JP5422874B2 - Nonwoven fabric for filter and method for producing the same - Google Patents

Description

  The present invention relates to a non-woven fabric for a filter having excellent dust collection performance, low pressure loss, and excellent mechanical properties and rigidity, and a method for producing such a non-woven fabric.

  Conventionally, various nonwoven fabrics have been proposed as materials for air filters or liquid filters for removing dust. Particularly in recent years, thermocompression-type long fiber nonwoven fabrics having excellent rigidity have been suitably used as pleated filters. When a pleated filter material is used, it is possible to reduce the filtration wind speed because a large filtration area can be obtained, and there is an advantage that the dust collecting ability can be improved and the mechanical pressure loss can be reduced.

  However, the conventional thermocompression-bonded long-fiber nonwoven fabric has an excellent balance between dust collection performance and pressure loss, and does not have sufficient rigidity for pleating. In other words, in the conventional technology, the fiber diameter of the fibers constituting the nonwoven fabric is about 10 μm even if it is thin, and the design is intended to control the dust collection performance and pressure loss of the nonwoven fabric only by the degree of opening due to the fineness of this fiber. This is because it was thoughtful.

  For example, Patent Document 1 proposes a composite long-fiber nonwoven fabric for filters made of deformed fibers. According to this technology, it is said that the mechanical properties and dimensional stability of the nonwoven fabric for filters can be improved, but the fiber diameter of the fibers constituting the nonwoven fabric is 2 to 15 dtex, that is, about 13 μm even if thin. It is. In addition, this technique increases the surface area per unit weight of the fiber by increasing the shape of the fiber cross section, and increases the contact area with the dust to improve the collection performance. When deformed fibers are employed in melt spinning, generally, the degree of fiber deformity is not so high due to polymer flow during melt extrusion. For this reason, a significant increase in surface area cannot be expected, and dust having a particle size of several μm or less cannot be sufficiently collected.

  Further, Patent Document 2 proposes a filter nonwoven fabric in which a plurality of nonwoven fabrics are laminated. According to this technique, it is considered that a non-woven fabric for a filter having a high basis weight can be easily produced, and a non-woven fabric for a filter excellent in air permeability can be obtained. However, the nonwoven fabric proposed in this technology is a laminate of a nonwoven fabric having a fiber diameter of 7 to 20 μm and a nonwoven fabric having a fiber diameter of 20 to 50 μm. It was not enough to collect the dust. In addition, after a plurality of non-woven fabrics were once manufactured, lamination and integration processing had to be performed separately, and the productivity was not high.

  Patent Document 3 proposes a non-woven fabric for a filter formed by adhering a binder resin to a long-fiber non-woven fabric that has been partially heat-welded. According to this technique, it is considered that a non-woven fabric for a filter having excellent pleat processability and less fuzzing can be obtained, but the processing cost becomes very high because the binder resin application processing is required. Furthermore, since the binder resin fills the gaps between the constituent fibers, the dust collection performance is lowered and the pressure loss is increased.

Furthermore, Patent Document 4 proposes a non-woven fabric for a filter obtained by fusing the fibers in the surface layer portion of a long-fiber non-woven fabric that is partially heat-welded. According to the technology, it is said that a non-woven fabric for a filter with less fuzz generation can be obtained even by long-term use. Generally, when heat fusion of constituent fibers of the surface layer portion is promoted, the fusion portion is formed. When the surface area of the fiber increases and the surface area of the fiber decreases, the contact area with the dust decreases and the collection performance decreases. Furthermore, in the manufacturing process, the fibers of the surface layer part are fused with a flat roll after partial thermocompression treatment with an embossing roll. When the number of such fused fibers increases, the fiber surface area for collection is increased. The decrease in pressure and the increase in pressure loss are problems. Also, when the partial thermocompression treatment is performed first, the sheet is partially thermocompression bonded at one time, so that it is difficult to adhere unless it is at high temperature and high linear pressure. In such a case, the sheet is crushed and is a preferable form as a filter. No nonwoven fabric can be obtained. In addition, when the fibers are fused and the gap between the fibers is reduced, there is a problem that the pressure loss increases, and the collection performance and the pressure loss are not excellent.
JP 2001-276529 A JP 2004-124317 A JP 2005-111337 A JP 2005-7268 A

  In view of the above-described problems of the prior art, the present invention provides a nonwoven fabric for a filter that is excellent in the balance between dust collection performance and pressure loss, and that is excellent in mechanical strength and rigidity. Furthermore, the present invention provides a method for producing such a nonwoven fabric for filters.

  The present invention employs the following means in order to solve such problems.

That is,
(1) A fiber web composed of thermoplastic continuous filaments is subjected to pressure contact treatment with a flat roll under conditions of a surface temperature of (Tm-50) ° C. to (Tm-180) ° C., and then partially thermocompression bonded with a hot embossing roll. A non-woven fabric for a filter having a QF value (Pa ⁻¹ ) of 0.02 to 0.08 and a bending resistance of 2 to 80 mN.
Tm represents the melting point of the resin having the lowest melting point present on the fiber surface of the fiber web.

  (2) The nonwoven fabric for filters according to the above (1), further having a bending resistance of 2 to 25 mN.

  (3) The thermoplastic continuous filament is composed of a composite filament in which a polyester low-melting polymer is arranged around a polyester high-melting polymer, (1) or (2) The nonwoven fabric for filters as described.

  (4) The thermoplastic continuous filament is composed of a mixed filament of a filament composed of a polyester-based high melting point polymer and a filament composed of a polyester-based low melting point polymer (1) or (2) The nonwoven fabric for filters according to the description.

  (5) The filter nonwoven fabric according to any one of (1) to (4), wherein the pressure-bonding area ratio is partially thermocompression bonded at 5 to 30%.

  (6) The nonwoven fabric for a filter according to any one of (1) to (5), which is processed into a pleated shape.

(7) After the thermoplastic polymer is melt extruded from the spinneret, it is pulled and stretched by air soccer to form a thermoplastic continuous filament, which is charged and opened and deposited on the moving collection surface to form a fiber web. The fiber web is subjected to pressure contact treatment with a flat roll at a surface temperature of (Tm-50) ° C. to (Tm-180) ° C., and then subjected to partial thermocompression bonding with a hot embossing roll to form a long fiber nonwoven fabric. A method for producing a non-woven fabric for a filter, characterized by comprising:
Tm represents the melting point of the fiber web and the resin having the lowest melting point present on the fiber surface of the fiber web.

  (8) The method for producing a nonwoven fabric for a filter according to (7), wherein the thermoplastic continuous filament is a composite filament in which a polyester low-melting polymer is arranged around a polyester high-melting polymer.

  (9) The method for producing a nonwoven fabric for a filter according to (7), wherein the thermoplastic continuous filament is a filament made of a polyester-based high melting point polymer and a polyester-based low melting point polymer. .

  (10) The press-contact treatment with the flat roll is characterized in that the fibrous web is heated and pressed by a pair of flat rolls to form a nonwoven fabric, and the nonwoven fabric is continuously brought into contact with the flat roll from the heated press-contact portion. The manufacturing method of the nonwoven fabric for filters as described in any one of said (7)-(9).

  ADVANTAGE OF THE INVENTION According to this invention, the nonwoven fabric for filters excellent in the balance of dust collection performance and pressure loss, and excellent in mechanical strength and rigidity can be provided. Moreover, the manufacturing method of such a nonwoven fabric for filters can be provided.

  The nonwoven fabric for filters of the present invention is a nonwoven fabric in which thermoplastic continuous filaments are partially thermocompression bonded and integrated.

  Examples of the raw material resin for the thermoplastic continuous filament include polyester polymers, polyamide polymers, polyolefin polymers, and mixtures thereof. Most preferred is a polyester polymer having a high melting point and excellent heat resistance and rigidity. In addition, a crystal nucleating agent, a matting agent, a pigment, an antifungal agent, an antibacterial agent, a flame retardant, a hydrophilic agent, and the like may be added to the thermoplastic continuous filament as long as the effects of the present invention are not impaired.

  A nonwoven fabric is constituted by these thermoplastic continuous filaments, that is, the nonwoven fabric of the present invention is a long-fiber nonwoven fabric, but the thermoplastic continuous filaments may have appropriate cut portions.

  It is also a preferred embodiment that a polyester-based high melting point polymer and a polyester-based low melting point polymer are respectively melt spun to form a long fiber nonwoven fabric as a mixed fiber. Furthermore, it is the most preferable form to use a long-fiber nonwoven fabric as a composite filament in which a polyester low-melting polymer is arranged around a polyester high-melting polymer. Here, the content ratio of the polyester-based high melting point polymer and the polyester-based low melting point polymer is preferably in the range of 30:70 to 95: 5, more preferably in the range of 40:60 to 90:10. Further, the polyester-based high melting point polymer preferably includes polyethylene terephthalate, and more preferably includes polyethylene terephthalate as a main component. Here, the content as a main component is preferably 50% by weight or more, more preferably 70% by weight or more, and further preferably 90% by weight or more. The polyester-based low-melting point polymer preferably includes a copolymer polyester or polybutylene terephthalate, and more preferably includes a copolymer polyester or polybutylene terephthalate as a main component. Here, the content as a main component is preferably 50% by weight or more, more preferably 70% by weight or more, and further preferably 90% by weight or more. The most preferable polyester-based low-melting point polymer is one containing a copolyester as a main component. Further, isophthalic acid and adipic acid are particularly preferred as the copolymer component of the copolymer polyester.

  The difference in melting point between the polyester high-melting polymer and the polyester low-melting polymer is preferably 15 ° C. or higher, more preferably 20 ° C. or higher. The melting point of the polymer in the present invention is measured at a temperature rising rate of 20 ° C./min using a differential scanning calorimeter, and is a temperature giving an extreme value in the obtained melting endothermic curve. For a polymer whose melting endotherm curve does not exhibit an extreme value in a differential scanning calorimeter, the polymer is heated on a hot plate, and the temperature at which the resin is melted by microscopic observation is defined as the melting point.

  In the present invention, a composite filament in which a polyester-based low-melting polymer is arranged around a polyester-based high-melting polymer is composed of a high-melting polymer having a low-melting polymer completely covered around the high-melting polymer. A preferred form is one in which a low-melting point polymer is intermittently arranged around the coalescence.

  In the present invention, the single fiber fineness of the thermoplastic continuous filament constituting the nonwoven fabric is preferably in the range of 1 to 10 dtex. When the fineness of the thermoplastic continuous filament is less than 1 dtex, the pressure loss of the nonwoven fabric tends to be high, and it is not preferable from the viewpoint of production stability because yarn breakage tends to occur during production. Further, when the fineness of the thermoplastic continuous filament exceeds 10 dtex, the collection performance of the nonwoven fabric tends to be lowered, and it is also preferable from the viewpoint of production stability such that the filament is likely to break due to poor cooling of the filament during production. Absent. A more preferable range of single fiber fineness is a range of 1 to 8 dtex. In addition, the single fiber fineness here says the value calculated | required as follows. That is, 10 small sample samples are randomly collected from the nonwoven fabric, photographed 500 to 3000 times with a scanning electron microscope or the like, 10 fibers are selected from each sample, and a total of 100 fibers are arbitrarily selected. Measure the thickness. The fiber is assumed to have a circular cross section, and the thickness is the fiber diameter. The fineness is calculated from the fiber diameter calculated by rounding off the first decimal place of the average value and the density of the polymer, and the first decimal place is rounded off. Moreover, when multiple types of fiber are mixed, the single fiber fineness of each fiber should just be in the said range.

  Furthermore, the cross-sectional shape of the thermoplastic continuous filament is not limited at all, but it may be circular, hollow round, elliptical, flat, or deformed, such as X or Y, polygonal, multileaf, etc. This is a preferred form. When adopting cross-sectional shapes such as X-type, Y-type, etc., polygonal, multi-leaf type, etc. in a composite filament in which a polyester-based low-melting polymer is arranged around a polyester-based high-melting polymer, In order to facilitate thermocompression bonding, the polyester-based low melting point polymer component is preferably present in the vicinity of the outer peripheral portion of the fiber cross section so that it can contribute to thermocompression bonding.

The nonwoven fabric for filters of the present invention has a QF value (Pa ⁻¹ ) in the range of 0.02 to 0.08. When the QF value (Pa ⁻¹ ) is less than 0.02, the collection performance and pressure loss are not sufficient, which is not preferable. Moreover, in the nonwoven fabric for filters, it is difficult to obtain a QF value (Pa ⁻¹ ) exceeding 0.08 in consideration of the basis weight and integration method of the nonwoven fabric. A more preferable QF value (Pa ⁻¹ ) is 0.03 to 0.08. In addition, the QF value in the present invention is calculated by the following formula, and is rounded off to two decimal places.
QF value (Pa ⁻¹ ) = − [ln (1- [collecting performance (%)] / 100)] / [pressure loss (Pa)]
The collection performance and pressure loss in the above equation are measured by the following measuring method or a measuring method that can obtain a result equivalent to this. That is, three samples of 15 cm × 15 cm are collected from an arbitrary portion of the nonwoven fabric, and the collection performance and pressure loss are measured for each sample with the collection performance measuring device shown in FIG. This collection performance measuring apparatus has a configuration in which a dust storage box 2 is connected to the upstream side of a sample holder 1 for setting a measurement sample M, and a flow meter 3, a flow rate adjusting valve 4 and a blower 5 are connected to the downstream side. Yes. Further, the particle counter 6 is connected to the sample holder 1, and the number of dusts on the upstream side and the number of dusts on the downstream side of the measurement sample M can be measured via the switching cock 7. In the measurement of the collection efficiency, a solution containing polystyrene particles (for example, Nacalai Tech 0.309 U polystyrene 10 wt% solution) is diluted with distilled water (for example, Nacalai Tech 0.309 U is diluted up to 200 times). Fill the dust storage box 2. Next, the sample M is set in the holder 1, and the air volume is adjusted by the flow rate adjusting valve 4 so that the filter passing speed is 3.0 m / min, and the dust concentration is 20,000 to 70,000 pieces / (2.83 × 10 ^-4 m ³ (0.01 ft ³ )), the dust number D2 upstream of the sample M and the dust number D1 downstream are set to a particle size of 0 with a particle counter 6 (for example, KC-01D manufactured by Rion). Each value is measured in the range of 3 to 0.5 μm, and the value obtained by rounding off the first decimal place of the numerical value obtained by the following formula is the collection performance (%).

Collection performance (%) = [1- (D1 / D2)] × 100
Here, D1: downstream dust count (total of 3 times)
D2: Number of upstream dust (total of 3 times)
The pressure loss (Pa) is calculated by reading the difference between the static pressure upstream and downstream of the sample M at the time of collecting performance measurement with the pressure gauge 8 and rounding off the first decimal place of the average value of the three samples. is there.

The nonwoven fabric for filters of the present invention needs to have a bending resistance of 2 to 80 mN. When the bending resistance is less than 2 mN, the strength and form retention of the nonwoven fabric tend to be low, which is not preferable. In particular, it is not preferable because pleat workability is lowered. In consideration of the basis weight and integration method of the nonwoven fabric, it is difficult for the nonwoven fabric for a filter to have a value exceeding 80 mN while satisfying the QF value. A more preferable bending resistance is 2 to 35 mN, a further preferable bending resistance is 2 to 25 mN, and further preferably 5 to 25 mN. Here, the measurement of the bending resistance in the present invention is performed on the Gurley testing machine described in 6.10.3 (a) of JIS-L1085 (1998 edition) (for example, Gurley / flexibility testing machine manufactured by Toyo Seiki Seisakusho Co., Ltd.). Is to be implemented. The bending resistance in the Gurley tester is obtained by the following method. That is, a test piece having a length L = 38.1 mm (effective sample length 25.4 mm) and a width d25.4 mm is taken from an arbitrary 20 points of the sample. Here, in the long-fiber nonwoven fabric, the longitudinal direction of the nonwoven fabric is the length direction of the sample. Each of the collected test pieces is attached to the chuck, and the chuck is fixed in accordance with the scale 1−1 / 2 ″ (1.5 inch = 38.1 mm) on the movable arm A. In this case, the sample length is 1/2 ″. (0.5 inch = 12.7 mm) is 1/4 "(0.25 inch = 6.35 mm) on the chuck, and 1/4" (0.25 inch = 6. 5) on the tip of the pendulum at the free end of the sample. 35 mm), the effective sample length required for measurement is obtained by subtracting ½ ″ (0.5 inch = 12.7 mm) from the test piece length L. Next, the weight mounting hole of the lower part from the fulcrum of the pendulum B Appropriate weights W _a , W _b , W _c (g) are attached to a, b, c (mm), the movable arm A is rotated at a constant speed, and a scale RG (mgf) when the test piece is separated from the pendulum B is obtained. Read the scale with the first decimal place. Although the weight attached to the weight attachment hole can be selected as appropriate, it is preferable to set the scale RG to be 4 to 6. The measurement is performed 5 times for each of the 20 test pieces, 200 times in total. The value of the scale RG is obtained by rounding off the second decimal place by using the following formula: The sample's bending resistance (mN) is the average value of 200 measurements. The following is calculated by rounding off the first place.
Br = RG × (aW _a + bW _b + cW _c ) × (((L-12.7) ² ) / d) × 3.375 × 10 ⁻⁵
The filter nonwoven fabric of the present invention is partially thermocompression bonded, but the method of partially thermocompression bonding is not particularly limited. Bonding with a hot embossing roll or bonding with a combination of an ultrasonic oscillator and an embossing roll is preferred. In particular, adhesion by a hot embossing roll is most preferable from the viewpoint of improving the strength of the nonwoven fabric. The temperature of heat bonding by the hot embossing roll is preferably 5 to 60 ° C., more preferably 10 to 50 ° C. lower than the melting point of the lowest melting point polymer present on the fiber surface of the nonwoven fabric. When the temperature difference between the temperature of heat bonding by the hot embossing roll and the melting point of the polymer having the lowest melting point present on the fiber surface of the nonwoven fabric is less than 5 ° C., the heat bonding tends to be too strong, which is not preferable. If the temperature exceeds 60 ° C., thermal adhesion may be insufficient, which is not preferable.
The pressure-bonding area ratio of the partial thermocompression bonding of the nonwoven fabric for filters of the present invention is a ratio of the total area of the non-woven fabric of the thermocompression bonding portion, and is preferably 5 to 30% with respect to the total area of the nonwoven fabric. If the said crimping | compression-bonding area rate is 5% or more, the intensity | strength of a nonwoven fabric will fully be obtained and the surface will not become fuzzy easily. If the crimping area ratio is 30% or less, the gaps between the fibers are reduced, the pressure loss is increased, and the collection performance is not lowered. A more preferable crimping area ratio is 6 to 20%, and a most preferable crimping area ratio is 8 to 13%.

  The thermocompression bonding part forms a hollow, and is formed by fusing thermoplastic continuous filaments constituting the nonwoven fabric by heat and pressure. That is, the portion where the thermoplastic continuous filament is fused and aggregated as compared with other portions is the thermocompression bonding portion. When adhesion by a hot embossing roll is adopted as a method of thermocompression bonding, a portion where the thermoplastic continuous filaments are fused and aggregated by the convex portion of the embossing roll becomes a thermocompression bonding portion. For example, when a roll having irregularities of a predetermined pattern is used only on the upper side or the lower side and a flat roll having no irregularities is used for the other rolls, the thermocompression bonding part is a convex part of the roll having irregularities and the flat roll. And the portion where the thermoplastic continuous filaments of the nonwoven fabric are aggregated. In addition, for example, it is composed of a pair of upper roll and lower roll having a plurality of parallel grooves arranged on the surface, and the upper roll groove and the lower roll groove intersect at a certain angle. When using the embossing roll provided as described above, the thermocompression bonding portion refers to a portion where the thermoplastic continuous filaments of the nonwoven fabric are aggregated by thermocompression bonding between the convex portion of the upper roll and the convex portion of the lower roll. In this case, the portion that is press-contacted by the upper convex portion and the lower concave portion or the upper concave portion and the lower convex portion is not included in the thermocompression bonding here.

  The shape of the thermocompression bonding part in the non-woven fabric for filter of the present invention is not particularly defined, and a roll having a predetermined pattern of irregularities is used only on the upper side or the lower side, and a flat roll having no irregularities is used for the other rolls. Or a pair of upper and lower rolls having a plurality of parallel grooves arranged on the surface, and the upper roll groove and the lower roll groove intersect at a certain angle. In the embossing roll provided in the above, even when the upper roll convex part and the lower roll convex part are thermocompression bonded, the shape of the thermocompression bonding part is circular, triangular, quadrangular, parallelogram, elliptical A rhombus may be used. The arrangement of these thermocompression bonding portions is not particularly defined, and may be regularly arranged at equal intervals, randomly arranged, or a mixture of different shapes. Among these, from the viewpoint of the uniformity of the nonwoven fabric, those in which the thermocompression bonding portions are arranged at equal intervals are preferable. Furthermore, it consists of a pair of upper rolls and lower rolls in which a plurality of linear grooves arranged in parallel are formed on the surface in terms of partial thermocompression bonding without peeling the nonwoven fabric, and the grooves of the upper rolls The heat of the parallelogram formed by embossing rolls provided so as to intersect with the groove of the lower roll at a certain angle and thermocompression bonding between the convex part of the upper roll and the convex part of the lower roll A crimping part is preferred.

The basis weight of the nonwoven fabric for filters of the present invention is preferably in the range of 90 to 350 g / m ² . When the basis weight is 90 g / m ² or more, rigidity is obtained and the collection performance does not tend to be lowered. If the basis weight is 350 g / m ² or less, the basis weight is too high and the possibility that the pressure loss will increase is low, and further from the viewpoint of cost. A more preferable range of the basis weight is 100 to 320 g / m ² . More preferably, it is 150-260 g / m < ² >. The basis weight here means that three samples of 50 cm in length and 50 cm in width are taken and each weight is measured, the average value of the obtained values is converted per unit area, and the first decimal place is rounded off. Is required.

  Next, the manufacturing method of the nonwoven fabric for filters of this invention is demonstrated.

  The nonwoven fabric for filter of the present invention is preferably a long fiber nonwoven fabric, and the long fiber nonwoven fabric is preferably manufactured by a spunbond method. In a preferred embodiment of the method for producing a nonwoven fabric for a filter according to the present invention, a thermoplastic polymer is melt-extruded from a spinneret, and then pulled and stretched by an air soccer to obtain a thermoplastic continuous filament, which is charged and opened to collect and transfer. A non-woven fabric is formed by depositing on a collecting surface to form a fiber web, pressing the fiber web with a flat roll, and then applying partial thermocompression bonding with a hot embossing roll.

  As the thermoplastic continuous filament, a filament composed of a polyester-based high-melting polymer and a mixed filament composed of a polyester-based low-melting polymer, or a polyester-based low-melting polymer is disposed around the polyester-based high-melting polymer. A composite filament is a preferred form, and most preferred is a method employing a composite filament in which a polyester low-melting polymer is disposed around a polyester high-melting polymer. A composite filament in which a polyester-based low-melting-point polymer is arranged around a polyester-based high-melting-point polymer is integrated with a nonwoven fabric by melt deformation of the low-melting-point polymer component when partially thermocompression bonded by a hot embossing roll. Since the melting point polymer component is not easily damaged by heat, it is easy to integrate the nonwoven fabric, which is preferable.

  In the present invention, the thermoplastic continuous filament is preferably obtained by melting and extruding a thermoplastic polymer from a spinneret and then pulling and stretching with an air soccer.

  By forming the fiber continuous web after electrostatically opening the thermoplastic continuous filament, the number of bundle fibers is reduced, the surface area of the fiber per unit weight is increased, and the collection performance when the nonwoven fabric is obtained is improved. is there. The method for charging the thermoplastic continuous filament is not limited, but charging by a corona discharge method or charging by frictional charging with a metal is preferable. In the corona discharge method, charging is preferably performed at a voltage of −10 to −50 kV.

  The pressure-contact treatment by the flat roll in the method for producing a nonwoven fabric for a filter of the present invention is not limited as long as the flat roll is brought into contact with the fiber web, but the heat treatment for bringing the heated flat roll into contact with the fiber web is performed. preferable. The surface temperature of the flat roll when heat-treated with the heated flat roll is preferably 50 to 180 ° C. lower than the melting point Tm of the resin having the lowest melting point present on the fiber surface of the fiber web. That is, the surface temperature of the flat roll is preferably (Tm-50) ° C to (Tm-180) ° C, more preferably (Tm-60) ° C to (Tm-170) ° C, and (Tm-70) ° C to (Tm). -130) ° C is most preferred. When the temperature of heat processing is lower than (Tm-180) degreeC, the heat processing of a fiber web becomes inadequate and the collection performance improvement effect may become insufficient, and is unpreferable. Further, when the temperature of the heat treatment is higher than (Tm-50) ° C., the heat treatment becomes too strong, and when the heat fusion of the constituent fibers of the surface layer portion is promoted, the number of fused portions increases and the fiber surface area decreases. In this case, the contact area with the dust is reduced, and the collection performance is lowered. Further, if the fibers are fused and the gaps between the fibers are reduced, the pressure loss increases, which is not preferable.

  By press-contact treatment with a flat roll, it is possible to prevent excessive fusion between fibers, the surface area of the fiber is reduced, the effect of preventing the contact area with the dust is reduced and the collection performance is reduced, Improvement in collection performance by heat treatment is sufficient.

  Moreover, 0.1-200 second is a preferable range for the time which heat-processes a flat roll in contact with a fiber web. When the heat treatment time is 0.1 seconds or more, the heat treatment effect of the nonwoven fabric is sufficiently obtained, and the effect of improving the collection performance is sufficient. If the heat treatment time is 200 seconds or less, the heat treatment will not be too strong, and the pressure loss will not be too high. A more preferable heat treatment time is 1 to 100 seconds. A more preferable heat treatment time is 2 to 50 seconds.

  Further, in the method for producing a nonwoven fabric for a filter according to the present invention, the press-contact treatment with the flat roll is performed by press-contacting the fiber web with a pair of flat rolls to form a non-woven fabric. The method of contacting the roll is most preferable. That is, a method in which a fibrous web is heated and pressed by a pair of flat rolls to form a nonwoven fabric, and one side of the nonwoven fabric is continuously brought into contact with one of the rolls of the pair of flat rolls from a heating and pressing portion, and heat treatment is preferable. Is. As a method of contacting, the method shown in FIG. 2 is generally used, but as shown in FIGS. 3 and 4, it is a method of winding a pair of flat rolls in an S-shape or an inverted S-shape. However, what is necessary is just to be able to make one roll of a pair of said flat roll contact continuously from a heating press-contact part, and to heat-process. The linear pressure at the time of press-contact with a pair of flat rolls is preferably in the range of 1 to 100 kg / cm, more preferably in the range of 2 to 80 kg / cm. If the linear pressure is 1 kg / cm or more, a sufficient linear pressure for sheet formation can be obtained. When the linear pressure is 100 kg / cm or less, the adhesion of the nonwoven fabric does not become too strong, and therefore the pressure loss does not become too high.

  Furthermore, it is preferable that the contact by the continuous flat roll from the heat-welded part of the nonwoven fabric is performed in a state where a tension of 5 to 200 N / m is applied in the running direction of the nonwoven fabric. A tension of 5 N / m or more is preferable because the tendency of the nonwoven fabric to be wound around the flat roll is reduced. If the tension is 200 N / m or less, the nonwoven fabric is less likely to be cut, which is a preferred direction. A more preferable tension range is 8 to 180 N / m.

  Furthermore, when making the said nonwoven fabric contact a flat roll continuously from a heating press-contacting part, the range of 2-250 cm is preferable. When the contact distance is 2 cm or more, the heat treatment effect is sufficient, and the collection performance is sufficiently obtained. If the contact distance is 250 cm or less, the heat treatment becomes too strong and the pressure loss does not increase. A more preferable contact distance is in the range of 4 to 200 cm.

  Since the nonwoven fabric for filters of the present invention is excellent in rigidity, it can be easily processed into a pleated shape and has excellent pleated form retention. Therefore, the filter nonwoven fabric of the present invention is preferably used as a pleated filter.

  The use of the non-woven fabric for filter of the present invention is not limited at all, but it is preferably used as an industrial filter because of its excellent mechanical strength and rigidity and excellent dust collection performance. Particularly preferably, the pleated cylindrical unit is used for cleaning a bag filter such as a dust collector or a liquid filter such as an electric discharge machine, and further used for cleaning intake air of a gas turbine or an automobile engine. It is used for an intake filter. In particular, in a bag filter for a dust collector, the non-woven fabric of the present invention having excellent strength is preferable because it removes dust accumulated on the filter surface layer during use, and is subjected to a removal process with backwash air.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited by these Examples. In addition, each characteristic value in the following Example is measured by the following method.

(1) Melting point (° C)
Using a differential scanning calorimeter DSC-2 manufactured by Perkin Elma Co., Ltd., measurement was performed under the condition of a temperature rising rate of 20 ° C./min. Further, for a resin whose melting endotherm curve does not show an extreme value in a differential scanning calorimeter, the resin was heated on a hot plate and the temperature at which the resin was melted by microscopic observation was taken as the melting point.

(2) Intrinsic viscosity IV
The intrinsic viscosity of the polyester was measured by the following method.
8 g of a sample was dissolved in 100 ml of orthochlorophenol, and a relative viscosity η _r was determined by the following formula using an Ostwald viscometer at a temperature of 25 ° C.
η _r = η / η ₀ = (t × d) / (t ₀ × d ₀ )
Where η: viscosity of the polymer solution
η ₀ : viscosity of orthochlorophenol
t: Dropping time of solution (second)
d: density of the solution (g / cm ³ )
t ₀ : Fall time of orthochlorophenol (seconds)
d ₀ : Orthochlorophenol density (g / cm ³ )
Subsequently, the intrinsic viscosity IV was calculated from the relative viscosity η _{r by the} following formula.
IV = 0.0242η _r +0.2634
(3) Fineness (decitex)
Ten small sample samples are taken at random from the nonwoven fabric, photographed at 500 to 3000 times with a scanning electron microscope, 10 fibers are selected from each sample, a total of 100 fibers are selected, and the thickness is measured. . The fiber is assumed to have a circular cross section, and the thickness is the fiber diameter. The fineness is calculated from the fiber diameter calculated by rounding off the first decimal place of the average value and the density of the polymer, and the first decimal place is rounded off.

(4) Weight per unit (g / m ² )
Three samples each having a length of 50 cm and a width of 50 cm were taken, the weight of each sample was measured, the average value of the obtained values was converted per unit area, and the first decimal place was rounded off.

(5) Tensile strength (N / 5cm)
A sample with a sample size of 5 cm × 30 cm is subjected to a tensile test with a constant-speed extension type tensile tester for three samples in the longitudinal and lateral directions under the conditions of a gripping interval of 20 cm and a tensile speed of 10 cm / min, and the sample breaks. The maximum strength when pulled to the maximum was taken as the tensile strength. The average value in the longitudinal and lateral directions of the sheet was calculated by rounding off the first decimal place.

(6) Collection performance (%), pressure loss (Pa), QF value (Pa ⁻¹ )
The dust collection performance was measured by the following method.

Three samples of 15 cm × 15 cm were collected from an arbitrary portion of the nonwoven fabric, and the collection performance of each sample was measured with the collection performance measuring device shown in FIG. This collection performance measuring apparatus has a configuration in which a dust storage box 2 is connected to the upstream side of a sample holder 1 for setting a measurement sample M, and a flow meter 3, a flow rate adjusting valve 4 and a blower 5 are connected to the downstream side. Yes. Further, the particle counter 6 is connected to the sample holder 1, and the number of dusts on the upstream side and the number of dusts on the downstream side of the measurement sample M can be measured via the switching cock 7. In measuring the collection efficiency, a 10% by weight polystyrene 0.309U solution (manufactured by Nacalai Tech) is diluted 200 times with distilled water and filled in the dust storage box 2. Next, the sample M is set in the holder 1, and the air volume is adjusted by the flow rate adjusting valve 4 so that the filter passing speed is 3.0 m / min, and the dust concentration is 20,000 to 70,000 pieces / (2.83 × 10 ⁻⁴ m ³ (0.01 ft ³ )), the dust number D2 upstream of the sample M and the dust number D1 downstream are sampled by a particle counter 6 (manufactured by Lion Co., Ltd., KC-01D) with a dust particle size of 0.1. Each of the ranges of 3 to 0.5 μm was measured, and the collection efficiency (%) was obtained by rounding off the first decimal place of the numerical value obtained by the following formula.

Collection efficiency (%) = [1- (D1 / D2)] × 100
Here, D1: downstream dust count (total of 3 times)
D2: Number of upstream dust (total of 3 times)
The pressure loss (Pa) was calculated by reading the static pressure difference between the upstream and downstream of the sample M at the time of the collection performance measurement with the pressure gauge 8 and rounding off the first decimal place of the average value of the three samples.

Further, the QF value is obtained by the following equation using the collection performance and pressure loss value obtained by the above method:
QF value (Pa ⁻¹ ) = − [ln (1- [collecting performance (%)] / 100)] / [pressure loss (Pa)]
And rounded off to the second decimal place.

(7) Bending softness (mN)
The measurement of the bending resistance was carried out with a Gurley tester (Gare / flexibility tester manufactured by Toyo Seiki Seisakusyo Co., Ltd.) described in 6.10.3 (a) of JIS-L1085 (1998 edition). The bending resistance with a Gurley tester was determined by the following method. That is, a test piece having a length L38.1 mm (effective sample length 25.4 mm) and a width d25.4 mm is taken from any 20 points of the sample. Here, in the long-fiber nonwoven fabric, the longitudinal direction of the nonwoven fabric is the length direction of the sample. Each of the collected test pieces is attached to the chuck, and the chuck is fixed in accordance with the scale 1−1 / 2 ″ (1.5 inch = 38.1 mm) on the movable arm A. In this case, the sample length is 1/2 ″. (0.5 inch = 12.7 mm) is 1/4 "(0.25 inch = 6.35 mm) on the chuck, and 1/4" (0.25 inch = 6. 5) on the tip of the pendulum at the free end of the sample. 35 mm), the effective sample length required for measurement is obtained by subtracting ½ ″ (0.5 inch = 12.7 mm) from the test piece length L. Next, the weight mounting hole of the lower part from the fulcrum of the pendulum B Appropriate weights W _a , W _b , W _c (g) are attached to a, b, c (mm), the movable arm A is rotated at a constant speed, and a scale RG (mgf) when the test piece is separated from the pendulum B is obtained. Read the scale with the first decimal place. Weight attached to weight mounting holes in was set so that the scale RG is 4 to 6. Measurements sides each 5 times for the test piece 20 points, carried a total of 200 times. Below from the obtained values of the scale RG type,
Br = RG × (aW _a + bW _b + cW _c ) × (((L-12.7) ² ) / d) × 3.375 × 10 ⁻⁵
Calculate the bending resistance value by rounding off to the second decimal place. The bending resistance (mN) of the sample is calculated by rounding the average value of 200 measurements to the first decimal place.

Example 1
Polyethylene terephthalate (PET) having an intrinsic viscosity of IV0.65 and a melting point of 260 ° C. dried to a moisture content of 50 wt ppm or less, an intrinsic viscosity IV0.66 dried to a moisture content of 50 wt ppm or less, and an isophthalic acid copolymerization ratio of 11 mol%. A copolymer polyester (CO-PET) having a melting point of 230 ° C. is melted at 295 ° C. and 280 ° C., respectively, using polyethylene terephthalate as a core component and copolymer polyester as a sheath component, a die temperature of 300 ° C., core: sheath = 80: 20 After spinning from the pores at a weight ratio of 1, a filament having a circular cross section is spun at a spinning speed of 4300 m / min by air soccer, and the fiber is charged and opened at a voltage of −30 kV by the corona discharge method to move. It was collected as a fiber web on a net conveyor. The collected fiber web was heated and pressed with a flat roll on a net conveyor at a temperature of 80 ° C. and a linear pressure of 10 kg / cm, and the sheet was continuously brought into contact with the flat roll for 4 cm, and then arranged in parallel on the surface. An embossing roll comprising a pair of upper rolls and lower rolls in which straight grooves are formed, and the upper roll groove and the lower roll groove crossing at a certain angle. The embossing roll was thermocompression bonded with the convex part of the lower roll and the convex part of the lower roll, and the pressure bonding area ratio was adjusted to 10%, and thermocompression bonding was performed at a temperature of 180 ° C. and a linear pressure of 70 kg / cm. A spite bond nonwoven fabric having a decitex and a basis weight of 260 g / m ² was obtained.

Example 2
Polyethylene terephthalate (PET) having an intrinsic viscosity of IV0.65 and a melting point of 260 ° C. dried to a moisture content of 50 wt ppm or less, an intrinsic viscosity IV0.66 dried to a moisture content of 50 wt ppm or less, and an isophthalic acid copolymerization ratio of 11 mol%. Copolyester (CO-PET) having a melting point of 230 ° C. is melted at 295 ° C. and 280 ° C., respectively, and a spinneret (polyethylene terephthalate: polyethylene terephthalate) in which discharge holes are arranged so as to be discharged from different discharge holes, respectively. After spinning at a die temperature of 295 ° C. with a copolyester = 8: 2 ratio), a filament having a circular cross-sectional shape was spun at a spinning speed of 4500 m / min by air soccer, and a corona discharge method was used. The fibers were charged and opened at a voltage of −30 kV and collected as a fiber web on a moving net conveyor. The collected fiber web is heated and pressed with a pair of flat rolls at a temperature of 130 ° C. and a linear pressure of 60 kg / cm, and the sheet is continuously brought into contact with the flat rolls for 120 cm, and then a plurality of straight lines arranged in parallel on the surface. In the embossing roll provided with a pair of upper and lower rolls in which a groove is formed, the groove of the upper roll and the groove of the lower roll intersect at a certain angle. The embossing roll is thermocompression bonded between the convex part and the convex part of the lower roll, and the crimping area ratio is adjusted to 10%, and thermocompression bonding is performed at a temperature of 190 ° C. and a linear pressure of 80 kg / cm, and the fineness is 3 dtex. A spunbonded nonwoven fabric having a basis weight of 260 g / m ² was obtained.

Example 3
A spunbonded nonwoven fabric was obtained in the same manner as in Example 1 except that the basis weight was 200 g / m ² .
Example 4
Polyethylene terephthalate (PET) having an intrinsic viscosity of IV0.65 and a melting point of 260 ° C. dried to a moisture content of 50 wt ppm or less, an intrinsic viscosity IV0.66 dried to a moisture content of 50 wt ppm or less, and an isophthalic acid copolymerization ratio of 11 mol%. A copolymer polyester (CO-PET) having a melting point of 230 ° C. is melted at 295 ° C. and 280 ° C., respectively, using polyethylene terephthalate as a core component and copolymer polyester as a sheath component, a die temperature of 300 ° C., core: sheath = 80: 20 After spinning from the pores at a weight ratio of, a filament having a circular cross-section was spun by air soccer at a spinning speed of 4300 m / min, the filament collided with a metal collision plate installed at the air soccer outlet, and the fiber by friction charging Were charged and opened, and collected as a fiber web on a moving net conveyor. The collected fiber web was heated and pressed with a flat roll on a net conveyor at a temperature of 120 ° C. and a linear pressure of 50 kg / cm, and the sheet was continuously brought into contact with the flat roll for 120 cm, and then arranged in parallel on the surface. An embossing roll comprising a pair of upper rolls and lower rolls in which straight grooves are formed, and the upper roll grooves and lower roll grooves cross each other at a fixed angle. The embossing roll is thermocompression-bonded between the convex part of the roll and the convex part of the lower roll, and the crimping area ratio is adjusted to 10%, and thermocompression bonding is performed at a temperature of 200 ° C. and a linear pressure of 70 kg / cm. A spunbonded nonwoven fabric with 3 dtex and a basis weight of 260 g / m ² was obtained.

The properties of the obtained nonwoven fabric are as shown in Table 1, but the nonwoven fabrics of Examples 1, 2, 3, and 4 were all excellent in tensile strength and bending resistance. Moreover, since it was excellent also in collection performance and pressure loss, QF value (Pa < ^-1 >) was as favorable as 0.03, 0.04, 0.05, and 0.04, respectively.

Comparative Example 1
Polyethylene terephthalate (PET) having an inherent viscosity of 0.65 and a melting point of 260 ° C. dried to a moisture content of 50 ppm by weight or less is melted at 295 ° C., spun from the pores at a die temperature of 300 ° C., and then spun at 4400 m by air soccer. A filament having a circular cross-sectional shape was spun at / min, and the fiber was charged and opened at a voltage of −30 kV by a corona discharge method, and collected as a fiber web on a moving net conveyor. The embossed roll was adjusted so that the crimped area ratio was 16% using a roll having a circular convex part on the upper side and a flat roll having no concaves and convexes on the lower side. thermocompression bonding under the conditions of pressure of 60 kg / cm, to obtain a fineness of 2 dtex and a basis weight of 260 g / ^{m 2} spunbond nonwoven.

Comparative Example 2
Polyethylene terephthalate (PET) having an intrinsic viscosity of IV0.65 and a melting point of 260 ° C. dried to a moisture content of 50 wt ppm or less, an intrinsic viscosity IV0.66 dried to a moisture content of 50 wt ppm or less, and an isophthalic acid copolymerization ratio of 11 mol%. A copolymer polyester (CO-PET) having a melting point of 230 ° C. is melted at 295 ° C. and 280 ° C., respectively, using polyethylene terephthalate as a core component and copolymer polyester as a sheath component, a die temperature of 300 ° C., core: sheath = 80: 20 After spinning from the pores at a weight ratio of 1, a filament having a circular cross section was spun at a spinning speed of 4300 m / min by air soccer and collected as a fiber web on a moving net conveyor. The embossed roll, in which the collected fiber web is adjusted to have a crimp area ratio of 18% using a roll having a circular convex part on the upper side and a flat roll having no concaves on the lower side, has a temperature of 200 ° C., a line thermocompression bonding under the conditions of pressure of 70 kg / cm, to obtain a fineness of 2 dtex and a basis weight of 260 g / ^{m 2} spunbond nonwoven.

Comparative Example 3
Polyethylene terephthalate (PET) having an inherent viscosity of 0.65 and a melting point of 260 ° C. dried to a moisture content of 50 ppm by weight or less is melted at 295 ° C., spun from the pores at a die temperature of 300 ° C., and then spun at 4400 m by air soccer. A filament having a circular cross-sectional shape was spun at / min and collected as a fiber web on a moving net conveyor. The embossed roll, in which the collected fiber web is adjusted so that the crimping area ratio is 3%, using a roll having a circular convex part on the upper side and a flat roll having no concaves on the lower side, is set at a temperature of 180 ° C. thermocompression bonding under the conditions of pressure of 30kg / cm, to obtain a fineness of 3 dtex, spunbonded nonwoven fabric having a basis weight of 200 g / ^{m 2.}

Comparative Example 4
Polyethylene terephthalate (PET) having an intrinsic viscosity of IV0.65 and a melting point of 260 ° C. dried to a moisture content of 50 wt ppm or less, an intrinsic viscosity IV0.66 dried to a moisture content of 50 wt ppm or less, and an isophthalic acid copolymerization ratio of 11 mol%. A copolymer polyester (CO-PET) having a melting point of 230 ° C. is melted at 295 ° C. and 280 ° C., respectively, using polyethylene terephthalate as a core component and copolymer polyester as a sheath component, a die temperature of 300 ° C., a core: sheath = 20: 80. After spinning from the pores at a weight ratio of 1, a filament having a circular cross section was spun at a spinning speed of 4300 m / min by air soccer and collected as a fiber web on a moving net conveyor. The embossed roll, in which the collected fiber web is adjusted so that the crimping area ratio is 50% using a roll having a circular convex part on the upper side and a flat roll having no concave part on the lower side, is set at a temperature of 200 ° C. thermocompression bonding under the conditions of pressure of 70 kg / cm, to obtain a fineness of 2 dtex and a basis weight of 260 g / ^{m 2} spunbond nonwoven.

Comparative Example 5
Polyethylene terephthalate (PET) having an intrinsic viscosity of IV0.65 and a melting point of 260 ° C. dried to a moisture content of 50 wt ppm or less, an intrinsic viscosity IV0.66 dried to a moisture content of 50 wt ppm or less, and an isophthalic acid copolymerization ratio of 11 mol%. A copolymer polyester (CO-PET) having a melting point of 230 ° C. is melted at 295 ° C. and 280 ° C., respectively, using polyethylene terephthalate as a core component and copolymer polyester as a sheath component, a die temperature of 300 ° C., core: sheath = 80: 20 After spinning from the pores at a weight ratio of 1, a filament having a circular cross-sectional shape is spun by air soccer at a spinning speed of 4400 m / min, and the fiber is charged and opened at a voltage of −30 kV by the corona discharge method and moved. It was collected as a fiber web on a net conveyor. The embossed roll was adjusted so that the crimped area ratio was 16% using a roll having a circular convex part on the upper side and a flat roll having no concaves and convexes on the lower side. After thermocompression bonding under the condition of a pressure of 60 kg / cm, a pair of flat rolls were heated and pressed at a temperature of 205 ° C. and a linear pressure of 50 kg / cm, and the sheet was continuously brought into contact with the flat rolls for 120 cm, a fineness of 2 dtex and a basis weight of 260 g / cm A spunbond nonwoven fabric of m ² was obtained.

The properties of the obtained nonwoven fabric are as shown in Table 1, but the nonwoven fabrics of Comparative Examples 1, 2, 4, and 5 were all excellent in tensile strength and bending resistance. However, the QF value (Pa ⁻¹ ) obtained from the collection performance and pressure loss is 0.01, which is inferior to the performance as a filter. Further, the nonwoven fabric of Comparative Example 3 had insufficient thermal adhesion, had low tensile strength, and had low bending resistance. Further, the QF value (Pa ⁻¹ ) was as low as 0.01, and the performance as a filter was inferior.

  The non-woven fabric for filters of the present invention is excellent in dust collection performance, has a low pressure loss, and is excellent in mechanical properties and rigidity, so that it can be suitably used particularly as an industrial air filter or liquid filter. .

It is the schematic of a collection performance measuring device. It is the schematic of an example which heat-processes a fiber web with a pair of flat roll. It is the schematic of an example which heat-processes a fiber web with a pair of flat roll. It is the schematic of an example which heat-processes a fiber web with a pair of flat roll.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample holder 2 Dust storage box 3 Flowmeter 4 Flow control valve 5 Blower 6 Particle counter 7 Switching cock 8 Pressure gauge M Measurement sample 9 Flat roll 10 Fiber web (nonwoven fabric)
11 Heating pressure contact part 12 Contact part of nonwoven fabric and flat roll

Claims (10)

A long fiber obtained by press-bonding a fiber web made of thermoplastic continuous filaments with a flat roll under a surface temperature of (Tm-50) ° C. to (Tm-180) ° C. and then partially thermocompression bonding with a hot embossing roll. A non-woven fabric for a filter, having a QF value (Pa ^-1 ) of 0.02 to 0.08 and a bending resistance of 2 to 80 mN.
Tm represents the melting point of the resin having the lowest melting point present on the fiber surface of the fiber web. The nonwoven fabric for filters according to claim 1, wherein the bending resistance is 2 to 25 mN. The nonwoven fabric for a filter according to claim 1 or 2, wherein the thermoplastic continuous filament is composed of a composite filament in which a polyester low-melting polymer is disposed around a polyester high-melting polymer. 3. The filter according to claim 1, wherein the thermoplastic continuous filament is composed of a mixed filament of a filament made of a polyester-based high melting point polymer and a filament made of a polyester-based low melting point polymer. Nonwoven fabric. The non-woven fabric for a filter according to any one of claims 1 to 4, wherein the non-woven fabric for a filter according to any one of claims 1 to 4, wherein the non-woven fabric for a filter is partially thermocompression bonded at a pressure bonding area ratio of 5 to 30%. The filter nonwoven fabric according to any one of claims 1 to 5, which is processed into a pleated shape. After the thermoplastic polymer is melt extruded from the spinneret, it is pulled and stretched by air soccer to make a thermoplastic continuous filament, which is charged and opened and deposited on the moving collection surface to form a fiber web. A long-fiber non-woven fabric is formed by subjecting a fiber web to pressure contact with a flat roll under a condition of a surface temperature of (Tm-50) ° C. to (Tm-180) ° C. and then applying partial thermocompression with a hot embossing roll. The manufacturing method of the nonwoven fabric for filters characterized by these.
Tm represents the melting point of the fiber web and the resin having the lowest melting point present on the fiber surface of the fiber web. 8. The method for producing a nonwoven fabric for a filter according to claim 7, wherein the thermoplastic continuous filament is a composite filament in which a polyester low-melting polymer is disposed around a polyester high-melting polymer. 8. The method for producing a nonwoven fabric for a filter according to claim 7, wherein the thermoplastic continuous filament is a filament made of a polyester high-melting polymer and a mixed filament made of a polyester low-melting polymer. The press-contact treatment with the flat roll is characterized in that the fibrous web is heated and pressed by a pair of flat rolls to form a nonwoven fabric, and the nonwoven fabric is continuously brought into contact with the flat roll from the heated and pressed portion. The manufacturing method of the nonwoven fabric for filters in any one of claim | item 7 -9.

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