JP2001098453A - Electret nonwoven fabric and air filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a highly electrified electret nonwoven fabric and produce an air filter having an excellent dust collecting power. SOLUTION: This electret nonwoven fiber is obtained by spinning sheath-core type conjugate filaments of polybutene-1 and polypropylene according to a melt blowing method on a nonwoven fabric of a base fabric, providing a laminated nonwoven fabric, carrying out an electrification processing of the laminated nonwoven fabric in an atmosphere at the melting temperature of the polybutene-1 or above and quenching the resultant laminated nonwoven fabric under application of a voltage. A product of a melt blown nonwoven fabric or a spunbonded nonwoven fabric having a low Metsuke (mass per unit area) is used as the base fabric. The laminated nonwoven fabric has performances excellent as an air filter for an air cleaner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electret nonwoven fabric comprising polybutene-1 which can be electret-processed to a higher charged voltage than the conventional polypropylene electret nonwoven fabric, and an electret component and a heat bonding component.
Since the fibers can be charged to a high charge, if the dust collection efficiency is the same as that of the conventional type, thicker fibers can be achieved with fewer fibers and the electret filter can have a lower pressure loss. And an electret nonwoven fabric which is extremely useful as an air filter such as a mask for hay fever and a filter for an air purifier.

[0002]

2. Description of the Related Art Polybutene-1 has a melting point of about 130 DEG C.
As is known for the core component of the sheath-core type composite fiber of No. 17, the fibers are easily fixed to each other by polybutene-1, and this fixation is avoided by the present inventors as shown in JP-A-5-179511. A condition has been discovered. Japanese Unexamined Patent Publication No. 5-19539 discloses a nonwoven fabric using polybutene-1.
No. 9 and JP-A-5-214655 are known.

[0003]

Since polybutene-1 has a different steric structure from other polyolefins, it has a unique crystal morphology, a low crystallization rate, melt spinning, and cooling in a draft with cold air. Also, sticking (fusing) occurred between the fibers to be bundled, and it was difficult to form fibers. Polybutene-1 has a longer side chain than polypropylene or polyethylene, and has a large molecular weight even at the same MI (measurement of melt fluidity), so that it has a large ballistic effect and is inferior in melt spinnability, so that fiberization was difficult. However, since polybutene-1 has a high softening temperature and can withstand continuous use even at a high temperature of about 100 ° C., and has a better charging property than polypropylene, the electret nonwoven fabric containing polybutene-1 is used for air conditioning air filters and the like. Can also be used conveniently. Therefore, it has been desired that polybutene-1 be efficiently fiberized and used like other polyolefins such as polypropylene.

The present inventors have found that polybutene-1 has an appropriate ballistic effect and improves spinnability when a polymer having a narrow molecular weight distribution with a Q value of less than 3 is selected. In order to produce fine fibers, if the resin having a high MI is used, or if the spinning temperature is increased to lower the viscosity of the molten resin, there is a problem that fusion between the fibers becomes remarkable.
It is necessary to have a high level of technology to stably produce staple fibers of polybutene-1 composite fibers with a fineness of dtex or less, and the staple fibers are provided with a fiber treatment agent to ensure card passing properties. It is technically difficult to produce an electret nonwoven fabric using the method described above, and it has been necessary to judge that this method cannot be easily used.

[0005]

Means for Solving the Problems The present inventors diligently studied a method for easily and easily producing an electret nonwoven fabric using a polybutene-1 composite fiber. The electret nonwoven fabric using the polybutene-1 composite fiber can be obtained by electret processing of a nonwoven fabric, and the present inventors have studied the direct conversion of the polybutene-1 composite fiber into a nonwoven fabric, and reached the present invention.

In other words, the property that polybutene-1 is easily fused is positively utilized in the formation of a nonwoven fabric, and a polybutene-1 composite fiber is ejected from a single-row nozzle composite melt blow nozzle, and the net is suctioned and evacuated from below. Laminating on a non-woven fabric such as a spun-bonded non-woven fabric on a conveyor to form a non-woven fabric, and using a net conveyor type hot air penetration type thermal bonding processing machine equipped with a DC high voltage application device inside and outside the processing machine, polybutene-1 is formed. The electret nonwoven fabric could be easily obtained by performing charging at a temperature equal to or higher than the melting point, quenching the film under application of electric current, and winding.

That is, according to the present invention, the Q value (weight average molecular weight) / number average molecular weight ratio is less than 3, the melt index (MI: g / 10 minutes, the measurement temperature is 190 ° C., the weight is 2.1).
69 kg, according to JIS-K-6760) 0.5 <M
I <50, density (D: g / cm ³ ) is 0.905 ≦ D <
0.930, melting point (Tm: ° C) 115 <Tm <130
Having the melting point (Tm:
C) of 140 <Tm <270 as a second component, a sheath-core composite fiber having a second component as a core component, a first component as a sheath component, and / or a spine comprising both components. One side of a polybutene-1 composite fiber layer composed of a belly-type composite fiber and / or a mixed spun fiber of both components and bonded and integrated with polybutene-1 has polypropylene and / or
Or a combination of polyethylene terephthalate and / or a resin having a melting point (Tm: ° C.) of 90 <Tm <230 and a resin having a melting point of at least 20 ° C. higher and at least 20 ° C. higher than the melting point of polybutene-1. A spunbonded nonwoven fabric and / or a meltblown nonwoven fabric composed of a plurality of thermoplastic resins are bonded and integrated with polybutene-1, and at least polybutene-1 is charged. It is an electret nonwoven fabric.

One of the preferred embodiments of the present invention is that the first component is a sheath component, the second component is a core component, and the fineness is 5d.
20 to 80 g / m ² , made of sheath-core composite meltblown fibers containing long fibers having a tex of 0.1 to 0.1 dtex.
On one side of the polybutene-1 conjugate fiber layer of the present invention, a spunbond nonwoven fabric made of polypropylene and having a fineness of constituent fibers of 5 dtex or less, or the fineness of the constituent fibers is 0.1 d
The electret nonwoven fabric is a composite nonwoven fabric obtained by laminating melt-blown nonwoven fabrics having a tex or less and a nonwoven fabric having a basis weight of 10 to 60 g / m ² .

In another aspect of the present invention, a Q value (weight average molecular weight) / number average molecular weight ratio is less than 3, a melt index (MI: g / 10 minutes, a measurement temperature of 190 ° C., a load of 2.169 kg, According to JIS-K-6760).
5 <MI <50, density (D: g / cm ³ ) 0.905
≦ D <0.930, melting point (Tm: ° C.) 115 <Tm <
Polybutene-1 having a melting point of 130 (Tm:
C) of 140 <Tm <270, a polybutene-1 composite fiber layer having a basis weight of 20 to 80 g / m ² , which is composed of a sheath-core composite meltblown fiber having a fineness of 5 to 0.1 dtex and a fiber moldable thermoplastic resin as a core component. Is a spunbonded nonwoven fabric made of polypropylene fiber having a fineness of 5 dtex or less or a composite nonwoven fabric obtained by laminating a melt-blown nonwoven fabric having a fineness of 0.1 dtex or less on the nonwoven fabric with a basis weight of 1 dtex or less.
0~60g / m 1 sheet ² of nonwoven fabric composite nonwoven fabric are adhered or are plurally stacked, it is please refer to the guidance document filter formed by using the electret non-woven fabric at least polybutene-1 is charged.

[0010] Still another preferred embodiment of the present invention is the above air filter, wherein a prefilter layer is provided on the air inflow side of the electret nonwoven fabric.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Polybutene-1 is extremely easy to fuse by melt spinning, and in a production method having a process of bundling melted and solidified fibers such as staples, multifilaments and spunbonds, polybutene-1 is in a bundled state at the time of bundling. Since fusion occurs, it becomes a serious problem in the process of forming a nonwoven fabric. Therefore, in the nonwoven fabric of the present invention, using a melt blow spinning facility in which the nozzle holes are arranged in a line, at least a portion where the fibers intersect or contact with each other by jetting the individual fibers onto the conjugate fibers on the net conveyor. A part was fused to form a composite fiber. In addition, adhesion to the conjugate fiber on the net conveyor also occurs in the same manner. However, in such bonding by fusion, even if adjustment between the conveyor and the nozzle or adjustment of the air temperature of the discharged hot air is not sufficient, the practical strength of the nonwoven fabric is not sufficient. Performed during processing.

The use of a nonwoven fabric such as a spunbonded nonwoven fabric as the base fabric is intended to prevent the spouted polybutene-1 composite fibers from fusing with each other to form a heat-bonded nonwoven fabric and from sticking to the conveyor. Since the polybutene-1 composite fiber is not stretched, it has a low nonwoven fabric strength and is used for reinforcement. The base fabric is finally used for the polybutene-1 composite fiber layer and the polybutene-1 layer during the charging process under heating. Heat bonded.

In the melt-blow spinning in which the nozzle holes are arranged in a line, when hot air is blown out neatly, the fibers blow out neatly in a mound-like manner and accumulate on the non-woven fabric. It is easy to control the fibers so that they do not fuse with adjacent fibers.
Melt blow spinning is an essential element.

The 5 dtex polybutene-1 conjugate fiber is a continuous fiber like the fiber of a spun-bonded non-woven fabric. However, as the fineness becomes smaller, a finite length fiber of the conventional melt blown fiber shape is gradually generated. And mixed into continuous fibers. If it is less than 0.1 dtex, meltblown fibrous fibers are mainly used, and the air flow resistance (pressure loss) is remarkably increased. Therefore, it is not preferable. An aggregate of fibers having a fineness of 5 to 0.1 dtex is most preferable. In particular, when the fineness is large, the pressure loss is small and the filtration efficiency is good as a filter.

The polybutene-1 used in the present invention has a melt index (MI: g / 10 minutes, a measurement temperature of 190 ° C., a weight of 2.169 kg, and a measurement method of JI for convenience of composite spinning.
SK-6760) is preferably set to 0.5 <MI <50, and if it is 0.5 or less, composite spinning is difficult, and if it is 50 or more, the resin to be combined becomes too high in fluidity, and fiber It is not preferable because the stiffness is weak and a non-woven fabric is formed. For convenience of composite melt spinning, polybutene-1 having a density (D: g / cm ³ ) of 0.905 ≦ D <0.930 and a melting point (Tm: ° C.) of 115 <Tm <130 is preferable. Those outside the range are not preferred because they are inferior in melt spinnability.

The fiber-forming thermoplastic resin as the second component of the polybutene-1 conjugate fiber of the present invention has a melting point (Tm: ° C.) of 1%.
Polypropylene having a relationship of 40 <Tm <165 is preferable, and a copolymerized polypropylene having a melting point of 140 ° C. or lower is too soft, and the fiber has no elasticity.

The polybutene-1 composite fiber of the present invention may be a fiber in which at least a part of the fiber surface is occupied by polybutene-1, and more preferably, the entire fiber surface is
Fibers occupied by polybutene-1 are good. In particular,
Sheath-core type composite fiber having polybutene-1 as a sheath component, dorsal ventral type composite fiber containing polybutene-1 as one component, and polybutene-1
Preferred is a mixed spun fiber of polypropylene and polypropylene, and the sheath-core conjugate fiber includes an eccentric type and a heterogeneous core type, and the heterogeneous core type includes a split type conjugate fiber, and these fibers are also included in the present invention. It can be used conveniently.

The polybutene-1 composite fiber of the present invention is bonded and integrated at least with polybutene-1 to form a polybutene-1 composite fiber layer. Since the polybutene-1 composite fiber layer immediately after melt-blow melting is laminated on the base cloth without being solidified, the base cloth and the composite fiber layer are similarly bonded and integrated with at least the polybutene-1. As described above, the adhesion at this point is due to the fusion of polybutene-1 and the adhesive strength is weak. Therefore, full-scale thermal adhesion in which polybutene-1 is melted at the time of charging under heating is performed again.

The non-woven fabric used for the base fabric is made of polypropylene or polyethylene terephthalate, or a combination of resins having a melting point (Tm ° C.) lower than that of polybutene-1 by at least 20 ° C. and in the range of 90 <Tm <230. A spunbonded nonwoven fabric or a meltblown nonwoven fabric composed of a plurality of thermoplastic resins, or a laminated nonwoven fabric thereof, to which a fiber treating agent such as an antistatic agent is not attached, is conveniently used. Among the spunbonded nonwoven fabrics, those having a point bond thermal bond are preferable because of their high nonwoven fabric strength. The basis weight is 1
0 g / m ² is good if, since when serving as a prefilter may Some ^{60g / m 2, 10~60g / m} 2
Is convenient.

In the embodiment of the present invention, a spunbond nonwoven fabric having a fineness of 2.6 dtex and a basis weight of 20 g / m ² is used in the embodiment of the present invention, and the pressure loss of the base fabric is a polybutene-1 composite. It can be said that it is almost negligible compared to the fiber layer. Therefore, the electret nonwoven fabric of the present invention in which this base fabric is combined with the polybutene-1 composite fiber layer having a relatively large fineness has a low pressure loss as an air filter, and a filter having good filtration efficiency can be obtained.

The charging process of the polybutene-1 is performed by passing the nonwoven fabric through a polybutene-1 nonwoven fabric in a high-voltage electric field with a direct current in an atmosphere at a temperature equal to or higher than the melting point of the polybutene-1, and quenching in a high-voltage electric field with a direct current to at least 60%. It can be achieved by setting the temperature to not more than ° C. It is a matter of course that electret processing can be performed by using a charging processing method other than the above method, for example, a general method such as corona discharge processing. in this case,
The polybutene-1 nonwoven fabric can be melt-bonded with a polybutene-1 using a hot air penetration type thermal bonding machine or a hot roll processing machine in advance to prevent delamination between the polybutene-1 composite fiber layer and the base fabric. preferable.

The basis weight of the fiber layer made of polybutene-1 conjugate fiber of the present invention will depend on the basis weight of the base fabric, when the basis weight of the base fabric and 20 g / m ^2, preferably 20 to 80 g / m ^2, the Outside the range, it becomes difficult to obtain highly charged polybutene-1 fibers. The electret nonwoven fabric of the present invention is
Although one layer can be used, the collection efficiency can be improved by using two or more layers, and it is very preferable to use a plurality of layers. It is also preferable that the electret nonwoven fabric of the present invention has an antibacterial function, a deodorant function, or the like provided at least in part.

The air filter referred to in the present invention is not only a filter for building air conditioning, but also a mask for hay fever, a filter for an air purifier, a garbage pack and an exhaust port filter for a vacuum cleaner, and a vent filter for electronic equipment. It is intended to be used for removing dust inside.

The polybutene-1 used in the present invention has a Q value of 3
Since it is smaller than less, a moderate ballistic effect is produced during melt spinning, which is convenient. Since this is combined with another resin having excellent fiber forming properties, spinnability is further improved. Polybutene-1 has a relatively low melting point of 115 to 130 ° C., and in the present invention, it is a composite fiber of this and another resin having a high melting point. The form is maintained and processing is easy, and the heat processing machine may be a general-purpose machine. Furthermore, polybutene-1 has a longer side chain than polypropylene or polyethylene, and is easily polarized, and is thermally bonded in hot air and, at the same time, is subjected to charging treatment, whereby an excellent electret nonwoven fabric can be obtained in one step. The obtained non-woven fabric is hard and stiff, and when pleating is required for use in air filters for building air conditioning, etc., it is easier to mold than conventional polypropylene, for example, and no reinforcing material such as mesh fabric is required. It is. Furthermore, the practical use temperature is 100 ° C., and the use range is wider than 70 ° C. of polypropylene, which is most suitable as a dust collection filter for temperature control.

[0025]

EXAMPLES Examples 1 to 9 The following four types of polymers were combined and melt-spun into sheath-core type composite fibers, spine-type composite fibers and mixed fibers. Type of polymer Symbol Polypropylene PP Polybutene-1 PB (Polybutene-1
Were selected from Buron and Tuffmer brands manufactured by Mitsui Chemicals, Inc. Polyethylene PE polyethylene terephthalate PET melt spinning uses a high pressure hot air at the same temperature as the nozzle temperature to blow out a molten polymer from a 203-hole composite melt blow nozzle of about 60 cm, and sucks this with a suction amount of 5 times or more the amount of hot air blown out. Accumulated on the base cloth on the net conveyor. At this time, a composite nonwoven fabric in which the molten polymer was fused and temporarily bonded to be integrated with the base fabric was obtained. The base fabric is the following two types of polypropylene spunbond nonwoven fabric manufactured by Mitsui Chemicals, Inc. SB fineness 2.6DTex, basis weight 20 g / m ^2, thickness 0.01 mm M / S SB of 17 g / m ² basis weight composite article formed by laminating a 6 g / m ² basis weight of fineness 0.07dTex meltblown nonwoven products. The obtained composite nonwoven fabric is treated for 5 minutes by applying a negative DC of 9 Kv to a 137 ° C. hot air penetration type heat bonding processing machine equipped with a DC high voltage applying device in which needles are embedded at regular intervals inside and outside the processing machine. The mixture was rapidly cooled under a direct current, grounded to static electricity, and rolled up to obtain a heat-bonded electret nonwoven fabric. Table 1 shows the polymer of each example, the structure of the nonwoven fabric, and the dust collecting effect of the obtained electret nonwoven fabric as a filter.

[0026]

[Table-1]

The measuring method of the measured value in the embodiment is as follows. The fineness of the fiber was calculated by taking a photograph of the constituent fibers of the nonwoven fabric with an electron microscope and calculating the fiber diameter. The charged voltage is a value obtained by wrapping a sample in a polyethylene film in a dust-free state, leaving it in a cool and dark place for three days or more, placing it between aluminum plates, removing static electricity, and then applying a charge meter. The strength, elongation and thickness of the nonwoven are 5
A sample having a cm width was measured according to JISL-1096. Mask-based collection efficiency was measured by a dust mask performance test method based on the Industrial Safety and Health Act.

The electret nonwoven fabric of the present invention has a high dust-collecting force when used in an air filter. Therefore, when the dust-collecting force is equivalent to that of a conventional polypropylene nonwoven fabric, the pressure loss is low and the air permeability is high. A low air filter can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) D04H 3/16 D04H 3/16 F term (Reference) 4D019 AA01 BA13 BB03 BB04 BB10 BC01 BD01 DA06 4F100 AK01A AK04 AK07A AK07B AK08A AK41B BA02 BA14 DG15A DG15B DG17B DG20A GB72 JA04A JA06A JA13A JB16A JG03 JG03A YY00A 4L047 AA14 AA21 AA27 AA28 AB03 AB08 AB10 BA09 BB09 CA19 CB10 CC03 CC12 CC12

Claims (4)

[Claims] 1. A Q value (weight average molecular weight) / number average molecular weight ratio of less than 3 and a melt index (MI: g / 10)
Min, measurement temperature 190 ° C, weight 2.169kg, JIS-
Polybutene having a density of 0.5 <MI <50, a density (D: g / cm ³ ) of 0.905 ≦ D <0.930, and a melting point (Tm: ° C.) of 115 <Tm <130 (according to K-6760). −1 as the first component, and the melting point (Tm: ° C.) is 140 <T
m <270 fiber-forming thermoplastic resin as the second component,
A sheath-core type composite fiber having a second component as a core component and a first component as a sheath component, and / or a spine-type composite fiber comprising both components and / or a mixed spun fiber of both components. One side of the bonded and integrated polybutene-1 composite fiber layer has a polypropylene and / or polyethylene terephthalate and / or a melting point (Tm: ° C) of 9
A resin having a melting point of 0 <Tm <230 and a melting point of at least 20 ° C. higher than that of polybutene-1 and at least 2 ° C.
A spunbonded nonwoven fabric and / or a meltblown nonwoven fabric composed of a plurality of thermoplastic resins composed of a combination of resins having a melting point of 0 ° C. or higher are located, bonded and integrated with polybutene-1, and at least polybutene- An electret nonwoven fabric, wherein 1 is charged. 2. A unit weight of 20 to 80 g of a sheath-core composite meltblown fiber containing a long fiber having a fineness of 5 dtex to 0.1 dtex, wherein the first component is a sheath component and the second component is a core component. / M ² on one side of the polybutene-1 composite fiber layer, the fineness of the constituent fibers made of polypropylene is 5 dt.
^2. The electret nonwoven fabric according to claim 1, wherein the nonwoven fabric has a basis weight of 10 to 60 g / m ² and is a spunbonded nonwoven fabric of ex or less, or a composite nonwoven fabric in which a melt-blown nonwoven fabric having a fiber size of 0.1 dtex or less is laminated on the nonwoven fabric. . 3. The Q value (weight average molecular weight) / number average molecular weight ratio is less than 3, and the melt index (MI: g / 10)
Min, measurement temperature 190 ° C, load 2.169kg, JIS-
Polybutene having a density of 0.5 <MI <50, a density (D: g / cm ³ ) of 0.905 ≦ D <0.930, and a melting point (Tm: ° C.) of 115 <Tm <130 (according to K-6760). -1 as a sheath component, and a melting point (Tm: ° C) of 140 <Tm <2
The fineness of which is 70 as the core component of the fiber moldable thermoplastic resin of 70
On one surface of a polybutene-1 composite fiber layer having a basis weight of 20 to 80 g / m ² composed of a sheath-core composite meltblown fiber having a fineness of 5 dtex or less, a spunbonded nonwoven fabric composed of a polypropylene fiber having a fineness of 5 dtex or less, A composite nonwoven fabric in which a melt-blown nonwoven fabric having a fineness of 0.1 dtex or less is laminated, and at least one of the composite nonwoven fabrics to which a nonwoven fabric having a basis weight of 10 to 60 g / m ² is adhered or at least polybutene-1 is charged. Air filter using electret nonwoven fabric. 4. The air filter according to claim 3, wherein a prefilter layer is provided on the air inflow side of the electret nonwoven fabric.