step b is applicable to only one side of the nonwoven mat. In the case of single-sided heating, it is preferable to heat the second polymer material indirectly through the compressed mat rather than directly from the opposite side. Such single-sided indirect heating prevents the molten second polymer material from flowing laterally outside the flange boundary. This heating method is ideal when forming a flange that protrudes from the mat surface.

[0054] The process temperature (or processing temperature, process temperature) refers to the temperature of the polymer material in the flange portion during the thermal compression process. This process is optimally operated at a temperature that does not cause permanent damage to the strength, fatigue resistance, or durability of the first or second polymer material.

[0055] The compression pressure used in process c is applied to the compression surface of the mold, compressing and solidifying the mat between both sides. It is desirable to apply the maximum pressure in a controlled manner after the mat temperature has reached the process temperature.

[0056] For specific first and second polymer materials, the selected thermal compression process temperature is within a range between a lower and upper limit. The lower limit of the process temperature must be high enough to liquefy the second polymer material, allowing the liquid to fuse with the compression mat during the thermal compression process. On the other hand, the upper limit of the process temperature must be set low enough to prevent the mat's fibers from stretching and suffering permanent damage during the thermal compression process. In the absence of relevant experimental data from test work, a good guideline is to assume that the upper limit of the process temperature is equal to the Vicat softening temperature (ISO 306:2013) of the first polymer material.

[0057] For example, the lower limit of the process temperature can be 0°C, 5°C, 10°C, 15°C, or 20°C higher than the melting point of the second polymer material, and can be at least 0°C, 5°C, 10°C, 15°C, or 20°C higher. The upper limit of the process temperature can be at least 5°C, 10°C, 15°C, or 20°C lower than the melting point of the first polymer material.

[0058] If the lower limit of the process temperature exceeds the upper limit of the process temperature, the flange portion according to the invention described herein cannot be manufactured using the two polymer materials.

[0059] Because the flange is compressed by a thermal compression process, the liquefied second polymer material flows only a short distance into the flange. Therefore, the process temperature during flange manufacturing can be set lower than that used in conventional thermal compression molding. By selecting a relatively high process temperature between the lower and upper limits of the applicable range, the pressure required to push the second polymer material into the flange during the thermal compression process can be reduced.

[0060] In one embodiment of this method, if the first polymer material is HMPPE, the second polymer material is LMPPE.

[0061] In one embodiment of this method, if the first polymer material is PP, the second polymer material may be LMPPE, HMPPE, or a combination thereof.

[0062] In one embodiment of this method, if the first polymer material is POM, the second polymer material may be LMPPE, HMPPE, or a combination thereof.

[0063] In one embodiment of this method, if the first polymer material is TPE, the second polymer material may be LMPPE, HMPPE, PP, POM, or a combination thereof.

[0064] In one embodiment of this method, if the first polymer material is PBT, the second polymer material may be LMPPE, HMPPE, PP, POM, TPE, or a combination thereof.

[0065] In one embodiment of this method, if the first polymer material is PA, the second polymer material may be LMPPE, HMPPE, PP, POM, TPE, PBT, or a combination thereof.

[0066] In one embodiment of this method, the nonwoven mat is spun in-line and melt-bonded.

[0067] In one embodiment of this method, the average diameter of the fibers containing the first polymer exceeds 0.3 mm.

[0068] In one embodiment of this method, the average length of the fibers containing the first polymer exceeds 500 mm.

[0069] In one embodiment of this method, the volume solid fraction of the uncompressible portion of the mat is greater than 0.04 and / or less than 0.85.

[0070] In one embodiment of this method, the flange portion is formed on the peripheral edge of the mat.

[0071] In one embodiment of this method, the flange portion is formed on the peripheral edge of the opening of the mat.

[0072] In one embodiment of this method, the flange portion is formed as a rib that penetrates the mat body.

[0073] In one embodiment of this method, the flange portion is a fixing mounting portion (or fixing fitment).

[0074] The features of the first aspect of the present invention are similarly applicable to the second aspect. For example, the combination of the first and second polymer materials used in this method is the same as that incorporated into the nonwoven mat described above, and the same fiber diameter and fiber length as the nonwoven mat may be used in this method.

[0075] The method of this aspect of the present invention may be used to manufacture any of the nonwoven mats of the first aspect of the present invention.

[0076] In a further aspect of the present invention, a nonwoven mat manufactured according to a second aspect of the present invention is provided.

[0077] In yet another aspect of the present invention, a nonwoven mat manufactured according to a prior aspect of the present invention is provided for use as a plate in a rotating disc contact device.

[0078] In yet another aspect of the present invention, a nonwoven mat manufactured according to a prior aspect of the present invention is provided for use in a filter, demister or floating treatment wetland. [Brief explanation of the drawing]

[0079] The present invention will be described with reference to the following drawings for illustrative purposes only. [Figure 1]Figure 1 shows examples of combinations of the first and second polymer materials. Some of these combinations can be used in the inventions described herein. In the typical melting point temperature range of polyethylene (PE) materials, LMPPE refers to low-melting-point polyethylene, and HMPPE refers to high-melting-point polyethylene. PP represents polypropylene, POM represents polyoxymethylene, TPE represents thermoplastic polyester elastomer, PBT represents polybutylene terephthalate, and PA represents polyamide (nylon 66). [Figure 2]Figure 2 compares the melting points of polymer materials in the exemplary combinations shown in Figure 1. In the exemplary combinations, both the first and second polymer materials are thermoplastic resins, and neither material undergoes thermal decomposition below its respective melting point. Each polymer material exhibits a melting point range related to differences in the polymer structure of the individual versions of the material that are manufactured. The temperature ranges shown in Figure 2 are typical for specific materials but do not necessarily cover the entire range. Examining the chart in Figure 2 reveals clear differences in melting point ranges in the following combinations: PA-PBT, PBT-POM, TPE-PP, PP-HMPPE, and HMPPE-LMPPE. In these combinations, there is a wide range of individual versions of the first and second polymer materials that are manufactured. In contrast, the melting point range for the POM-PP combination is continuous. Therefore, in this particular combination, the availability of individual versions of the first and second polymer materials is limited. The PP version should be selected from near the lower end of its melting point range, and the POM version from near the upper end of its melting point range. The most cost-effective polymer material is generally polyethylene. LMPPE has been found to roughly coincide with the established low-density polyethylene (LDPE) category, but not always. Similarly, HMPPE generally coincides with the established high-density polyethylene (HDPE) category. The density ranges of LDPE and HDPE are approximately 915-930 kg / m³ and 940-970 kg / m³, respectively. In the example of a spun inline mat with flanges, the melting point difference in the HMPPE-LMPPE combination is 19°C. The PBT and POM combination has the largest melting point difference between the first and second polymer materials, while the POM and PP combination has the smallest. [Figure 3]Figure 3 shows the structure of an open-type heat compression molding machine (5 and 6) for forming a flange portion on a nonwoven mat (7). In this case, the flange portion is formed using a flange-shaped body (8) molded from a second polymer material. Heat sources (9) are positioned on both sides of the molding machine to concentrate heat on the flange-shaped body. Alternatively, the flange shape can be heated from only one side. By closing the mold, the second polymer material is pushed from the flange shape into the interfiber spaces of the compressed mat. [Figure 4] Figure 4 shows a nonwoven mat (7) in an enclosed mold with a completed flange. The flange (3) on the outer periphery of the mat contains mat fibers trapped in a matrix of a second polymer material. In this case, the surface of the flange is coplanar with the surface of the compressed mat. [Figure 5] Figure 5 shows an elevation view of a plate section used in the aforementioned RBC unit (1) (e.g., U.S. Patent No. 4,165,281 (Niigata Engineering Co., Ltd.)). Each plate section is provided with six mounting openings (2). Flanges are shown around the plate section (3) and around the openings (4). [Figure 6] Figure 6 compares the Young's modulus values ​​of a new mat and an existing mat before and after long-term use in the RBC. The objective was to establish the mechanical stability of the mat under long-term use, which is subject to typical mechanical stress and frequent submersion. [Figure 7] Figure 7 shows the test results of measuring the tensile strength (UTS) of the existing and new mats before and after use in a rotating disc contact device (RBC). The purpose was to confirm that the new mats, when molded into plate sections (see Figure 5), had sufficient tensile strength for use in the RBC and remained stable for several months. [Figure 8] Figure 8 shows the locations (TL1-TL6) of the stiffness tests performed on the periphery flanges of existing and new plate sections. The objective is to establish the stiffness of the manufactured plate section (including the mat reinforced with molded flanges). [Figure 9]Figure 9 compares the load-bearing deflection of existing and new plate sections at two test locations (TL1 and TL4). [Figure 10] Figure 10 compares the stiffness parameter values ​​at all test locations. The results show that the new plate section exhibits less deflection under load and is significantly stiffer than the existing plate section. [Modes for carrying out the invention]

[0080] Nonwoven mats are used in a wide range of products, including cushioning, clothing, hygiene products, geotextile membranes, paper and cardboard, insulation materials, and various filters. Producing such a diverse range of products requires nonwoven mats with a variety of properties and structures, determined by variables such as the physical properties of the fibers and polymer materials, fiber arrangement methods, inter-fiber bonding, finishing methods, and mat thickness.

[0081] For example, the improved flange formation method is applied to spun inline melt-bonded mats manufactured using a method similar to that described on Asahi Kasei's website. In this example, the mat is extruded from a die with multiple holes, using a molten first polymer material as the direct raw material. The hole diameter is 0.7 mm, and the hole pitch is 5 mm. The working surface of the die is 80 mm wide x 2 m long and has 5600 extrusion holes. Numerous fibers fall vertically by gravity in a molten state and are wound up spirally on a water-cooled roller. This causes the fibers to be arranged spirally on the water surface, and adjacent surfaces fuse together. The bonded mat falls into cooling water and is transferred onto an underwater conveyor. This inline continuous process allows for the very cost-effective production of long mats. Using the improved method described here, a second polymer material is used to form flanges on the above mat.

[0082] Consider a mat including a flange portion. The fibers have a structure comprising a first polymer material, and the flange portion comprises compressed fibers embedded in a matrix of a second polymer material, which is a thermoplastic resin. The method for manufacturing the flange portion described herein is applicable to any first polymer material, provided that it is not significantly affected physically and chemically by the conditions of the thermal compression process used in manufacturing the flange portion.

[0083] The thermal compression method described here involves applying a process compression pressure at the process temperature to a heated flange portion.

[0084] Figure 3 is an exploded view partially showing the two-part components (5) and (6) of the heat compression mold for manufacturing the flange. The mat (7), the second polymer material (8), and the two heating elements (9) are also shown. Figure 4 is a partially shown fully sealed mold containing the flange (3).

[0085] Figure 4 shows the case where the second polymer material is applied to the flange portion as a pre-formed shape (8). This shape is cut from a plastic sheet having a predetermined polymer material and thickness, or pre-formed from the material. The pre-formed shape is made to have the same planar width as the flange portion. The pre-formed flange shape is applied to the surface of the flange portion and is preferably bonded to the mat surface using a hot melt adhesive to hold it in place.

[0086] The second polymer material can also be applied to the flange portion in the form of granules uniformly scattered on the mat surface. Particles smaller than the pore size of the mat may fall into the flange portion, but this does not impair the manufacturing or strength of the finished flange portion.

[0087] Furthermore, the second polymer material is applied to the flange portion of the mat as a hot melt via a lance, preferably via a robot-driven lance.

[0088] The molds shown in Figures 3 and 4 are heated from both sides to maximize productivity. The temperature of the heating element (9) is precisely controlled to melt the second polymer material while restoring its initial strength after cooling without damaging the fibers. The conditions and duration of thermal compression are controlled to achieve the desired effect on the flange portion while maximizing productivity.

[0089] When using single-sided heating, it is preferable to apply the heating to the compression mat side that is not in contact with the second polymer material. This allows the second polymer material to be heated through the compression mat. This type of heating is referred to herein as "indirect heating." Such indirect heating improves the flow of the molten second polymer material into the compression mat and minimizes lateral flow into the open mat outside the flange portion.

[0090] The application of process compression pressure to the flange portion should preferably be delayed until the temperature of the second polymer material reaches the process temperature.

[0091] The second polymer material substantially fills the spaces between the fibers of the first polymer material in the flange portion, thereby maximizing the strength and stiffness of that portion. v The value exceeds 0.85. According to empirical rules, the minimum thickness Tm (mm) of the pre-formed flange shape required to fill the space is equal to the initial volume solid fraction F of the mat. v And the thickness T (mm) is related as follows: Tm≒TF v (Formula 2)

[0092] Similarly, the thickness Tf of this flange portion is given by the following equation: Tf ≈ 2TF v (Formula 3)

[0093] Let's consider a mat with a volume solid fraction Fv of 0.06 and a thickness T of 50 mm as an example. According to Equation 2, Tm is approximately 3 mm. Therefore, in this case, a flange shape of this thickness can be cut from a standard plastic sheet. According to Equation 3, Tf is approximately 6 mm.

[0094] The flange portion protruding from the surface of the compression mat may be created using a pre-formed flange shape with increased thickness. To obtain the required thickness of the pre-formed shape, the required height of the flange portion protrusion is added to the thickness Tm. Since the protruding flange portion is heated indirectly through the compression mat, the protruding portion of the pre-formed flange shape is not affected by thermal compression.

[0095] Characterization of the test mat As an example, the present invention is applied to the manufacture of RBC plate sections of the shape and dimensions shown in Figure 5. These plate sections and mat samples cut from the plate sections were tested, and the results are discussed below with reference to Figures 6 and 7. The first and second polymer materials consist of thermoplastic polyester elastomer (TPE) and low-melting-point polyethylene (LMPPE), respectively. Based on density, both polymers are classified into the TPE and LDPE categories. Specifically, they are TPC-ET (thermoplastic copolyester elastomer) and MDPE Lumicene® Supertough 22ST05.

[0096] The mats in the plate section were spun inline using molten TPE in a manner similar to that described on Asahi Kasei's website. The mat thickness was 50 mm, F v The value is 0.057. The fibers are continuous, with an average diameter of 0.75 mm. The flange section is 5.7 mm thick and was manufactured using a pre-formed shape with a thickness of 3 mm.

[0097] The process temperature and compression pressure used to fabricate the flange section were 125°C and 1.2 MPa, respectively. For comparison, the melting points of TPE and LDPE were 205°C and 113°C, respectively, and their densities were 1190 kg / m³. 3 and 921 kg / m 3 The softening temperature of TPE Vicat A50 is 180°C.

[0098] Testing of mat and plate sections The RBC plate sections manufactured by the method described herein are compared with commercially available plate sections manufactured by the methods described in Japanese Patent Application No. 2007-301511(A) and Korean Patent No. 10-1019069 in terms of strength and flexibility. Both types of plate sections have substantially the dimensions and shape shown in Figure 5.

[0099] Purchased plate sections are referred to herein as “existing plate sections.” Plate sections manufactured using the present invention and subject to testing as described herein are as described in the “Characterization of Test Mats” above and are referred to as “new plate sections.” Similarly, the mats used in the manufacture of the plate sections are referred to as “existing mats” (i.e., purchased items) and “new mats” (i.e., as described in the “Characterization of Test Mats” above).

[0100] Figure 5 shows a plate section (1), six fixing openings (2), peripheral flanges around the fixing openings (4), and peripheral flanges around the plate section (3). The flange thicknesses differ between the two types of plate sections. The flange thickness of the existing plate section is approximately 4 mm, while the flange thickness of the new plate section is 5.7 mm. This thickness was obtained using the minimum thickness Tm of the second polymer material.

[0101] The new mat is a spin-in-line melt-bonded type, while the existing mat is an airlaid adhesive-bonded type. The appendix table lists the main characteristics of the major nonwoven mats. The existing mats are the types shown in the second column from the left in the table, and the new mats are the types shown in the rightmost column of the table.

[0102] Table 1 compares the physical and chemical properties of the existing and new plate sections. Compared to the existing mat, the new mat is F v Although the values ​​are high (0.057 vs. 0.04), the overall density is low (53 kg / m³) due to the low fiber density of the first polymer material.3 Ratio 68 kg / m 3 ).

[0103] [Table 1]

[0104] To establish the mechanical properties of the mat and to verify the reinforcing effect of the flange portion when the mat is formed into a plate section, tests were conducted on new and existing mat sections and plate sections.

[0105] The Young's modulus (YM) and ultimate tensile strength (UTS) were measured for existing and new mat samples. YM is an indicator of dimensional stability; a higher value indicates better dimensional stability, while a lower value indicates higher elasticity. UTS is an indicator of the material's resistance to fracture under tension; a higher value indicates higher material strength.

[0106] Mat samples were cut from manufactured plate sections. The tests were first performed on samples from unused plate sections, and then on plate sections that had been used in a rotating disc contact device for at least 30 weeks. The objective was to compare the YM and UTS values ​​of both mats and clarify the effects of long-term use.

[0107] Samples of plate sections manufactured using existing and new methods were tested, and their resistance to deflection under load was compared. Stiffness parameters were defined for comparison.

[0108] Comparison of mechanical strength and stability As shown in Table 2, six new plate sections and six existing plate sections were tested. The plate sections were installed in a fully operational RBC for 30 weeks.

[0109] The Young's modulus (YM) was measured before and after long-term use in a full-scale RBC using four samples taken from a new plate section and four samples taken from an existing plate section. Subsequently, tensile tests were performed to measure the ultimate tensile strength (UTS).

[0110] In these tests, rectangular specimens were cut from the plate section. Each specimen measured 100 mm wide by 300 mm long, with one 100 mm side forming part of the flange on the outer edge of the plate. The other 100 mm side was filled with epoxy resin to form a solid strip 25 mm wide and 50 mm thick. This allowed for secure fastening with test clamps without distorting the fibers.

[0111] The novel mat is formed by a process involving inline linear extrusion of spinning and melt bonding, resulting in different tensile properties in the longitudinal and width directions of the mat. Plate sections were cut using the method described above, and two samples with the mat oriented longitudinally and two samples with the mat oriented widthwise were analyzed separately. The existing mat is formed by a non-directional process (airlaid + adhesive bonding), and its tensile properties are similar in all directions.

[0112] [Table 2]

[0113] Figure 6 compares the Young's moduli, showing that the new plate section exhibits similar stiffness to the existing mat in the widthwise direction, but has a much lower Young's moduli (i.e., higher elasticity) in the lengthwise direction. This is because the fibers are curled while being arranged longitudinally during mat manufacturing. Importantly, Figure 6 shows that the Young's moduli of the new plate section remained almost unchanged during 30 weeks of use in RBC, while the Young's moduli of the existing plate section decreased over a longer period, indicating a decrease in material stiffness over time.

[0114] Figure 7 shows that the ultimate tensile strength of the new plate section is lower than that of the existing plate section. However, the strength of the new plate section remained almost constant even after long-term use, whereas the strength of the existing plate section decreased significantly after RBC use. Since the load applied during UTS measurement significantly exceeded the load expected within the RBC and when applying the same technology, both materials are judged to have sufficient tensile strength.

[0115] All samples of new and existing mats failed within the mat (at their respective final loads), rather than at the joint between the flange and the rest of the mat. This indicates that forming the flange using the invention described herein or the method described in Japanese Patent Application No. 2007-301511 produces a portion that is securely bonded to the mat.

[0116] Comparison of rigidity Another test group was conducted to compare the deflection and stiffness of new and existing plate sections under load. The tests were performed on the entire plate section.

[0117] The test apparatus includes a rigid frame with six bolt fixing points to securely hold individual plate sections horizontally. The six bolts, accompanied by washers with the same outer diameter (85 mm) as the flange portion around the holes, pass through the six fixing holes and secure the individual plate sections to the frame.

[0118] New and existing plate sections were immersed in water for 25 days to simulate the effects of short-term hydrolysis on the strength of the plate sections.

[0119] In the test, as shown in Figure 8, six test positions (TLs) were set at different locations around the outer flange. For example, TL4 is on the outer circumference of the outer flange, and TL1 is on the inner circumference opposite in diameter.

[0120] At each test location, an upward vertical load was applied via the chain and catch to test the rigidity of each section. As shown in Figure 8, the catch (10), made of a 3 mm diameter angled stainless steel rod, passes under the flange portion. Due to its design, the applied vertical load passes through the center of the flange portion. In all tests, the catch did not penetrate or damage the peripheral flange portion of new or existing plate sections.

[0121] Using a conventional tensile testing machine, the applied upward vertical load was increased from zero, and the test continued until the applied load reached 100N or the measured vertical deflection reached a maximum of 50mm. Such deflections are significant because the plate section is 50mm thick and would not occur in normal practical environments. The pressure range used in the test was wider than the range the plate section would experience under normal operating conditions in RBCs and similar devices.

[0122] In the test, the resistive mechanical stress on the flange portion and the adjacent mat acted in response to the applied vertical force.

[0123] The test results were compared in terms of deflection and stiffness, and the stiffness parameter S (N / mm) was derived using the following formula: S=F / D (formula 4) Here, F(N) is the applied force and D(mm) is the deflection. The stiffness value is based on whichever condition occurs first: a maximum deflection of 50 mm or a maximum force of 100 N.

[0124] Figure 9 shows the relationship between deflection and applied force at test positions TL1 and TL4 for the new and existing plate sections. Under a load of 20 N, the deflection at TL1 was approximately 50 mm for the existing plate section, but only 25 mm for the new plate section. Similarly, the deflections at TL4 were approximately 14 mm and 7 mm, respectively. Therefore, these results indicate that the new plate section exhibits significantly better resistance to deflection under load compared to the existing plate section.

[0125] High loads of 100N are not practical under normal operation within the RBC. However, under this high load, the deflections of the existing and new plate sections in TL4 were 48mm and 37mm, respectively, confirming that the new plate section exhibited lower deflection values ​​across a wider load range.

[0126] Figure 10 compares the stiffness parameter S (N / mm) values ​​calculated from Equation 4 at all test locations for new and existing plate sections. The results show that the new plate has higher stiffness than the existing plate at all locations. Furthermore, the stiffness parameter value was highest at TL4 and lowest at TL1. Referring to Figure 8, which shows the test locations and the positions of the fixed openings, this result suggests that the stiffness is inversely proportional to the distance between the test location and the fixed opening.

[0127] The new plate section possesses significantly higher rigidity to counteract deflection from the plate section. Conversely, it exhibits greater elasticity within the mat to accommodate slight movements within the mesh plane. These characteristics are advantageous in applications such as within RBCs. Importantly, the YM and UTS of the new mat remained constant even after long-term use within an RBC. This suggests that the mechanical properties of the plate section remain stable throughout its lifespan.

[0128] appendix The table below summarizes the main characteristics of various nonwoven mats.

[0129] [Table 3]

[0130] Note: *Mat joining methods include: A = Air Entallgent (related to air) C = pressure compression, G=adhesion; F = heat welding, H = Hydroentanglement (related to water flow) M = molten entanglement and welding. N = Needle punch, S stitch

Claims

1. A nonwoven mat formed from fibers containing a first polymer material, wherein the mat includes a flange portion that is denser than the rest of the mat, and the flange portion further contains a second polymer material. The second polymer material is a thermoplastic resin, which has a lower melting point than the first polymer material, and is a nonwoven mat.

2. The nonwoven mat according to claim 1, wherein the second polymer material is substantially absent in the rest of the mat.

3. The nonwoven mat according to claim 1 or 2, wherein the volume solid fraction of the flange portion exceeds 0.

85.

4. A nonwoven mat according to any one of the claims, wherein the melting point temperature of the first polymer material is 1°C, 2°C, 3°C, 4°C, 5°C, 10°C, 15°C, or 20°C, 30°C, or 40°C or more higher than the melting point temperature of the second polymer material.

5. A nonwoven mat according to any one of the claims, wherein the flange portion comprises a matrix containing a second polymer material in which fibers of a first polymer material are trapped.

6. The nonwoven mat according to any one of the claims, wherein the flange portion comprises a matrix comprising a second polymer material in which fibers of a first polymer material are uniformly dispersed and / or randomly dispersed.

7. The nonwoven mat according to any one of the claims, wherein the flange portion forms a raised surface extending from the surface of the mat.

8. If the first polymer material is HMPPE, then the second polymer material is LMPPE, or If the first polymer material is PP, the second polymer material may be LMPPE, HMPPE, or a combination thereof, or If the first polymer material is POM, the second polymer material may be LMPPE, HMPPE, or a combination thereof; or If the first polymer material is TPE, the second polymer material may be LMPPE, HMPPE, PP, POM, or a combination thereof; or If the first polymer material is PBT, the second polymer material may be LMPPE, HMPPE, PP, POM, TPE, or a combination thereof; or The nonwoven mat according to any one of the claims, wherein the first polymer material is PA, and the second polymer material may be LMPPE, HMPPE, PP, POM, TPE, PBT, or a combination thereof.

9. The nonwoven mat according to any one of the claims, wherein the nonwoven mat is spun in line and melt-bonded.

10. A nonwoven mat according to any one of the claims, wherein the fibers containing the first polymer have an average diameter greater than 0.3 mm, and / or the fibers containing the first polymer have an average length greater than 500 mm, and / or the volume solid fraction of the rest of the mat is greater than 0.04 and / or less than 0.

85.

11. The nonwoven mat according to any one of the claims, wherein the flange portion is located on the periphery of the mat and / or the flange portion surrounds the periphery of the opening of the mat.

12. The nonwoven mat according to any one of the claims, wherein the flange portion is a rib that penetrates the mat body.

13. A nonwoven fabric mat according to any one of the above claims, wherein the flange portion is a fixing mounting portion.

14. A nonwoven mat according to any one of the claims, used as a plate in a rotating disc contact device and / or in a filter, demister, or floating treatment wetland.

15. A method for forming a flange on a nonwoven mat, the method comprising the following steps: Step a. To provide a nonwoven mat formed from fibers containing a first polymer material and a second polymer material. Step b. Heating the first and second polymer materials to a process temperature higher than the melting point of the second polymer material and lower than the melting point of the first polymer material, and Step c. Compress a portion of the nonwoven mat so that the compressed portion forms a flange portion.

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