JP6534942B2 - Melt blow non-woven fabric and use thereof - Google Patents

Description

  The present invention relates to a pliable, uniform, and liquid filter having excellent particle rejection, which is made of a polypropylene melt-blown non-woven fabric.

  Melt-blown non-woven fabrics are superior in flexibility to spunbond non-woven fabrics because they can be made into ultra-fine fibers, and can be laminated singly or with other non-woven fabrics etc. for filter applications, sanitary materials, clothing, It is used for packaging materials etc.

The melt-blown non-woven fabric using polypropylene is variously proposed to be applicable to a filter for precision filtration since it is excellent in chemical resistance and processability and excellent in the rejection of fine particles. For example, a filter element for precision filtration using a polypropylene non-woven fabric (melt-blown non-woven fabric) having an average pore diameter of 0.5 to 10 μm and a porosity of 30 to 80% has been proposed (Patent Document 1: 41284), Example 1 of Patent Document 1 is a composite integrated filtration material having a minimum pore size of 1.0 μm and a maximum pore size of 4.0 μm, which is formed by laminating three sheets of polypropylene meltblown nonwoven fabric and rebonding with a heating roll. And the rejection of polystyrene latex having a spherical particle size of 1 μm is described to be about 90%. Further, Patent Document 2 (International Publication Number: WO 2005/084777) is a non-woven fabric (melt-blown non-woven fabric) using a metallocene catalyst-polymerized polypropylene having a fiber diameter of 0.3 to 50 μm and a basis weight of 5 to 200 g / m ² filter cartridge made of has been proposed, in example 1 of Patent Document 2, average fiber diameter: 2.0 .mu.m, basis weight: to obtain a filter cartridge using a 30 g / m ² nonwoven fabric, the particles 99.9% It is stated that the size of the particles that can be removed is 6 μm.

On the other hand, in Patent Document 3 (Japanese Patent Application Laid-Open No. 2005-29931), since it is difficult to obtain a non-woven fabric in which fibers are uniformly dispersed, it is difficult to use a non-woven fabric obtained by applying an electric field to a spinning solution. A method has been proposed, and Comparative Example 5 of Patent Document 3 has an average pore diameter of 2.5 μm and a maximum pore diameter of 13. 5 μm, which comprises a polypropylene melt-blown nonwoven fabric having an average fiber diameter of 1.6 μm and a basis weight of 32 g / m ² . It is stated that the collection efficiency of the 7 μm filter medium is 17.0%.

Theoretically, in order to increase the rejection rate of fine particles, it is sufficient to decrease the average pore size and the maximum pore size of the non-woven fabric used, but as the average pore size decreases, the filtration efficiency such as pressure loss increases as the filtration time increases. There is a limit to reducing the average pore size because
As is clear from this situation, in the case of a liquid filter using a polypropylene melt-blown non-woven fabric, there is currently a limit to the rejection rate of fine particles (1 μm).

Japanese Examined Patent Publication 5-41284 International Publication WO2005 / 084777 JP 2005-29931 A

  The present invention is variously studied for the purpose of developing a liquid filter which is flexible, excellent in uniformity, and excellent in the rejection of fine particles without significantly reducing the flow rate by using a polypropylene melt-blown non-woven fabric. The result is Melt-blown non-woven fabric comprising fibers with an average fiber diameter of more than 1.0 μm is subjected to calendering etc. to make the maximum pore diameter not more than 5 μm and the average pore diameter not more than 2 μm. The blocking rate can not be 100%. According to the present invention, by setting the average fiber diameter of the fibers used for the polypropylene melt-blown nonwoven fabric to less than 1.0 μm, it is possible to obtain a liquid filter having 100% rejection of polystyrene latex particles having a spherical particle diameter of 1.00 μm. It is in finding out.

The present invention relates to the following [1] to [4].
[1] It consists of polypropylene ultrafine fibers having an average fiber diameter of 0.5 μm or more and less than 1.0 μm,
The maximum pore size measured at a basis weight of 60 g / m ² is 5 μm or less, and the average pore size is 2 μm or less,
The air permeability measured at a basis weight of 15 g / m ² is 3 to 7 cc / cm ² / sec,
100% rejection of polystyrene latex particles having a spherical particle diameter of 1.00 μm measured at a basis weight of 60 g / m ² ,
The rejection of polystyrene latex particles having a spherical particle diameter of 0.47 μm measured at a basis weight of 60 g / m ² is 10% or more, and
A melt-blown nonwoven fabric characterized by having a basis weight of 5 to 200 g / m ² .
[2] The melt-blown nonwoven fabric according to the above [1], which is used for a filter for liquid.
[3] It consists of polypropylene ultrafine fibers having an average fiber diameter of 0.5 μm or more and less than 1.0 μm,
The maximum pore size measured at a basis weight of 60 g / m ² is 5 μm or less, and the average pore size is 2 μm or less,
The air permeability measured at a basis weight of 15 g / m ² is 3 to 7 cc / cm ² / sec,
100% rejection of polystyrene latex particles having a spherical particle diameter of 1.00 μm measured at a basis weight of 60 g / m ² ,
The rejection of polystyrene latex particles having a spherical particle diameter of 0.47 μm measured at a basis weight of 60 g / m ² is 10% or more, and
A liquid filter comprising a melt-blown non-woven fabric having a basis weight of 5 to 200 g / m ² .
[4] The liquid filter according to the above [3], which is a liquid filter for precision filtration.
The present invention is for a liquid comprising a melt-blown non-woven fabric comprising polypropylene ultrafine fibers having an average fiber diameter of 0.5 or more and less than 1.0 μm and having a maximum pore diameter of 5 μm or less and an average pore diameter of 2 μm or less measured at 60 g / m ² It provides a filter.

  The filter for liquid according to the present invention has a flow rate which is not so low, a high rejection ratio of fine particles, an excellent filtration performance, and an excellent filter life and chemical resistance, so that the elution property is low and the recyclability is excellent.

<Polypropylene>
As polypropylene used for the raw material of the melt-blown nonwoven fabric used for the filter for liquids of this invention, a well-known polypropylene can be used. The polypropylene is usually a homopolymer of propylene having a melting point (Tm) of 155 ° C. or higher, preferably in the range of 157 to 165 ° C. or propylene and a very small amount of ethylene, 1-butene, 1-pentene, 1-hexene, It is a copolymer with one or more α-olefins of 2 or more carbon atoms, preferably 2 to 8 such as 1-octene, 4-methyl-1-pentene, etc., and a propylene homopolymer is preferable.
The melt flow rate (MFR: ASTM D-1238, 230 ° C., load 2160 g) is not particularly limited as long as the polypropylene according to the present invention can be melt-spun, but it is usually 1 to 1000 g / 10 min, preferably 5 to 500 g It is in the range of 10 minutes, more preferably 10 to 100 g / 10 minutes.

<Melt blow non-woven fabric>
The melt-blown nonwoven fabric according to the present invention is composed of polypropylene ultrafine fibers having an average fiber diameter of 0.5 or more and less than 1.0 μm, and the maximum pore size measured at a basis weight of 60 g / m ² is 5 μm or less, preferably 4.5 μm or less Is 2 μm or less, preferably, the minimum pore diameter is in the range of 1.0 μm or more.

Melt-blown nonwoven fabrics consisting of fibers with an average fiber diameter of 1.0 μm or more or melt-blown nonwoven fabrics having an average pore diameter of more than 2 μm measured at a basis weight of 60 g / m ² are polystyrene latexes having a spherical particle diameter of 1.00 μm Can not be 100%.

The melt-blown nonwoven fabric of the present invention preferably has an air permeability measured at a basis weight of 15 g / m ² in the range of 3 to 7 cc / cm ² / sec. Non-woven fabrics with an air permeability exceeding 7 cc / cm ² / sec may cause non-uniform dispersion of microfibers and an increase in average pore diameter, which may reduce the rejection of fine particles when used as a liquid filter. is there. On the other hand, in the case of a nonwoven fabric having an air permeability of less than 3 cc / cm ² / sec, there is a risk that the flow rate may be reduced (filtration time will be increased) when used for a liquid filter.

The melt-blown nonwoven fabric of the present invention preferably has an average pore diameter of at least 0.01 μm, preferably at least 0.1 μm, as measured at a basis weight of 60 g / m ² . If the average pore diameter measured at a basis weight of 60 g / m ² is less than 0.01 μm, the pressure loss may be high and the flow rate may not be produced when used in a liquid filter.

The melt-blown nonwoven fabric according to the present invention preferably has a blocking rate of 100% for a polystyrene latex having a spherical particle diameter of 1.00 μm and 3.00 μm measured at a basis weight of 60 g / m ² .
The meltblown nonwoven fabric according to the present invention more preferably has a blocking rate of 10% or more for a polystyrene latex having a spherical particle diameter of 0.47 μm measured at a basis weight of 60 g / m ² .

The basis weight of the melt-blown nonwoven fabric according to the present invention can be determined appropriately depending on the application of the liquid filter, but it is usually in the range of 5 to 200 g / m ² , preferably 10 to 150 g / m ² .

<Filter for liquid>
The liquid filter of the present invention comprises the melt-blown nonwoven fabric. The liquid filter of the present invention may be composed of a single layer of the melt-blown nonwoven fabric or may be composed of a laminate of two or more melt-blown nonwoven fabrics. When a laminate of two or more meltblown nonwoven fabrics is used as a liquid filter, two or more meltblown nonwoven fabrics may be simply overlapped.

  The liquid filter of the present invention may be calendered using, for example, a pair of flat rolls provided with a clearance between flat rolls in order to control the hole diameter to be small. The clearances between the flat rolls need to be appropriately changed depending on the thickness of the non-woven fabric so that the gaps between the fibers of the non-woven fabric are eliminated. When heat treatment is carried out during calendering, it is desirable that the roll surface temperature be thermally pressed in the range of 15 ° C. to 50 ° C. lower than the melting point of the polypropylene microfibers. When the roll surface temperature is lower than the melting point of the polypropylene ultrafine fibers in the range of less than 15 ° C., the melt-blown non-woven surface is filmed and the filter performance is inferior.

The filter for liquid of the present invention is composed of the melt-blown nonwoven fabric, but in accordance with the purpose and the liquid to be applied, a nonwoven fabric having a larger fiber diameter than a melt-blown nonwoven fabric (filter for liquid) having the above-mentioned performance is laminated. By doing this, the life of the liquid filter can be extended.
In addition, in order to increase the strength of the liquid filter, a spunbonded nonwoven fabric or a mesh may be laminated.

<Method of producing melt-blown nonwoven fabric>
The melt-blown nonwoven fabric of the present invention is obtained by the known melt-blown nonwoven fabric production method using the above-mentioned polypropylene. For example, polypropylene as a raw material is melted, discharged from a spinning nozzle, and exposed to high-temperature and high-pressure gas to collect fine fibered polypropylene ultrafine fibers in a collector such as a porous belt or a porous drum. Can be manufactured by depositing.

For each production condition, for example, the velocity (discharge air volume) of high-temperature and high-pressure gas is 4 to ³⁰ N mm ³ / min / m so that the average fiber diameter of polypropylene ultrafine fibers becomes 0.5 μm or more and less than 1.0 μm and desired thickness. The distance from the nozzle spinning discharge port to the collection surface (porous belt) may be 3 to 55 cm, and the mesh width of the porous belt may be 5 to 200 mesh.

Hereinafter, the present invention will be more specifically described based on examples, but the present invention is not limited to these examples.
Physical property values and the like in Examples and Comparative Examples were measured by the following methods.

(1) Average fiber diameter (μm)
A photograph of 1000 × magnification was taken with a meltblown nonwoven fabric using an electron microscope (S-3500N manufactured by Hitachi, Ltd.), 100 fibers were arbitrarily selected, the width (diameter) of the fibers was measured, and the obtained measurement results The average fiber diameter was taken as the average fiber diameter.

(2) Maximum pore size (μm), minimum pore size (μm) and average pore size (μm) measured at a basis weight of 60 g / m ²
A melt-blown nonwoven fabric with a basis weight of 60 g / m ² is prepared, and a nonwoven fabric laminate serving as a filtration material for water treatment in a thermostatic chamber at a temperature of 20 ± 2 ° C. and a humidity of 65 ± 2% specified in JIS Z8703 (standard state of test place). The test piece collected from the sample is immersed in a fluorine-based inert liquid (trade name: Florinate, manufactured by 3M), and capillary flow porometer (Model: CFP-1200AE) manufactured by Porous materials, Inc. The maximum pore size (μm), the minimum pore size (μm) and the average pore size (μm) measured at a basis weight of 60 g / m ² were measured using this method (indicated as “maximum pore size”, “minimum pore size” and “average pore size” in the table) ).

(3) Blocking rate (%) and flow rate (l / min)
A melt-blown non-woven fabric having a basis weight of 60 g / m ² was prepared, and a polystyrene latex particle having a spherical particle diameter of 1.00 μm was dispersed in a 60% by volume IPA aqueous solution at a concentration of 0.01% by weight. The concentration in the filtrate passing through the melt-blown non-woven fabric (filter for liquid): C ₁ and the concentration of the stock solution: C ₀ were measured under a pressure of 0.3 MPa with TSU-90B), and the inhibition rate was determined by the following equation.
The concentrations of the test solution and the filtrate were determined from a calibration curve measured in advance by measuring the absorbance at a wavelength of 500 nm using a spectrophotometer (UV3100 manufactured by Shimadzu).
Rejection = _{[(C 0 -C 1) / C} 0 ] × 100 (%)

In addition, using the polystyrene latex particles having a spherical particle diameter of 3.00 μm and a spherical particle diameter of 0.47 μm, the rejection was determined by the above method.
The flow rate (l / min) is the time when 500 cc of 60 volume% IPA aqueous solution passes through a meltblown non-woven fabric (filter for liquid) under a pressure of 0.3 MPa using the above-mentioned filtration apparatus (TSU-90B manufactured by ADVANTEC) I asked.

(4) Permeability (cc / cm ² / second)
A melt-blown non-woven fabric having a basis weight of 15 g / m ² is prepared, and a temperature of 20 ± 2 ° C. specified in JIS Z 8703 (standard state of test place) in accordance with JIS L 1096 (8.27.1 A method; Fraziled method). The amount of air passing through the test piece (cm ³⁾ was collected using a Frazier-type testing machine by collecting five 20 × 20 cm test pieces collected from the non-woven fabric laminate used as a filter material for water treatment in a constant temperature room with a humidity of 65 ± 2%. / Cm ² · seconds) was measured and the average value was determined.

Example 1
Propylene homopolymer (MFR: 25 g / 10 min) is supplied to the die using a melt-blown nonwoven fabric manufacturing apparatus, and the discharge amount per nozzle single hole from the die at the set temperature: 300 ° C .: 0.08 g / min. Discharge with heated air (300 ° C, 700 Nm ³ / hour / m) blown from both sides, DCD (distance from surface of spinneret to collector): 150 mm sprayed onto collector, weight per unit: 15 g / m ² melt blow I got a non-woven fabric.
Subsequently, four sheets of the melt-blown nonwoven fabric obtained were stacked to form a filter for liquid.
Physical properties of the obtained liquid filter were measured by the method described above. The results are shown in Table 1.

Comparative Example 1
Propylene homopolymer (MFR: 25 g / 10 min) is supplied to the die using a melt-blown nonwoven fabric manufacturing apparatus, and the discharge amount per nozzle single hole of the nozzle is 0.1 g / min from the die at a set temperature of 300 ° C. Discharge with heated air (300 ° C, 700 Nm ³ / hour / m) blown from both sides, DCD (distance from surface of spinneret to collector): 150 mm sprayed onto collector, weight per unit: 15 g / m ² melt blow I got a non-woven fabric.
Subsequently, four sheets of the melt-blown nonwoven fabric obtained were stacked to form a filter for liquid.
Physical properties of the obtained liquid filter were measured by the method described above. The results are shown in Table 1.

Comparative example 2
Propylene homopolymer (MFR: 25 g / 10 min) is supplied to a die using a melt-blown nonwoven fabric manufacturing apparatus, and the discharge amount per nozzle single hole from the die at a set temperature: 300 ° C .: 0.15 g / min. Discharge with heated air (300 ° C, 700 Nm ³ / hour / m) blown from both sides, DCD (distance from the surface of the spinneret to the collector): 350 mm on the collector, weight per unit: 15 g / m ² melt blow I got a non-woven fabric.
Subsequently, four sheets of the melt-blown nonwoven fabric obtained were stacked to form a filter for liquid.
Physical properties of the obtained liquid filter were measured by the method described above. The results are shown in Table 1.

Comparative example 3
Propylene homopolymer (MFR: 25 g / 10 min) is supplied to the die using a melt-blown nonwoven fabric manufacturing apparatus, and the amount of discharge per nozzle single hole: 0.5 g / min from a die with a set temperature of 300 ° C. heating air (300 ℃, 700Nm ³ / h / m) discharged from the discharge to Ban, DCD (distance from the surface of the spinneret to collector) by blowing the collectors 250 mm, basis weight: of 15 g / m ² meltblown non-woven fabric I got
Subsequently, four sheets of the melt-blown nonwoven fabric obtained were stacked to form a filter for liquid.
Physical properties of the obtained liquid filter were measured by the method described above. The results are shown in Table 1.

Comparative example 4
Using a calender roll processing apparatus, the nonwoven fabric laminate in which four sheets of the meltblown nonwoven fabric obtained in Comparative Example 1 are laminated is used for heat bonding using a combination of metal rolls for the second stage calender roll used for thermal bonding. The roll temperature: 50 ° C., linear pressure: 10 kg / cm, to obtain a liquid filter.
Physical properties of the obtained liquid filter were measured by the method described above. The measurement results are shown in Table 1.

As apparent from Table 1, it is made of a polypropylene ultrafine fiber having an average fiber diameter of 0.8 μm, for a liquid comprising a melt-blown non-woven fabric having a maximum pore diameter of 3.85 μm and an average pore diameter of 1.58 μm measured at 60 g / m ² The filter has 100% rejection of polystyrene latex particles having spherical particle sizes of 1.00 μm and 3.00 μm, and 12% polystyrene latex particles having spherical particle size of 0.47 μm, and the flow rate is 0.47 l / l. It is excellent in min (Example 1) and the rejection rate of microparticles | fine-particles.

  On the other hand, a melt-blown nonwoven fabric comprising polypropylene fibers having an average fiber diameter of 1.1 μm (comparative example 1), 1.5 μm (comparative example 2) and 3.0 μm (comparative example 3) and an average fiber diameter of more than 1.0 μm. The average particle diameter and the maximum particle diameter are large, and the rejection of fine particles is inferior to that of spherical particles of 1.00 μm polystyrene latex particles with 90%, 64% and 2% and 100%, respectively.

  Further, a liquid filter (comparative example 4) in which a melt-blown non-woven fabric composed of polypropylene fibers having an average fiber diameter of 1.1 μm was calendered to make the average pore diameter and the maximum pore diameter the same as in Example 1 was spherical particle diameter 1. The rejection of polystyrene latex particles of 00 μm and 3.00 μm does not reach 97%, 99% and 100%, and the flow rate is low and the filtration efficiency is poor.

  The liquid filter made of the melt-blown non-woven fabric of the present invention is excellent in uniformity, and is excellent in the rejection of fine particles of 1 μm, so that it can be used for a liquid filter for precision filtration.

Claims (2)

It consists of polypropylene microfibers with an average fiber diameter of 0.5 μm or more and less than 1.0 μm,
The maximum pore size measured at a basis weight of 60 g / m ² is 5 μm or less, and the average pore size is 2 μm or less,
The air permeability measured at a basis weight of 15 g / m ² is 3 to 7 cc / cm ² / sec,
100% rejection of polystyrene latex particles having a spherical particle diameter of 1.00 μm measured at a basis weight of 60 g / m ² ,
The rejection of polystyrene latex particles having a spherical particle diameter of 0.47 μm measured at a basis weight of 60 g / m ² is 10% or more, and
A melt-blown nonwoven fabric characterized by having a basis weight of 5 to 200 g / m ² .   The melt-blown nonwoven fabric according to claim 1, which is used for a filter for liquid.