JP5585274B2 - Manufacturing method of long fiber nonwoven fabric for heat resistant filter - Google Patents

Description

The present invention relates to a manufacturing method of the pleat form stability and heat resistance of heat resistant filter for long fibrous nonwoven fabric having both at high temperatures.

  Conventionally, for example, polyphenylene sulfide (hereinafter sometimes abbreviated as PPS) short fibers are mainly used for heat-resistant filters that collect dust such as garbage incinerators and coal boilers whose exhaust gas temperature is 140 to 200 ° C. A filter is used in which a fiber felt made of is sewn into a cylindrical shape.

  However, in recent years, there has been an increasing demand for filtering as much exhaust gas as possible in a limited space, and there is a need for a pleated heat-resistant filter that can have a larger filtration area than a filter sewn in a cylindrical shape. It has been. However, in the conventional fiber felt made of short PPS fibers, because the constituent fibers are short fibers and the form is maintained by the needle punch, it is rigid and flexible, so that it has a pleated shape. There was a problem that it could not be processed.

  So far, various proposals have been made for pleating a nonwoven fabric made of PPS fibers and using it as a heat resistant filter.

  For example, it has been proposed that PPS resin is spun and stretched by a spunbond method, subjected to heat treatment for dimensional stabilization against heat under tension, and then the bonded non-woven fabric is used as a pleated filter material. (See Patent Document 1). Certainly, the PPS long fiber nonwoven fabric proposed here has high rigidity at room temperature and excellent pleatability. However, in this proposal, the PPS fibers constituting the nonwoven fabric are softened at a high temperature, the pleated form of the nonwoven fabric cannot be maintained, the adjacent pleats closely contact each other, the filtration area is reduced, and the pressure loss of the filter There was a problem that the skyrocketed.

  On the other hand, proposals for improving softening of PPS fibers at high temperatures have also been made. For example, by impregnating a non-woven fabric made of PPS fibers with a thermosetting resin such as an epoxy resin or a phenol resin, the non-woven fabric is not easily softened even at high temperatures, and pleated form retention at high temperatures may be improved. It has been proposed (see Patent Document 2 and Patent Document 3). Certainly, in these proposals, since the PPS fiber is not easily softened even at high temperatures, an effect excellent in pleat shape retention is exhibited. However, when the thermosetting resin is used for a long period of time, the thermosetting resin deteriorates thermally, so that the mechanical strength of the nonwoven fabric is greatly reduced and the filter is damaged. It was.

JP 2008-223209 A Japanese Patent No. 4110628 Japanese Patent No. 3989797

It is an object of the present invention, in view of the problems of the prior art and to provide a method of manufacturing a pleated form stability and long-term heat resistance heat resistance filter for long fibrous nonwoven fabric which is excellent in both of a high temperature .

This invention solves the said subject, and the manufacturing method of the long-fiber nonwoven fabric for heat resistant filters of this invention is 200-280 degreeC in the fiber web comprised from the long fiber which has polyphenylene sulfide as a main component. And then heat-treating at a temperature of 250 to 280 ° C. and a time of 1 minute to 24 hours .

  According to the present invention, it is possible to obtain a long-fiber nonwoven fabric for a heat-resistant filter that is excellent in pleat form retention even at high temperatures, has little decrease in mechanical strength even when used at high temperatures for a long period of time, and is excellent in heat resistance.

The long-fiber nonwoven fabric for heat-resistant filters obtained by the present invention is excellent in pleat form retention at high temperatures and long-term heat resistance, and therefore can be suitably used as a pleated heat-resistant filter.

FIG. 1 is a side view for explaining the means for measuring the sagging length of the present invention.

  Next, the form for implementing this invention is demonstrated in detail.

The long-fiber non-woven fabric for heat-resistant filter obtained by the present invention is composed of a non-woven fabric composed of long fibers mainly composed of polyphenylene sulfide, has a sag length of 40 mm or less at normal temperature, and at normal temperature and 170 ° C. A long-fiber non-woven fabric for a heat-resistant filter, characterized in that a difference in sagging length is 35 mm or less.

That is, in the long-fiber nonwoven fabric for heat-resistant filters obtained by the present invention, it is important that the sagging length at room temperature is 40 mm or less, and the difference in sagging length between room temperature and 170 ° C. is 35 mm or less. It is.

  In the present invention, when the sagging length at room temperature is 40 mm or less, more preferably 30 mm or less, and even more preferably 20 mm or less, excellent rigidity is exhibited and pleat workability is improved. Furthermore, the difference in the length of sag between normal temperature and 170 ° C. is 35 mm or less, more preferably 30 mm or less, and even more preferably 25 mm or less. It is possible to make a long-fiber nonwoven fabric excellent in. Regarding the difference between the sagging length at room temperature and the sagging length at room temperature and 170 ° C., the lower limit is not particularly defined but is 0 mm or more.

  The sagging length in the present invention is an index indicating rigidity and softening, and the test method for measuring the sagging length is as follows. FIG. 1 is a side view for explaining the means for measuring the sagging length of the present invention.

  First, a measurement piece having a length of 200 mm and a width of 20 mm is cut out from the nonwoven fabric whose sagging length is to be measured. As shown in FIG. 1, the manufactured measurement piece 1 is fixed to the upper surface of the rectangular measurement piece mounting block 3 by a mechanical means or an adhesive at a portion 100 mm from one end 2 of the measurement piece 1. At this time, the other end of the measurement piece 1 protrudes from the block 3. Under this condition, the length L0 in the vertical direction between the protruding tip of the measurement piece 1 and the upper surface of the mounting block (“the hanging length at normal temperature” in the present invention) is measured. After the measurement, the block 3 on which the measurement piece 1 is set is left in an atmosphere at a temperature of 170 ° C. for 1 hour. During this time, the portion protruding from the block 3 of the measurement piece 1 softens and hangs down. For the measurement piece 4 (drawn with a dotted line in FIG. 1) after one hour has elapsed, the length L1 in the vertical direction between the protruding tip and the upper surface of the mounting block 3 is measured. The length L2 obtained by subtracting L0 from the measured L1 (the “difference in sagging length between normal temperature and 170 ° C.” in the present invention) is obtained. This measurement is measured and averaged on the front and back of the nonwoven fabric (each n = 2), and the values of L0 and L2 are obtained by rounding off the first decimal place. Depending on the size of L0 and L2, the stiffness of the nonwoven fabric at room temperature and the softening at high temperature, that is, the shape retention of the pleats at high temperature can be evaluated. The direction of the nonwoven fabric that satisfies both the “hanging length at normal temperature” and the “difference in hanging length at normal temperature and 170 ° C.” as specified in the present invention is the horizontal direction (machine traveling direction). The direction (machine width direction) does not matter, and it is important to be satisfied in at least one direction.

  Moreover, the normal temperature said by this invention shall be 20 degreeC, and it can accept | permit to about +/- 15 degreeC as measurement conditions.

The long-fiber nonwoven fabric for heat-resistant filters obtained by the present invention does not require a thermosetting resin that has been conventionally used to suppress softening of PPS fibers at high temperatures. That is, in this invention, it is a preferable aspect that the thermosetting resin has not adhered to the long-fiber nonwoven fabric for heat resistant filters.

  However, as long as the effect of the present invention is not impaired, the thermosetting resin can be fixed to the long-fiber nonwoven fabric of the present invention to maintain rigidity at a higher temperature. It is within the scope of the present invention. It is preferable that the solid content fixing rate with respect to the long-fiber nonwoven fabric of a thermosetting resin is 5-30 mass% with respect to 100 mass% of long-fiber nonwoven fabric. By setting it as 5 mass% or more, it is excellent in the pleat form retention property at the time of high temperature, and by making solid content fixation rate 30 mass% or less, it can be excellent in air permeability and can be made a low pressure loss.

  However, since the PPS long fiber nonwoven fabric to which the thermosetting resin is fixed is used for a long period of time at a high temperature, the resin component undergoes thermal deterioration, and the mechanical strength of the PPS long fiber nonwoven fabric itself is greatly reduced. It is preferable not to use a thermosetting resin. Examples of the thermosetting resin include an epoxy resin, a phenol resin, and an amino resin.

  The thermosetting resin is fixed by impregnating a solution containing the thermosetting resin with a dip mangle, and drying and curing the nonwoven fabric impregnated with the thermosetting resin with a pin tenter or clip tenter as appropriate. Can be achieved.

The long-fiber nonwoven fabric for heat-resistant filters obtained by the present invention has a temperature of 210 ° C. in 1500 hours in the air in any one of the vertical direction (machine traveling direction) and the horizontal direction (machine width direction) of the nonwoven fabric. The tensile strength retention in the heat exposure test is preferably 80% or more. If the tensile strength retention is 80% or more, more preferably 85% or more, and even more preferably 90% or more, even if the heat resistant filter is used at a high temperature for a long period of time, tears and cracks associated with a decrease in strength of the nonwoven fabric may occur. It tends to be less likely to occur. The upper limit of the tensile strength retention is not particularly defined, but is preferably 150% or less.

  In the present invention, the resin used for the heat-resistant filter long fiber is mainly composed of PPS. PPS has phenylene sulfide units such as p-phenylene sulfide units and m-phenylene sulfide units as repeating units. Among them, a resin containing 90 mol% or more of p-phenylene sulfide units has a molecular chain substantially linear, and is preferably used from the viewpoints of heat resistance and spinnability. Examples of commercially available products include Torelina E2280, E2481, and E2180 manufactured by Toray.

  The PPS content in the resin containing PPS as a main component used in the present invention (hereinafter sometimes referred to as PPS resin) is preferably 85% by mass or more, more preferably from the viewpoint of heat resistance and chemical resistance. Is 90 mass% or more, more preferably 95 mass% or more. Materials added to the PPS resin include polyolefins such as polyethylene and polypropylene, polyamides such as nylon 6, nylon 6/6, nylon 6/10, nylon 6/12, polyethylene terephthalate, and polybutylene terephthalate. Polyesters such as polycyclohexine dimethylene terephthalate, polyether ether ketones, polyether imides, and modified polyphenylene sulfides can be used, but are not necessarily limited thereto.

  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 PPS resin as long as the effects of the present invention are not impaired.

  The PPS resin used in the present invention is a melt flow rate (hereinafter abbreviated as MFR) measured according to ASTM D1238-70 (measurement temperature 315.5 ° C., measurement load 5 kg load, unit g / 10 min). Is preferably 100 to 300 g / 10 min. A high MFR means that the fluidity of the resin is high, and in order to obtain the strength and heat resistance of the fiber, a low MFR with a high degree of polymerization of PPS is preferable, but the MFR is 100 g / 10 min or more, More preferably, by setting it to 140 g / 10 min or more, an increase in the back pressure of the spinneret can be suppressed, and a decrease in spinnability, that is, yarn breakage can be suppressed. On the other hand, when the MFR is 300 g / 10 min or less, more preferably 225 g / 10 min or less, the strength and heat resistance of the fiber can be maintained to a certain extent.

  As the cross-sectional shape of the long fiber mainly composed of PPS used in the present invention, any of circular shape, hollow round shape, elliptical shape, flat shape, irregular shape such as X shape and Y shape, polygonal shape, and multileaf shape, etc. It may be a shape.

  Moreover, it is preferable that the average single fiber fineness of the long fiber which has PPS as a main component is the range of 0.5-10 dtex. By setting the average single fiber fineness of the long fibers mainly composed of PPS to 0.5 dtex or more, more preferably 1 dtex or more, and further preferably 2 dtex or more, air permeability is excellent and low pressure loss can be achieved. On the other hand, when the average single fiber fineness of the long fibers mainly composed of PPS is 10 dtex or less, more preferably 6 dtex or less, and further preferably 4 dtex or less, dust collection efficiency can be increased.

The basis weight of the long-fiber nonwoven fabric for heat-resistant filters obtained by the present invention is preferably in the range of 50 to 500 g / m ² . By setting the basis weight to 50 g / m ² or more, preferably 100 g / m ² or more, and more preferably 200 g / m ² or more, the rigidity is excellent and the pleat workability is good. On the other hand, when the basis weight is 500 g / m ² or less, more preferably 400 g / m ² or less, and even more preferably 300 g / m ² or less, the air permeability is excellent and the low pressure loss can be achieved.

  Next, the manufacturing method of the long fiber nonwoven fabric for heat resistant filters of this invention is demonstrated.

  In the method for producing a long-fiber nonwoven fabric for heat-resistant filters of the present invention, it is important to heat-treat a fiber web composed of long fibers mainly composed of polyphenylene sulfide at a temperature of 200 to 280 ° C. It is.

  Examples of the method for producing the long-fiber nonwoven fabric in the present invention include a spunbond method and a melt blow method, but the spunbond method is preferably used from the viewpoint of excellent rigidity and mechanical strength.

  As an example of the process in the spunbond method, a resin mainly composed of PPS is melted, discharged from a spinneret, and then cooled and solidified by an ejector, stretched, and captured on a moving net. A process of collecting and forming a fibrous web and then heat-bonding may be mentioned.

  Conventionally, when a long-fiber nonwoven fabric mainly composed of PPS is produced by the spunbond method, a web that is easily contracted to heat can be obtained because PPS fibers do not undergo sufficient orientation crystallization in the spinning process. is there. In this case, before heat-bonding the fiber web, a tension heat treatment may be performed for a very short time with a pin tenter or the like with the aim of suppressing shrinkage of the fiber web against heat while maintaining the heat-bonding property.

  In the present invention, it does not matter at all to carry out heat treatment for the purpose of achieving both thermal adhesiveness and dimensional stability against heat. However, the heat treatment referred to in the present invention is not intended for dimensional stabilization against heat, but for a nonwoven fabric that has already sufficiently achieved dimensional stabilization against heat, pleated form retention at high temperatures. It is carried out with the intention of enhancing. For this reason, it is very important that the heat treatment referred to in the present invention is performed after the thermal bonding step. The heat treatment referred to in the present invention does not include thermal bonding for the purpose of fusing and integrating the fibers, but refers to a treatment for improving the crystallinity of the nonwoven fabric.

  If the heat treatment aiming at the effect of the present invention is performed before the heat bonding step, the crystallinity of the PPS long fibers becomes too high, the heat bonding cannot be performed, the mechanical strength becomes very weak, and it is difficult to withstand practical use. Only non-woven fabric can be obtained.

  The timing for performing the heat treatment in the present invention may be after the thermal bonding treatment, for example, after the thermal bonding, the thermal processing is performed continuously, or the thermal processing is performed after the thermal bonding and pleating, Alternatively, thermal bonding or pleating may be performed, and the heat treatment may be performed after processing into a filter unit.

  In this invention, the temperature which heat-bonds the fiber web comprised from the long fiber which has a polyphenylene sulfide as a main component is 200-280 degreeC.

  In the present invention, the thermal bonding treatment refers to a treatment aimed at fusing and integrating fibers together in order to impart mechanical strength for practical use. It does not indicate temporary temporary heat bonding for the purpose of process passability. For this reason, the thermal bonding temperature when thermally bonding to the fiber web composed of the long fibers mainly composed of PPS of the present invention is 200 ° C. or higher, more preferably 250 ° C. or higher, and further preferably 260 ° C. or higher. It is necessary to be. By setting the heat bonding treatment temperature to 200 ° C. or higher, fibers can be bonded and integrated, and mechanical strength that can withstand practical use can be imparted. On the other hand, when the thermal bonding temperature is 280 ° C. or lower, the nonwoven fabric can be prevented from melting and can be stably processed.

  Examples of the method of thermal bonding in the present invention include a heat embossing roll in which engraving is performed on a pair of upper and lower roll surfaces, a roll in which one roll surface is flat (smooth), and a surface in which the other roll is engraved. Apply heat-bonding with various heating rolls, such as a hot embossing roll consisting of a combination of rolls, a thermal calender roll consisting of a pair of upper and lower flat (smooth) rolls, and an air-through method that allows hot air to pass through the nonwoven web in the thickness direction. Can do. Among them, a method of thermal bonding treatment using an embossing roll on at least one side is preferably employed because it can achieve a bulky structure excellent in air permeability and rigidity while exhibiting mechanical strength.

  Moreover, it is preferable that the linear pressure when an embossing roll is used for the heat bonding treatment is in the range of 20 to 150 kg / cm. By carrying out the linear pressure within the above range, it becomes easy to obtain a nonwoven fabric with less peeling and fluffing.

  Moreover, it is preferable that the crimping | compression-bonding area rate when using an embossing roll for a heat bonding process is 8 to 40%. By setting the pressure-bonded area ratio to 8% or more, more preferably 10% or more, and still more preferably 12% or more, mechanical strength that can be practically used can be obtained. Further, by setting the pressure-bonding area ratio to 40% or less, more preferably 30% or less, and still more preferably 20% or less, it is possible to prevent the film from being entirely formed and the air permeability from being significantly reduced.

  In the present invention, the heat treatment is performed after the heat bonding treatment. Examples of the heat treatment method include a method using a pin tenter, a clip tenter, and a net conveyor type hot air dryer if the long fiber nonwoven fabric is a sheet. In addition, if the long-fiber nonwoven fabric is after pleating, a method of putting it in a folded state between the upper and lower hot plates or a method of putting it in a net conveyor type hot air dryer can be mentioned. Further, after the long fiber nonwoven fabric is processed into a filter unit, various heat treatment methods such as a method of charging the unit into a box-type hot air dryer or the like can be employed.

The above heat treatment of the present invention, Ru is carried out in a temperature range of 250 to 280 ° C.. By setting the temperature of the heat treatment to 250 ° C. or higher, the crystallinity of the nonwoven fabric can be improved, and the sagging length at 170 ° C. can be set to 35 mm or less. Further, by setting the temperature of the heat treatment to 280 ° C. or less, the heat treatment can be performed at a temperature lower than the melting point of the PPS resin, and the PPS long fiber nonwoven fabric can be stably processed without melting.

Further, the heat treatment time of the present invention, Ru der least 1 minute. With a heat treatment time of less than 1 minute, it is difficult to increase the crystallinity before obtaining the effects of the present invention. The upper limit of the heat treatment time shall be the following 24 hours in consideration of productivity.

  In the present invention, the heat treatment after the heat bonding treatment as described above suppresses the decrease in rigidity at a high temperature and can maintain the pleat form as a mechanism. The long-fiber nonwoven fabric is excellent in dimensional stability against heat and has sufficient crystallinity for practical use. In the present invention, the long-fiber nonwoven fabric having sufficient crystallinity is further subjected to heat treatment to promote the increase in crystal size and crystallization of the amorphous portion, and the nonwoven fabric having a more stable crystal structure and By doing so, it is assumed that it is difficult to soften even at high temperatures. In addition, since the heat treatment in the present invention is carried out for the purpose of enhancing crystallinity, it is intended to remove moisture in the nonwoven fabric structure, or the nonwoven fabric is impregnated with a thermosetting resin. It is preferable that the resin is not accompanied by a cure intended to react.

The long-fiber nonwoven fabric for heat-resistant filter obtained by the present invention is, for example, an exhaust gas dust filter for coal boilers, an exhaust gas dust filter for metal blast furnaces, an exhaust gas dust filter for refuse incinerators, or an exhaust gas dust filter for diesel vehicles Preferably used.

Next, specifically described manufacturing method of the heat-resistant filter for long fibers nonwoven fabrics of the present invention from Examples, the present invention is not limited to these examples. Each characteristic value in the examples is measured by the following method.

(1) Melt flow rate (MFR) (g / 10 min)
The MFR of PPS was measured under the conditions of a measurement temperature of 315.5 ° C. and a measurement load of 5 kg according to ASTM D1238-70.

(2) Average single fiber fineness (dtex)
After pulling with an ejector and stretching, 10 small sample pieces are randomly collected from the fiber web collected on the net, and a surface photograph of 500 to 1000 times is taken with a microscope, and 10 pieces from each sample are measured. The average value was calculated by measuring the width of 100 fibers. The average width of single fibers is regarded as the average diameter of fibers having a round cross-sectional shape, and the weight per 10,000 m in length is taken as the average single fiber fineness from the solid density of the resin used, rounded off to the second decimal place. And calculated.

(3) Spinning speed (m / min)
From the average single fiber fineness (dtex) of the fiber and the discharge amount of the resin discharged from the spinneret single hole set under each condition (hereinafter abbreviated as single hole discharge amount) (g / min), based on the following formula: The spinning speed was calculated.
Spinning speed = (10000 × single hole discharge amount) / average single fiber fineness (4) Fabric weight of nonwoven fabric (g / m ² )
Measured according to JIS L1906 (2000) 5.2 mass per unit area.

(5) Sagging length test (mm)
According to the method described in [Mode for Carrying Out the Invention], the sagging length of the nonwoven fabric in the vertical direction (machine traveling direction) at room temperature (20 ° C.) and the sagging length at room temperature (20 ° C.) and 170 ° C. The difference in length was determined.

(6) Heat-resistant exposure test Using a hot air oven (TABEI SAFETY OPEN SHPS-222, manufactured by ESPEC), a required number of samples having a length of 30 cm and a width of 2 cm were introduced in the vertical direction (machine traveling direction) of the nonwoven fabric, , 210 ° C. × 1500 hours and an air circulation rate of 300 L / min.

(7) Tensile strength (N / 5cm) of nonwoven fabric and tensile strength retention (%)
The sample before and after the heat resistance exposure test of (6) above was measured at n = 3 according to JIS L1906 (2000) 5.3 tensile strength and elongation (standard time), and the average value was taken as the tensile strength. Was used to calculate the tensile strength retention.
Tensile strength retention ratio = tensile strength after heat-resistant exposure test / tensile strength before heat-resistant exposure test × 100.

Example 1
A linear polyphenylene sulfide resin (manufactured by Toray, product number: E2280) having an MFR of 160 g / 10 min was dried at a temperature of 160 ° C. for 10 hours in a nitrogen atmosphere. This linear polyphenylene sulfide resin is melted with an extruder, spun at a spinning temperature of 325 ° C., and spun at a single hole discharge rate of 1.38 g / min from a rectangular spinner with a hole diameter of 0.30 mm, and discharged in an atmosphere at a room temperature of 20 ° C. Using a rectangular ejector arranged 550 mm directly below the spinneret, the drawn yarn was pulled at an ejector pressure of 0.25 MPa, drawn, and collected on a moving net to obtain a fiber web. The average single fiber fineness of the obtained long fibers was 2.4 dtex, and the converted spinning speed was 5,726 m / min.

Subsequently, the upper roll installed on the in-line is made of a metal and a pair of upper and lower embossed rolls made of a metal flat roll and the lower roll is made of an embossed roll having a crimp area ratio of 12% engraved with a polka dot pattern. , Thermocompression-bonded at a linear pressure of 1000 N / cm and a temperature of 270 ° C. (heat-bonded), and further fed into a net conveyor type hot air dryer set at 270 ° C. and subjected to heat treatment for 20 minutes, with a basis weight of 266 g / m ² long fiber nonwoven fabrics were produced.

  This long fiber nonwoven fabric is bent by a rotary pleating machine, pleated to a pitch of 3 cm and a peak height of 5 cm, fixed to an iron frame, and hot air at a temperature of 170 ° C. is passed at a filtration air velocity of 3 m / s. However, no deformation was observed in the triangular shape of the pleat cross section. Various evaluation results are shown in Table 1.

(Example 2)
In Example 1, the long-fiber nonwoven fabric produced in the same manner as in Example 1 except that the moving net speed was changed and the basis weight was 160 g / m ² was bent by a rotary pleating machine, and the pitch was 3 cm. When the pleats were processed to a height of 5 cm and fixed to an iron frame, hot air at 170 ° C. was passed at a filtration air velocity of 3 m / s, and no deformation was observed in the triangular shape of the pleat cross section. Various evaluation results are shown in Table 1.

(Example 3)
In Example 1, except that the thermocompression bonding temperature was set to 260 ° C., the long fiber nonwoven fabric produced in the same manner as in Example 1 was bent with a rotary pleating machine so that the pitch was 3 cm and the peak height was 5 cm. It was processed, fixed to an iron frame, and warm air at 170 ° C. was passed at a filtration air velocity of 3 m / s, and no deformation was observed in the triangular shape of the pleat cross section. Various evaluation results are shown in Table 1.

Example 4
In Example 1, except that the heat treatment conditions were set to a temperature of 280 ° C. and a time of 10 minutes, the long-fiber nonwoven fabric produced in the same manner as in Example 1 was bent with a rotary pleating machine, and the pitch was 3 cm and the height was 5 cm. When pleating was performed and fixing to an iron frame and hot air at 170 ° C. was passed at a filtration air velocity of 3 m / s, no deformation was seen in the triangular shape of the pleated cross section. Various evaluation results are shown in Table 1.

(Example 5)
The long-fiber nonwoven fabric produced in the same manner as in Example 1 was impregnated with a water-dispersed phenol resin (manufactured by DIC, TD4304) with a dip mangle, and dried and cured at a temperature of 250 ° C. for 4 minutes using a pin tenter. . The fixing ratio of the water-dispersible phenol resin was 25% by mass with respect to the total weight of the nonwoven fabric.

  This long fiber nonwoven fabric is bent by a rotary pleating machine, pleated to a pitch of 3 cm and a peak height of 5 cm, fixed to an iron frame, and hot air at a temperature of 170 ° C. is passed at a filtration air velocity of 3 m / s. However, no deformation was observed in the triangular shape of the pleat cross section. Various evaluation results are shown in Table 1.

(Comparative Example 1)
The long fiber nonwoven fabric produced in the same manner as in Example 1 except that the heat treatment for 20 minutes by the net conveyor type hot air dryer set at a temperature of 270 ° C. was not performed in Example 1. Folded with a machine, pleated to a pitch of 3 cm, and a mountain height of 5 cm, fixed to an iron frame, and warm air at 170 ° C. was passed at a filtration air speed of 3 m / s, resulting in a large deformation in the triangular shape of the pleated cross section It was seen. Various evaluation results are shown in Table 1.

  Example 1 in which heat treatment is performed after heat bonding and the sag length at normal temperature (20 ° C.) is 9 mm, and the difference in sag length between normal temperature (20 ° C.) and 170 ° C. is 23 mm, Even when ventilated, no change was observed in the pleated form retention, and the tensile strength retention was 90% or more, and the heat resistance was excellent. Example 2 in which a phenolic resin is fixed to a long-fiber nonwoven fabric, the sagging length at room temperature (20 ° C.) is 12 mm, and the sagging length difference between the room temperature (20 ° C.) and 170 ° C. is 21 mm. Even when warm air was passed, no change was observed in the pleat form retention, but the tensile strength retention decreased to 36%.

  On the other hand, Comparative Example 1 in which heat treatment was not performed after heat bonding was excellent in that the tensile strength retention rate was 90% or more, but the difference in sagging length between room temperature (20 ° C.) and 170 ° C. was 49 mm. A large change was observed in pleat form retention when warm air was passed.

1: Measurement piece 2: One end of the measurement piece 3: Measurement piece placement block 4: Measurement piece after 1 hour

Claims (1)

A fiber web composed of long fibers mainly composed of polyphenylene sulfide is heat-bonded at a temperature of 200 to 280 ° C., and then heat-treated at a temperature of 250 to 280 ° C. and a time of 1 minute to 24 hours. A method for producing a long-fiber non-woven fabric for heat-resistant filters.

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