JP2020196963A - Melt-blown nonwoven fabric, heat-resistant filter laminate, and manufacturing method thereof - Google Patents

Abstract

To provide a melt-blown nonwoven fabric which enables a filter material made of nonwoven fabric for filter excellent in collection performance, with high air permeability and low pressure loss, capable of extending service life to be provided, a nonwoven fabric for use in melt-flow nonwoven fabric and a heat-resistant filter thereof, a heat-resistant filter laminate, and a manufacturing method thereof.SOLUTION: A melt-blown nonwoven fabric of the present invention is mainly composed of a thermoplastic resin. The melt-blown nonwoven fabric has a mode of fiber diameter of 1 μm or less, and an abundance of fiber having a size of 6.0 μm or more of 5% or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a melt-blown non-woven fabric and a heat-resistant filter laminate, which have a higher air permeability than the conventional one and are excellent in filtration performance, and a method for producing them.

In recent years, environmental awareness has been increasing in countries with remarkable economic growth such as the People's Republic of China. One example is the environmental policy for the increase of PM2.5, which is the dust emitted from coal boilers and the like. This policy requires that strict emission standards be achieved, and against the background of these environmental regulations, a filter that has heat resistance and higher filtration performance is required.

High filtration performance is a non-woven fabric that has high dust collection properties and low pressure loss even during long-term use. Melt blown non-woven fabrics may be used as such filters to solve the problem. For example, the dust collecting layer is a melt-blown non-woven fabric made of polyphenylene sulfide, and the non-woven fabric, felt, woven fabric or knitting made of heat-resistant fibers is used as a strength-retaining layer, and the filter cloth for a bag filter is laminated by the water flow entanglement method. Has been proposed (see Patent Document 1).

Further, for the purpose of further improving the pressure loss of melt blow, a non-woven fabric sheet using a melt blow non-woven fabric composed of different fiber groups as a filter medium has been proposed by using bases having different pore diameters (see Patent Document 2).

Certainly, according to these proposals, it is possible to obtain a bag filter filter cloth having better filtration performance than before.

International Publication No. 2017/0886186 Japanese Unexamined Patent Publication No. 2006-37295

However, in Patent Document 1 described above, laminating processing is performed by entanglement, and there is a concern that dust may leak from the entangled portion and the filtration performance may deteriorate. Furthermore, since the dust collecting layer, which is a melt-blown non-woven fabric, has not been heat-treated, it has sufficient filtration performance, such as tearing during backwashing and significant heat shrinkage when used in an environment of 90 ° C or higher. There is a problem that it cannot be demonstrated. Further, Patent Document 2 assumes polyolefin and is inferior in heat resistance when used at a high temperature. Further, when the fiber diameter configuration of the present patent is used, the pressure loss is improved, but there is a problem that the ratio of the dense fiber layer is small and sufficient dust collection performance cannot be obtained.

Therefore, an object of the present invention has been made in view of the above circumstances, and a melt-blown nonwoven fabric and a heat-resistant filter laminate having the same collection performance as the conventional one and suppressing the reduction of pressure loss of the melt-blown nonwoven fabric. To provide and to provide a method of manufacturing them.

As a result of diligent studies to achieve the above object, the present inventors have made it possible to control the fiber diameter by producing the melt-blown non-woven fabric under specific conditions, resulting in high dust collection performance and low pressure loss. We have found that a compatible non-woven fabric can be obtained.

The present invention has been completed based on these findings, and the following inventions are provided according to the present invention.

The melt-blow non-woven fabric of the present invention is a melt-blow non-woven fabric composed of fibers containing a thermoplastic resin composition as a main component, and the mode of the single fiber diameter of the fibers is 1 μm, and the presence of fibers of 6.0 μm or more. The rate is 5% or more.

Further, it is a heat-resistant filter laminated body in which at least one layer made of the melt-blown non-woven fabric and a base cloth are bonded.

Further, it is a method for producing the melt-blown nonwoven fabric, in which the following steps (1) to (3) are sequentially performed.
Step (1): From the spinneret satisfying the following condition (i), the single-hole discharge rate of the thermoplastic resin composition is 0.20 g / (minutes / holes) or more and 1.10 g / (minutes / holes) or less. The process of spinning in a range to form threads.

Condition (i): A step (2): which has discharge holes (a) and discharge holes (b) having different hole diameters, and these are arranged alternately or regularly in a straight line in the width direction of the spinneret. When the melting point of the thermoplastic resin composition is Tm, a gas heated to (Tm + 10 ° C.) or higher (Tm + 50 ° C.) or lower and pressurized to 0.10 MPa or higher and 1.00 MPa or lower is applied to the threads. The process of spraying.
Step (3): A step of depositing the fibers on the collector.

Further, it is a method for producing a heat-resistant filter laminate having a step of adhering at least one base cloth selected from the group consisting of non-woven fabric, felt, woven fabric, and knitted fabric to the melt-blown non-woven fabric.

According to the present invention, it is possible to provide a filter medium made of a non-woven fabric for a filter, which has excellent collection performance, a high air volume, a low pressure loss, and a long life, and is suitably used for industrial applications such as filters.

It is a single fiber diameter distribution according to the present invention. It is a single fiber diameter distribution regarding a melt blown nonwoven fabric consisting of a single pore. It is a single fiber diameter distribution relating to a non-woven fabric made of a base having different pore diameters.

The melt-blow non-woven fabric of the present invention is a melt-blow non-woven fabric containing a thermoplastic resin as a main component, has a fiber diameter mode of 1 μm or less, and has a fiber abundance rate of 6.0 μm or more of 5% or more. The details will be described below.

(Thermoplastic resin)
The main components of the thermoplastic resin of the melt blown non-woven fabric of the present invention include, for example, polyphenylene sulfide, polyetherimide, polyethersulfone, polysulfone, polyphenylene ether, polyester, polyarylate, polyamide, polyamideimide, polycarbonate, polyolefin, and polyether. A thermoplastic resin such as ether ketone and a thermoplastic resin obtained by copolymerizing these are preferable.

Among these, thermoplastic resins containing polyphenylene sulfide resin and polyester resin as main components have excellent fiber spinnability, while melt-blown non-woven fabric after fabrication has a problem of low thermal dimensional stability. This is an example of a preferable embodiment in which thermal dimensional stability can be imparted by using the method for producing a melt-blown nonwoven fabric of the present invention, and it can be used at a high temperature. In particular, a thermoplastic resin containing a polyphenylene sulfide resin and a polyester resin as main components is preferable. Further, a thermoplastic resin obtained by copolymerizing these can also be preferably used. Here, these may be referred to as polyester resin or polyphenylene sulfide resin.

Further, in the present invention, "as a main component" means "a case where the component is contained in an amount of 85% by mass or more and is composed of only the component".

Therefore, the above-mentioned thermoplastic resin has a crystal nucleating agent, a matting agent, a pigment, a fungicide, an antibacterial agent, a flame retardant, and a light stabilizer according to desired characteristics within the range in which the effect of the present invention is exhibited. , UV absorbers, antioxidants, fillers, lubricants, hydrophilic agents and the like can be added.

The thermoplastic resin, which is the main component of the fibers constituting the melt-blown non-woven fabric of the present invention, has an MFR of 100 g / 10 minutes measured according to ASTM D1238-70 (measurement load 5 kg weight) at a temperature of melting point + 34.5 ° C. A preferred embodiment is 2000 g / 10 minutes or less. By setting the MFR to 100 g / 10 minutes or more, more preferably 150 g / 10 minutes or more, good fluidity can be obtained and the fibers can be easily thinned into fibers. On the other hand, when the MFR is 2000 g / 10 minutes or less, more preferably 1500 g / 10 minutes or less, the back pressure of the mouthpiece is appropriately maintained and the spinning stability is excellent.

The thermoplastic resin, which is the main component of the fibers constituting the melt-blown nonwoven fabric of the present invention, preferably has a weight average molecular weight of 10,000 or more and 75,000 or less as measured by gel permeation chromatography (GPC). By setting the weight average molecular weight to 10,000 or more, more preferably 20,000 or more, the spinnability is improved without causing yarn breakage. On the other hand, by setting the weight average molecular weight to 75,000 or less, more preferably 60,000 or less, still more preferably 50,000 or less, the spun polymer can be sufficiently stretched with hot air during the production of melt-blown non-woven fabric, and a fine fiber layer can be formed. To do.

On the other hand, by setting the MFR to 2000 g / 10 minutes or less, more preferably 1500 g / 10 minutes or less, the back pressure of the mouthpiece is appropriately maintained and the spinning stability is excellent.

(Melt blow non-woven fabric and fabric making process)
In the production method of the present invention, it is important to have a fabric-making step of forming a melt-blown nonwoven fabric made of fibers containing the above-mentioned thermoplastic resin as a main component. The melt-blown non-woven fabric is produced by spraying heated compressed air onto the yarn spun from the spinneret, thinning the fibers, self-fusing them, and depositing the discharged fibers on a collector. Since it is thinned by being blown with compressed air, it is a non-woven fabric with a variation in fiber diameter distribution compared to long-fiber non-woven fabrics such as spunbond and flash spinning. That is, since the fibers are contained with a certain variation from those having a small fiber diameter to those having a large fiber diameter, when the fibers have the same pores, the fiber diameter distribution is generally monomodal. On the other hand, the melt-blown non-woven fabric of the present invention has a fiber diameter distribution of at least two peaks or more by spinning from a mouthpiece having two or more types of pore diameters and the two or more types of pores arranged alternately or regularly. By being composed of a fine fiber group and a thick fiber group, it is possible to obtain a non-woven fabric having a higher air permeability and a lower pressure than the conventional one. Further, it is preferable that the mouthpieces having two or more kinds of hole diameters are regularly arranged one by one alternately from the viewpoint of being able to be uniformly stretched. When there are a large hole and a small hole, the diameter of the small hole is preferably 0.1 mm or more and 0.5 mm or less, and the diameter of the large hole is 0.3 mm or more and 1.0 mm or less. Therefore, a non-woven fabric having excellent spinnability and a desired fiber diameter can be obtained. The distance between the base holes is preferably a constant interval. By doing so, the fibers can be uniformly drawn and can be spun without coalescing with adjacent fibers. The interpupillary distance shown here is the distance from the center of the hole to the center of the adjacent hole.

In general, examples of the non-woven fabric form other than the melt-blown non-woven fabric include spunbonded non-woven fabric, flash-spun non-woven fabric, wet non-woven fabric, card non-woven fabric and air-laid non-woven fabric, but spunbond non-woven fabric, card non-woven fabric and air-laid non-woven fabric have fiber diameters. Since it is thick and has poor texture uniformity, the surface roughness tends to be large. Further, since the flash-spun non-woven fabric has a high density, the air flow rate tends to decrease and the pressure loss tends to improve.

In the melt-blown nonwoven fabric of the present invention, it is important that the mode of the single fiber diameter of the fibers constituting the melt-blown nonwoven fabric is 1 μm or less. As a result, dense fibers are formed in the non-woven fabric, resulting in a melt-blown non-woven fabric having excellent filtration performance. Further, the mode of the single fiber diameter in the present invention indicates the mode of the single fiber diameter, measures the single fiber diameter constituting the non-woven fabric, and divides the single fiber diameter between integers (less than 1 μm, 1 or more and less than 2 μm, The most measured section when 2 or more and less than 3 μm, 3 or more and less than 4 μm, etc.) is defined as the section with the highest abundance rate from the population. The melt-blown nonwoven fabric of the present invention has the highest abundance of single fiber diameters in the range of 0 μm or more and 1 μm or less. Furthermore, the preferred abundance of modes in the present invention is 10% or more, more preferably 20% or more, still more preferably 30% or more. Here, the abundance rate is the abundance rate of "number".

It is important that the single fiber diameter of the melt-blown nonwoven fabric of the present invention is 6.0 μm or more and the abundance of fibers is 5% or more. Due to the presence of these fibers, the air flow rate is moderately improved, and a non-woven fabric having a lower pressure loss than the conventional product can be obtained. The abundance of fibers of 6.0 μm or more is preferably 5% or more, more preferably 15% or more, still more preferably 30% or more, and the upper limit is preferably 50% or less, more preferably 45% or less, and further. It is preferably 40% or less. This makes it possible to prevent dust from flowing into the non-woven fabric and impairing the deterioration of filterability. Here, the method of obtaining the abundance rate is the same as the method of obtaining the mode of the single fiber diameter.

The number average single fiber diameter of the melt-blown non-woven fabric of the present invention is preferably 0.1 μm or more and 5.0 μm or less. By setting the number average single fiber diameter to preferably 5.0 μm or less, more preferably 4.5 μm or less, still more preferably 4.0 μm or less, the uniformity of the basis weight of the melt blow nonwoven fabric is improved, and the melt blow is excellent in collection efficiency. A non-woven fabric can be obtained. On the other hand, by setting the number average single fiber diameter to preferably 0.1 μm or more, more preferably 0.5 μm or more, still more preferably 1.0 μm or more, the fibers are formed when the polymer is stretched and thinned in the manufacturing process. It is possible to suppress the generation of shots (polymer lumps) by cutting, and it is possible to prevent an increase in pressure loss when used as a filter filter medium.

The thickness of the melt-blown nonwoven fabric is preferably 2.0 mm or less, more preferably 1.5 mm or less. By setting the thickness in this way, it is possible to prevent a decrease in the air flow rate of the melt blow nonwoven fabric and maintain sufficient filtration performance.

In order to obtain the above-mentioned number average single fiber diameter, mode, and fiber abundance of 6.0 μm or more, it is necessary to appropriately adjust the raw material viscosity, the mouthpiece, the mouthpiece hole discharge rate, and the hot air pressure at the time of manufacturing the melt blown nonwoven fabric.

The measurement of the single fiber diameter is the measurement of the melt blown non-woven fabric part, but the part where the fiber shape is partially deformed or cannot be confirmed due to thermocompression bonding or welding is excluded, and the single fiber diameter can be confirmed. Measurements shall be carried out.

In the method for producing a melt-blown nonwoven fabric of the present invention, it is preferable to carry out the following steps (1) to (3) in order.
Step (1): From the spinneret satisfying the following condition (i), the single-hole discharge rate of the thermoplastic resin composition is 0.20 g / (minutes / holes) or more and 1.10 g / (minutes / holes) or less. The process of spinning in a range to form threads.

Condition (i): A step (2): which has discharge holes (a) and discharge holes (b) having different hole diameters, and these are arranged alternately or regularly in a straight line in the width direction of the spinneret. When the melting point of the thermoplastic resin composition is Tm, a gas heated to (Tm + 10 ° C.) or higher (Tm + 50 ° C.) or lower and pressurized to 0.10 MPa or higher and 1.00 MPa or lower is applied to the threads. The process of spraying.
Step (3): A step of depositing the fibers on the collector.

The speed of the mouthpiece discharge hole for obtaining the melt-blown non-woven fabric of the present invention is preferably 0.20 g / (minutes / holes) or more, more preferably 0.32 g / (minutes / holes) or more, and further preferably 0. It is 42 g / (minute / hole) or more. As a result, a melt-blown non-woven fabric having excellent spinnability can be obtained. On the other hand, preferably 1.10 g / (minutes / holes) or less, more preferably 0.85 g / (minutes / holes) or less, and further preferably 0.70 g / (minutes / holes) or less is sufficient. It is possible to maintain a good dust collection performance. Further, the mouthpiece hole discharge rate described here indicates a value obtained by dividing the discharge amount of all the holes by the hole area of all the mouthpieces.

The preferred hot air pressure for obtaining the melt-blown nonwoven fabric of the present invention is preferably 0.10 MPa or more, more preferably 0.15 MPa or more, still more preferably 0.20 MPa or more. This makes it possible to refine the sufficiently spun thermoplastic resin. On the other hand, it is preferably 1.00 MPa or less, more preferably 0.90 MPa or less, and further preferably 0.80 MPa or less, so that sufficient dust collection performance can be maintained.

According to the method for producing a melt-blown non-woven fabric of the present invention, the texture of the melt-blown non-woven fabric is preferably 10 g / m ² or more, more preferably 10 g / m ² or more, in order to maintain practical mechanical strength and sufficient filtration performance. Is 20 g / m ² or more. On the other hand, the basis weight is more preferably 400 g / m ² or less, and further preferably 200 g / m ² or less, so that a decrease in the air volume can be prevented and sufficient filtration performance can be maintained.

In the fabric-making process according to the present invention, the temperature of the extruder for melting the resin and the spinneret is preferably (melting point + 10 ° C. of the resin used) or more (melting point + 50 ° C.) or less. Within this range, solidification of the resin, low fluidization, or deterioration of the resin due to high temperature can be prevented.

Further, in the cloth making process according to the present invention, the temperature of the heating high-speed gas is set to be 0 ° C. or more higher than the spinning temperature, so that the fibers can be efficiently thinned and can withstand practical use by self-fusion between the fibers. A strong melt blown non-woven fabric can be obtained. Further, by setting the temperature of the heating high-speed gas to 30 ° C. or lower, more preferably 25 ° C. or lower, and further preferably 20 ° C. or lower than the spinning temperature, the generation of shots (polymer lumps) is suppressed and the non-woven fabric is used. Can be stably manufactured.

The apparent density of the melt-blown nonwoven fabric of the present invention is preferably 0.10 g / cm ³ or more and 0.70 g / cm ³ or less. By setting the apparent density to 0.70 g / cm ³ or less, preferably 0.60 g / cm ³ or less, more preferably 0.50 g / cm ³ or less, when used as a filter filter medium, the filtration performance is improved. It becomes a melt blown non-woven fabric that does not decrease. On the other hand, by setting the apparent density to 0.10 g / cm ³ or more, preferably 0.12 g / cm ³ or more, and more preferably 0.15 g / cm ³ or less, high density is suppressed and the pressure loss is low. ..

The air permeability of the melt-blown non-woven fabric of the present invention is preferably 20 cm ³ / (cm ² · sec) or more and 120 cm ³ / (cm ² · sec) or less. It was used as a filter filter medium by setting the air permeability to 120 cm ³ / (cm ² · sec) or less, preferably 100 cm ³ / (cm ² · sec) or less, and more preferably 80 cm ³ / (cm ² · sec) or less. At that time, the melt-blown non-woven fabric does not deteriorate the filtration performance. On the other hand, by setting the air volume to 20 cm ³ / (cm ² · sec) or more, preferably 40 cm ³ / (cm ² · sec) or more, and more preferably 50 cm ³ / (cm ² · sec) or more, the melt blown non-woven fabric can be used. The densification is suppressed and the pressure loss is low.

(Heat treatment process and laminating process)
Subsequently, the manufacturing method of the heat treatment step and the laminating step in the present invention will be described.

(1) Heat treatment step In the heat treatment step, a method of heat-bonding with a calendar roll and processing can be mentioned. From the viewpoint of suppressing a decrease in air flow due to high density, a hot air heat treatment method in which a sheet is gripped and heat treated with hot air or a surface temperature is cooled It is preferable to perform the heat treatment using a belt press device that heat-treats between two sets of flexible belts having a crystallization temperature of −3 ° C. or higher and a melting point of −3 ° C. or lower. Further, as long as the sheet can be gripped by other treatment methods and can be carried out at the above temperature, it is sufficient if it is possible to suppress the heat shrinkage that occurs above the softening point.

In the heat treatment step according to the present invention, the contact time between the belt conveyor and the melt-blow non-woven fabric is appropriately adjusted according to the type of thermoplastic resin of the fibers constituting the melt-blow non-woven fabric and the texture and thickness of the non-woven fabric. However, the contact time is preferably at least 3 seconds or more, more preferably 5 seconds or more, and further preferably 10 seconds or more. By setting the contact time in this way, the melt-blown nonwoven fabric can be sufficiently heat-treated to impart excellent thermal dimensional stability.

The transport speed of the melt-blown non-woven fabric during heat treatment is preferably 10.0 m / min or less, more preferably 8.0 m / min or less, still more preferably 6.0 m / min or less, so that thermal crystallization of the fibers proceeds. It is possible to prevent the melt-blown non-woven fabric from being softened by rapid heating before the heat treatment, causing the thickness to be crushed and the fibers being fused to each other to form a film.

Further, the heat treatment process may be carried out before the bonding with the base cloth or after the bonding.

The KES surface roughness of the melt-blown non-woven fabric after bonding is not particularly determined, but by setting it to 1.60 μm or less, preferably 1.40 μm or less, and more preferably 1.20 μm or less, dust can be obtained from the filtered non-woven fabric. A dust layer is formed on the surface layer without being mixed in the voids, and stable filtration performance can be obtained for a long period of time.

The melt-blown non-woven fabric of the heat-resistant filter laminate of the present invention was subjected to a fluffing test measured according to 9.2 “Friction tester type II (Gakushin type) method” of JIS L0849: 2013 “Dyeing fastness test method for friction”. The surface of the non-woven fabric is rubbed back and forth 500 times with a friction element to which a white cotton cloth for friction is attached, and the surface condition of the test piece before and after the test is visually observed and fluffiness is 5 when observed using a scanning electron microscope (SEM). (Indistinct visually) is preferable. As a result, a non-woven fabric that prevents dust from entering the filtration surface layer and has excellent wiping property is obtained.

The apparent density of the non-woven fabric used in the heat-resistant filter laminate of the present invention is 0.40 g / cm ³ or less, preferably 0.38 g / cm ³ or less, and more preferably 0.35 g / cm ³ or less. It is possible to extend the life of the filter by suppressing the decrease in pressure and reducing the pressure loss. On the other hand, by setting the apparent density to 0.10 g / cm ³ or more, preferably 0.12 g / cm ³ or more, more preferably 0.14 g / cm ³ or more, the strength is reduced due to the reduction of the bonding points between the fibers. It can be a non-woven fabric having strength and handleability that can be suppressed and can withstand practical use.

Further, the dry heat shrinkage rate of the non-woven fabric used for the heat-resistant filter laminate of the present invention at a temperature of 200 ° C. is preferably 2% or less, more preferably 1% or less. By doing so, it is possible to obtain a non-woven fabric in which there is no dimensional change or structural change inside the non-woven fabric during use even in a high temperature environment. In addition, the non-woven fabric may stretch due to tension relaxation due to heating, etc., and similarly to the above, the dry heat shrinkage rate is preferably -2% or more in order to prevent dimensional changes and structural changes inside the non-woven fabric during use in a high temperature environment. , More preferably -1% or more, and the dry heat shrinkage rate is close to 0%.

(2) Laminating Step In the method for producing a heat-resistant filter laminate of the present invention, the melt-blown non-woven fabric obtained from the cloth-making step is further subjected to the polyphenylene sulfide, metaaramid, polyimide, fluororesin and glass before and after the heat-treating step. It is important to bond the base fabric, which is a non-woven fabric, felt, woven fabric, or knitted fabric containing at least one as a main component, to the melt-blown non-woven fabric. By doing so, the melt blow layer becomes an excellent filter medium, and the base fabric has sufficient strength and durability to become an excellent heat-resistant filter laminate. The non-woven fabric, felt, woven fabric, or knitted fabric is not particularly specified, but it is preferably made of the same resin as the melt-blown non-woven fabric in order to improve the adhesiveness.

In general, the method of joining the non-woven fabric and other fabrics includes bonding by thermocompression bonding and entanglement treatment by needle punching or water flow entanglement. However, in the bonding step according to the present invention, the formation of a dense layer is suppressed. In order to prevent the filtration performance from being deteriorated due to the generation of voids in the non-woven fabric due to entanglement, a method in which the base fabric is melted by a flame melting method such as frame laminating and bonded to the melt blow non-woven fabric is more preferable.

As the base fabric according to the present invention, a non-woven fabric, felt, woven fabric, or knitting containing at least one of polyphenylene sulfide, metaaramid, polyimide, fluororesin, and glass as a main component is preferable. By doing so, a heat-resistant filter laminate that can withstand high temperatures can be obtained.

By setting the basis weight of the base cloth to 200 g / m ² or more, preferably 250 g / m ² or more, and more preferably 300 g / m ² or more, the strength is sufficient to withstand handling and processing.

Since the heat-resistant filter laminate of the present invention is excellent in extending the life of the filtration performance, it can be suitably used for industrial applications such as filters. In addition, it can be suitably used for filters such as coal boilers and waste incineration waste filters, which require heat resistance and chemical resistance and higher filtration performance.

Next, the method for producing the melt-blown nonwoven fabric of the present invention and the heat-resistant filter laminate will be specifically described based on Examples. The present invention is not limited to these examples.

[Measuring method]
(1) Melt flow rate (MFR) (g / 10 minutes):
The MFR of the polyphenylene sulfide resin was measured three times under the conditions of a measurement temperature of 315.5 ° C. and a measurement load of 5 kg according to ASTM D1238-70, and the average value was taken as the MFR.

(2) Intrinsic viscosity (IV):
The intrinsic viscosity IV of the polyethylene terephthalate resin was measured three times by the following method, and the average value was taken. 8 g of the sample was dissolved in 100 ml of orthochlorophenol, and the relative viscosity ηr 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 )
Here, η is the viscosity of the polymer solution, η ₀ is the viscosity of orthochlorophenol, t is the falling time of the solution (seconds), d is the density of the solution (g / cm ³ ), and t ₀ is the falling time of orthochlorophenol. (Seconds) and d ₀ represent the density of orthochlorophenol (g / cm ³ ), respectively.
Next, the intrinsic viscosity IV was calculated from the above relative viscosity η _r by the following formula.
-IV = 0.0242η _r +0.2634.

(3) Melting point (° C):
The melting point of the thermoplastic resin used was measured three times using a differential scanning calorimeter (Q100 manufactured by TA Instruments) under the following conditions, and the average value of the endothermic peak apex temperature was calculated to obtain the melting point of the measurement target. did. When there are a plurality of endothermic peaks in the thermoplastic resin before fiber formation, the peak peak temperature on the highest temperature side is used. Further, when the fiber is to be measured, the measurement can be performed in the same manner, and the melting point of each component can be estimated from a plurality of endothermic peaks.
・ Measurement atmosphere: Nitrogen flow (150 ml / min)
・ Temperature range: 30 to 350 ° C
・ Temperature rise rate: 20 ° C / min ・ Sample amount: 5 mg.

(4) Weight average molecular weight:
The weight average molecular weights of the thermoplastic resins and fibers used were calculated in terms of polyethylene and polymethyl methacrylate using gel permeation chromatography (GPC), which is a type of size exclusion chromatography (SEC). The measurement conditions of GPC are shown below.

<At the time of PPS measurement>
・ Equipment: Senshu Kagaku SSC-7100
-Column name: Senshu Kagaku GPC3506
・ Eluent: 1-chloronaphthalene ・ Detector: Differential refractive index detector ・ Column temperature: 210 ℃
・ Flow rate: 1.0 ml
-Sample injection amount: 300 μL.

<When measuring PP>
-Device: Polymer Laboratories PL-220
-Column name: Showa Denko Shodex HT806M
Eluent: 1,2,4-trichlorobenzene (TCB) (with 0.1% BHT added)
-Detector: Differential refractive index detector-Column temperature: 145 ° C
・ Flow rate: 1.0 ml
-Sample injection amount: 200 μL (previously, heating and stirring at 160 to 170 ° C. for about 20 minutes).

<At the time of PET measurement>
-Device: Polymer Laboratories PL-220
-Column name: Showa Denko Shodex KF-404
-Eluent: HFIP (hexafluoro-2-propanol)
・ Detector: Differential refractive index detector ・ Column temperature: 210 ℃
・ Flow rate: 1.0 ml
-Sample injection amount: 200 μL.

(5) Number average single fiber diameter (μm) and mode:
Fifty small samples were randomly collected from the melt-blown non-woven fabric collected on the belt conveyor, and surface photographs were taken with a scanning electron microscope of VE7800 manufactured by KEYENCE Co., Ltd. at a magnification of 1000 to 2000, and 10 samples were taken from each sample, for a total of 500. The width of the fibers of the book was measured and the average value was calculated. From the average width of single fibers, the second decimal place was rounded off to obtain the fiber diameter.

The single fiber diameter mode indicates the mode of the single fiber diameter, measures the single fiber diameter constituting the non-woven fabric, and divides the single fiber diameter between integers (less than 1 μm, 1 or more and less than 2 μm, 2 or more). The section with the highest abundance rate from the population was defined as the section with the highest measurement rate when the distance was less than 3 μm, 3 or more and less than 4 μm.

(6) Non-woven fabric basis weight (g / m ² ):
Based on "6.2 Mass per unit area" of JIS L1913: 2010 "General Non-woven Test Method", 3 test pieces of 20 cm x 25 cm were collected per 1 m of sample width, and each mass (g) in the standard state. ) Was weighed, and the average value was expressed as the mass per 1 m ² (g / m ² ).

(7) Thickness of non-woven fabric (μm):
According to "4.1 Thickness" of JIS L1906: 2000 "General Nonwoven Fabric Test Method", a pressurizer with a diameter of 10 mm is used, and a thickness of 10 points is applied to the nonwoven fabric and the belt conveyor at equal intervals in the width direction at a load of 10 kPa. The measurement was performed in units of 0.01 mm, and the third decimal place of the average value was rounded off.

(8) Aeration rate of non-woven fabric (cm ³ / (cm ² seconds)):
According to JIS L1913: 2010 "General non-woven fabric test method""6.8.1 Frazier type method", 10 fiber sheets cut into 15 cm squares were used with the breathability tester FX3300 manufactured by Textest Co., Ltd. The test pressure was 125 Pa. From the average value of the obtained values, the second decimal place was rounded off to obtain the air volume.

(9) Dry heat shrinkage rate (%) of non-woven fabric:
The measurement was performed according to "6.10.3 Dry heat dimensional change rate" of JIS L1913: 2010 "General non-woven fabric test method". The temperature inside the constant temperature dryer was set to 200 ° C., and heat treatment was performed for 10 minutes.

(10) Filtration performance evaluation:
The performance of the heat-resistant filter laminate was measured according to VDI3926. The measurement sample has a diameter of 150 mm, an inlet dust concentration of 5.0 ± 0.5 g / cm ³ , a filtration wind speed of 2 m / min, and when it reaches 1000 Pa, the dust on the surface of the filter medium is removed by a pulse. It was carried out 30 times + 5000 times of aging + 30 times at the end, and the circulation time, pressure loss, outlet concentration and dust collection efficiency until the end of the pulse cleaning for the last 30 times were determined by the following methods.
・ Circulation time (seconds): Time until the last 30 payments are completed (the last 3 digits are rounded off)
-Pressure loss (Pa): Pressure loss after the last 30th wiping off-Outlet dust concentration (mg / m ³ ) = Filter media penetration dust weight / (1.85 x circulation time (seconds) / 3600)
-Collection efficiency (%) = (1-outlet dust concentration / 5) x 100.

[Example 1]
(Spinning and sheeting)
A polyphenylene sulfide (PPS) resin having an MFR of 600 g / 10 min, a melting point of 281 ° C. and a weight average molecular weight of 43000 was dried at a temperature of 150 ° C. for 24 hours in a nitrogen atmosphere. This polyphenylene sulfide resin is melted by an extruder, the spinning temperature is 310 ° C., holes having a hole diameter (diameter) φ of 0.30 mm and 0.60 mm are alternately arranged, and a single hole is discharged from a spinning mouthpiece having a pitch of 1.6 mm. Spinned at an amount of 0.16 g / (min / hole) and a discharge hole speed of 0.67 g / min, and compressed air at a temperature of 340 ° C. heated by an air heater was blown at a pressure of 0.45 MPa. A melt-blown non-woven fabric having a grain size of 40 g / m ² was obtained by collecting on a moving belt conveyor at a position of 100 mm from the spinneret. The number of fibers constituting the obtained melt-blown non-woven fabric The average single fiber diameter is 3.3 μm, the mode is 1 μm, the fiber abundance of 6.0 μm or more is 20%, and the shot (polymer lump) is formed in 1 hour of spinning. No occurrence occurred, and the spinnability was good.

(Physical properties of non-woven fabric)
The thickness of the obtained melt-blown non-woven fabric was 0.22 mm, and the air flow rate was 52 cm ³ / (cm ² seconds). The results are shown in Table 1.

(Heat treatment of non-woven fabric)
It consists of a "Teflon (registered trademark)" resin belt woven with glass fiber as a core material, and two sets of belt conveyors with a belt thickness of 0.31 mm and a belt surface with a Beck smoothness of 2.6 seconds are used. They were arranged one above the other so that the clearance between them was zero. The collected melt-blown non-woven fabric was bonded to the entire surface of the non-smooth surface of the paper pattern processed by PTFE, passed between the belt conveyors, and conveyed at a speed of 2 m / min while being fully gripped, and the temperature of the upper belt surface was 140. The surface temperature of the lower paper pattern was set to 40 ° C., and the sheet was passed through a heated heat treatment zone having a length of 1 m and heat-treated for 30 seconds. The heat shrinkage of the melt-blown non-woven fabric after the dry heat treatment was 0%, and no waviness, deterioration of the formation, and surface unevenness were observed.

(Method of laminating non-woven fabric)
PPS short fibers with a number average single fiber diameter of 14.5 μm were carded and cross-wrapped, and needle punching was performed on both sides of a PPS fabric with a basis weight of 120 g / m ² and 2.2 T to obtain 550 g / m ² PPS felt. Obtained. One side of this felt was flame-processed to form a non-smooth surface of the melt-blown non-woven fabric as a bonded surface, and the bonding process was performed to obtain a laminated non-woven fabric. The obtained laminated non-woven fabric was sufficiently adhered and had good adhesiveness.

(Filtration performance evaluation)
As a result of evaluating the filtration performance using the obtained laminated non-woven fabric, the circulation time was 17,000 seconds, the pressure loss was 175 Pa, the outlet concentration was 0.05 g / m ³ , and the dust collection rate was 99.9989%.

[Example 2]
(Spinning and sheeting)
Under the same conditions as in Example 1, except that holes having a hole diameter (diameter) φ of 0.40 mm and 0.80 mm were alternately arranged and a discharge hole speed of 0.57 g / min was set using a spinneret having a pitch of 1.6 mm. Melt blow non-woven fabric was made. The number of fibers constituting the obtained melt-blown non-woven fabric has an average single fiber diameter of 3.5 μm, a mode of 1 μm, and a fiber abundance rate of 6.0 μm or more of 33%, and the shot (polymer mass) is formed by spinning for 1 hour. No occurrence occurred, and the spinnability was good.

(Physical properties of non-woven fabric)
The thickness of the obtained melt-blown non-woven fabric was 0.24 mm, and the air flow rate was 73 cm ³ / (cm ² seconds). The results are shown in Table 1.

(Heat treatment of non-woven fabric)
The same belt conveyor as in Example 1 was used, and heat treatment was performed under the same conditions. The heat shrinkage of the melt-blown non-woven fabric after the dry heat treatment was 0%, and no waviness, deterioration of the formation, and surface unevenness were observed. The results are shown in Table 1.

(Method of laminating non-woven fabric)
Under the same conditions as in Example 1, the felt and the bonding process were carried out to obtain a laminated non-woven fabric. The obtained heat-resistant filter laminate was sufficiently adhered, and the adhesiveness was good.

(Filtration performance evaluation)
As a result of evaluating the filtration performance using the obtained heat-resistant filter laminate, the circulation time was 15,000 seconds, the pressure loss was 190 Pa, the outlet concentration was 0.06 g / m ³ , and the dust collection rate was 99.9986%.

[Example 3]
(Spinning and sheeting)
A polyethylene terephthalate (PET) resin having an intrinsic viscosity (IV) of 0.63, a weight average molecular weight of 26000 and a melting point of 260 ° C. was dried at a temperature of 150 ° C. for 24 hours in a nitrogen atmosphere. This polyethylene terephthalate resin is melted by an extruder, the spinning temperature is 300 ° C., holes having a hole diameter (diameter) φ of 0.40 mm and 0.80 mm are alternately arranged, and spinning is performed using a spinning mouthpiece having a pitch of 1.6 mm. A single-hole discharge rate of 0.16 g / (minutes / holes) was spun from the mouthpiece, and compressed air at a temperature of 340 ° C. heated from an air heater at a discharge hole speed of 0.57 g / min was blown at a pressure of 0.45 MPa. , The melt-blown non-woven fabric having a grain size of 40 g / m ² and a thickness of 0.21 mm was obtained by collecting on a moving belt conveyor at a position of 100 mm from the spinneret. The number of fibers constituting the obtained melt-blown non-woven fabric has an average single fiber diameter of 3.0 μm, a mode of 1 μm, and a fiber abundance rate of 6.0 μm or more of 17%, and a shot (polymer mass) is formed by spinning for 1 hour. No occurrence occurred, and the spinnability was good.

(Physical properties of non-woven fabric)
The thickness of the obtained melt-blown non-woven fabric was 0.21 mm, and the air flow rate was 49 cm ³ / (cm ² seconds). The results are shown in Table 1.

(Heat treatment of non-woven fabric)
The same belt conveyor as in Example 1 was used, and heat treatment was performed under the same conditions. The heat shrinkage of the melt-blown non-woven fabric after the dry heat treatment was 0%, and no waviness, deterioration of the formation, and surface unevenness were observed. The results are shown in Table 1.

(Method of laminating non-woven fabric)
Under the same conditions as in Example 1, the felt and the bonding process were carried out to obtain a laminated non-woven fabric. The obtained heat-resistant filter laminate was sufficiently adhered, and the adhesiveness was good.

(Filtration performance evaluation)
As a result of evaluating the filtration performance using the obtained heat-resistant filter laminate, the circulation time was 14,000 seconds, the pressure loss was 200 Pa, the outlet concentration was 0.04 g / m ³ , and the dust collection rate was 99.9989%.

[Comparative Example 1]
(Spinning and sheeting)
A melt-blown nonwoven fabric was produced under the same conditions as in Example 1 except that the holes had a hole diameter (diameter) φ of only 0.40 mm and a discharge hole speed of 1.27 g / min was used using a spinneret having a pitch of 1.6 mm. The number of fibers constituting the obtained melt-blown non-woven fabric The average single fiber diameter is 3.5 μm, the mode is 3 μm, and the fiber abundance rate of 6.0 μm or more is 6%, and the shot (polymer mass) is formed by spinning for 1 hour. No occurrence occurred, and the spinnability was good.

(Physical properties of non-woven fabric)
The thickness of the obtained melt-blown non-woven fabric was 0.24 mm, and the air flow rate was 31 cm ³ / (cm ² seconds). The results are shown in Table 1.

(Heat treatment of non-woven fabric)
The same belt conveyor as in Example 1 was used, and heat treatment was performed under the same conditions. The heat shrinkage of the melt-blown non-woven fabric after the dry heat treatment was 0%, and no waviness, deterioration of the formation, and surface unevenness were observed. The results are shown in Table 1.

(Method of laminating non-woven fabric)
Under the same conditions as in Example 1, the felt and the bonding process were carried out to obtain a laminated non-woven fabric. The obtained heat-resistant filter laminate was sufficiently adhered, and the adhesiveness was good.

(Filtration performance evaluation)
As a result of evaluating the filtration performance using the obtained heat-resistant filter laminate, the circulation time was 13000 seconds, the pressure loss was 200 Pa, the outlet concentration was 0.07 g / m ³ , and the dust collection rate was 99.9986%.

[Comparative Example 2]
(Spinning and sheeting)
A melt-blown non-woven fabric was spun from a spinneret at a single-hole discharge rate of 0.12 g / (minutes / holes) at a discharge hole speed of 0.95 g / min under the same conditions as in Comparative Example 1 except for spinning. The number of fibers constituting the obtained melt-blown non-woven fabric The average single fiber diameter was 3.2 μm, the mode was 3 μm, and the fiber abundance rate of 6.0 μm or more was 4.9%. ) Was confirmed in some areas.

(Physical properties of non-woven fabric)
The thickness of the obtained melt-blown non-woven fabric was 0.23 mm, and the air flow rate was 26 cm ³ / (cm ² seconds). The results are shown in Table 1.

(Heat treatment of non-woven fabric)
The same belt conveyor as in Example 1 was used, and heat treatment was performed under the same conditions. The heat shrinkage of the melt-blown non-woven fabric after the dry heat treatment was 0%, and no waviness, deterioration of the formation, and surface unevenness were observed. The results are shown in Table 1.

(Method of laminating non-woven fabric)
Under the same conditions as in Example 1, the felt and the bonding process were carried out to obtain a laminated non-woven fabric. The obtained heat-resistant filter laminate was sufficiently adhered, and the adhesiveness was good.

(Filtration performance evaluation)
As a result of performing filtration performance evaluation using the obtained heat-resistant filter laminate, the circulation time was 9000 seconds, the pressure loss was 300 Pa, the outlet concentration was 0.06 g / m ³ , and the dust collection rate was 99.9986%.

[Comparative Example 3]
(Spinning and sheeting)
A melt-blown non-woven fabric with a basis weight of 40 g / m ² was produced under the same conditions as in Example 1 except that it was spun from a spinneret with a single-hole discharge rate of 0.32 g / (minutes / holes) and a discharge hole speed of 1.13 g / minute. did. The number of fibers constituting the obtained melt-blown non-woven fabric The average single fiber diameter was 7.8 μm, the mode was 7 μm, and the fiber abundance rate of 6.0 μm or more was 65%, and the shots (polymer lumps) were spun for 1 hour. No occurrence occurred, and the spinnability was good.

(Physical properties of non-woven fabric)
The thickness of the obtained melt-blown non-woven fabric was 0.26 mm, and the air flow rate was 82 cm ³ / (cm ² seconds). The results are shown in Table 1.

(Heat treatment of non-woven fabric)
The same belt conveyor as in Example 1 was used, and heat treatment was performed under the same conditions. The heat shrinkage of the melt-blown non-woven fabric after the dry heat treatment was 0%, and no waviness, deterioration of the formation, and surface unevenness were observed. The results are shown in Table 1.

(Method of laminating non-woven fabric)
Under the same conditions as in Example 1, the felt and the bonding process were carried out to obtain a laminated non-woven fabric. The obtained heat-resistant filter laminate was sufficiently adhered, and the adhesiveness was good.

(Filtration performance evaluation)
As a result of evaluating the filtration performance using the obtained heat-resistant filter laminate, the circulation time was 5000 seconds, the pressure loss was 350 Pa, the outlet concentration was 0.30 g / m ³ , and the dust collection rate was 99.9821%.

[Comparative Example 4]
(Spinning and sheeting)
A polypropylene (PP) resin having an MFR of 170 g / 10 min, a melting point of 162 ° C., and a weight average molecular weight of 83000 was used. This polypropylene resin is melted by an extruder, the spinning temperature is 260 ° C., holes having a hole diameter (diameter) φ of 0.30 mm and 0.60 mm are alternately arranged, and a single hole discharge amount is discharged from a spinneret having a pitch of 1.6 mm. Spinned at 0.16 g / (min / hole) at a discharge hole speed of 0.67 g / min, and compressed air at a temperature of 310 ° C. heated by an air heater was blown at a pressure of 0.25 MPa to spin the above-mentioned spinning. A melt-blown non-woven fabric having a grain size of 40 g / m ² was obtained by collecting on a moving belt conveyor at a distance of 150 mm from the base. The number of fibers constituting the obtained melt-blown non-woven fabric The average single fiber diameter is 3.5 μm, the mode is 3 μm, the fiber abundance of 6.0 μm or more is 10%, and the shot (polymer lump) is formed by spinning for 1 hour. No occurrence occurred, and the spinnability was good.

(Physical properties of non-woven fabric)
The thickness of the obtained melt-blown non-woven fabric was 0.23 mm, and the air flow rate was 80 cm ³ / (cm ² seconds). The results are shown in Table 1.

(Method of laminating non-woven fabric)
Under the same conditions as in Example 1, the felt and the bonding process were carried out to obtain a laminated non-woven fabric. The obtained heat-resistant filter laminate was sufficiently adhered, and the adhesiveness was good.

(Filtration performance evaluation)
As a result of performing filtration performance evaluation using the obtained heat-resistant filter laminate, tearing occurred at the time of aging 5000 times.

(Note) "Teflon (registered trademark)" resin: Polytetrafluoroethylene resin.

<Summary>
As shown in Table 1, by using a melt-blown non-woven fabric using a base having discharge holes (a) and discharge holes (b) having different hole diameters in Examples 1 to 3, the circulation time is longer than before. It was a low-pressure loss filter and was a non-woven fabric with the same or better filtration performance.

Further, in the melt blown non-woven fabric of the present invention, when a spinneret consisting of one hole is used as in Comparative Example 1, the mode of the single fiber diameter is 3 μm, and the performance including the outlet dust concentration is improved as compared with the conventional case. It was inferior to the invention. Further, when the fiber abundance rate of 6 μm or more was 5% or less as in Comparative Example 2, the circulation time and pressure loss were reduced, which was inferior to that of the present invention. Further, in the case of the melt-blown non-woven fabric having a number average single fiber diameter of 7.8 μm and a mode of 7 μm as in Comparative Example 3, dust penetrated into the melt-blow layer, and the circulation time and the dust concentration deteriorated. Further, in the case of a non-woven fabric made of polypropylene as in Comparative Example 4, it is presumed that the non-woven fabric made of polypropylene has a high molecular weight distribution and cannot be sufficiently thinned, and the mode is 3 μm, which is inferior to that of the present invention. The strength was also inferior to that of the present invention.

Claims (7)

A melt-blown nonwoven fabric composed of fibers containing a thermoplastic resin composition as a main component, wherein the mode of the single fiber diameter of the fibers is 1 μm, and the abundance rate of fibers of 6.0 μm or more is 5% or more. , Melt blow non-woven fabric. The melt-blown nonwoven fabric according to claim 1, wherein the number average single fiber diameter of the fibers is 0.1 μm or more and 5.0 μm or less. The melt-blown nonwoven fabric according to claim 1 or 2, wherein the thermoplastic resin composition has a weight average molecular weight of 75,000 or less. The melt-blown nonwoven fabric according to any one of claims 1 to 3, wherein the thermoplastic resin composition is a polyester resin or a polyarylene sulfide resin. A heat-resistant filter laminate in which at least one layer made of the melt-blown nonwoven fabric according to any one of claims 1 to 4 and a base cloth are bonded. The method for producing a melt-blown nonwoven fabric according to any one of claims 1 to 4, wherein the following steps (1) to (3) are sequentially performed.
Step (1): From the spinneret satisfying the following condition (i), the single-hole discharge rate of the thermoplastic resin composition is 0.20 g / (minutes / holes) or more and 1.10 g / (minutes / holes) or less. The process of spinning in a range to form threads.
Condition (i): A step (2): which has discharge holes (a) and discharge holes (b) having different hole diameters, and these are arranged alternately or regularly in a straight line in the width direction of the spinneret. When the melting point of the thermoplastic resin composition is Tm, a gas heated to (Tm + 10 ° C.) or higher (Tm + 50 ° C.) or lower and pressurized to 0.10 MPa or higher and 1.00 MPa or lower is applied to the threads. The process of spraying.
Step (3): A step of depositing the fibers on the collector. A method for producing a heat-resistant filter laminate, comprising a step of adhering at least one base fabric selected from the group consisting of a non-woven fabric, felt, woven fabric, and knitted fabric to the melt-blown non-woven fabric according to any one of claims 1 to 4.

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