JPH0559654A - Cylindrical nonwoven fabric made into electret and its production - Google Patents

Abstract

PURPOSE:To obtain the title nonwoven fabric having excellent adsorbability, filtering characteristics, excellent strength, neither elongating nor breaking, having no sewed part by transporting a fibrous material with a fluid and treating by a specific method. CONSTITUTION:First, a fibrous material 4 is transported with a fluid and a web 8 made into electret is formed while collecting the fibrous material on a first rotator 6 in a DC electric field. Then, the web 8 is transferred from the first rotator 6 to a second rotator 9 and formed into a cylindrical material 10 on the second rotator 9. Finally, the formed cylindrical material 10 is taken out in the axial direction of the second rotator 9 to give the objective nonwoven fabric 12 having >=1X10<-10> Coulomb/cm<2> surface charge density. The DC electric field is preferably produced between an impressed electrode 5 and the earthed first rotator 6 by using a DC high-voltage generator 7. The first rotator is preferably composed of a porous material through which a fluid is passed and the second rotator has preferably the surface having low frictional resistance such as aventurine surface.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel nonwoven fabric and a method for producing the same.

[0002] Specifically, the electrical adsorption, filterability,
TECHNICAL FIELD The present invention relates to a tubular electret nonwoven fabric having mechanical strength and a method for producing the same. The fields of application are bag filters, vacuum cleaner filters, copy filters, wipers, hair caps, masks and the like.

[0003]

2. Description of the Related Art Heretofore, there is no prior art relating to a tubular electretized nonwoven fabric and a method for producing the same. on the other hand,
There is conventional technology relating to a method for manufacturing a tubular nonwoven fabric. As disclosed in Japanese Patent Publication No. 56-48624, the method is to make a molten polymer extruded from an orifice into a fiber by a heat jet flow, collect the fiber in a rotating body, and directly form a cylinder on the fiber. It is a method of forming a non-woven fabric. In this method, the still softened fibers are collided with the jet stream of high wind speed on the rotating body to form a cylindrical nonwoven fabric, so that the cylindrical nonwoven fabric firmly adheres to the collecting rotating body. Therefore, it is difficult to pull out the tubular nonwoven fabric from the collection rotating body, and
When manufacturing a tubular non-woven fabric that has a drawback of tearing or high basis weight, if a large amount of fibers are deposited on the collection surface, a high-speed heat jet flow blows away the deposited fibers, so that a uniform tubular non-woven fabric can be obtained. There was also the drawback that it could not be done. Furthermore, there is a drawback that the diameter of the tubular nonwoven fabric cannot be freely changed.

Also, as a method for producing an electretized nonwoven fabric, there is Japanese Patent Publication No. 59-124, and it is necessary to sew both ends in order to obtain a tubular nonwoven fabric obtained by this method. In this case, there are drawbacks that the strength of the sewn portion is reduced, the adsorptivity is reduced due to the presence of the sewing thread, and the trapping efficiency is reduced when used in the filter.

[0005]

Therefore, the present invention solves the above-mentioned drawbacks and is excellent in adsorptivity, filterability, and strength.
A tubular electret non-woven fabric having no sewn portion and a method for producing the same are provided.

[0006]

The tubular electretized nonwoven fabric of the present invention has a surface charge density of 1 × 10 ^-10 coulomb /
A tubular electretized non-woven fabric having a size of not less than cm ² . The method for producing a tubular electretized nonwoven fabric of the present invention comprises: forming a electretized web while collecting a fibrous material conveyed by a fluid on a first rotating body in a DC electric field; Is moved from the first rotating body to the second rotating body, a tubular object is formed on the second rotating body by the web, and the formed tubular object is pulled out in the axial direction of the second rotating body. It is a method for producing a characteristic tubular electret nonwoven fabric.

Alternatively, in the method for manufacturing a tubular electret nonwoven fabric of the present invention, the web is formed after the fibrous material conveyed by the fluid is collected on the first rotating body, and then the web is formed. The first rotating body was moved to the second rotating body, and a DC electric field was created between the applying electrode and the second rotating body on the second rotating body to form a tubular object made of the electretized web. After that, the tubular object is pulled out in the axial direction of the second rotating body, which is a method for producing a tubular electret nonwoven fabric.

Alternatively, in the method for producing the tubular electretized nonwoven fabric of the present invention, the electretized web is collected while collecting the fibrous material conveyed by the fluid on the first rotating body in the DC electric field. When the web is moved from the first rotating body to the second rotating body after the formation of the web, and a cylindrical object made of the web is formed on the second rotating body, the applying electrode and the second rotating body are further formed. A method for producing a tubular electretized nonwoven fabric, characterized in that a direct current electric field is created between them to produce an electretized tubular article, and the tubular article is drawn out in the axial direction of the second rotating body.

[0009]

The present invention will be described based on embodiments.

FIG. 1 is a perspective view showing a model of the structure of a tubular electretized nonwoven fabric 1 of the present invention.

The tubular electretized nonwoven fabric 1 of the present invention
Has a tubular structure as shown in FIG. 1, and the nonwoven fabric is an electretized nonwoven fabric having a surface charge density of 1 × 10 ⁻¹⁰ coulomb / cm ² or more.

Further, the outer surface and the inner surface have different electric polarities, and the electret fibers 2 inside have a structure in which they are oriented and polarized in the thickness direction as shown in FIG.

FIG. 3 is a view of a manufacturing apparatus for forming the tubular electretized nonwoven fabric of the present invention as seen from a side surface direction (a rotation axis direction of a rotating body described later), and FIG. 4 is an oblique view thereof. It is the perspective view seen.

The molten polymer extruded from the melt-blowing mouthpiece 3 is made into a melt-blowing fiber 4 by a heat jet flow, and this fiber 4 is between the applying electrode 5 and the first rotating body 6 grounded.
In the DC electric field formed by using the DC high voltage generator 7,
The electretized web 8 is formed by collecting on the first rotating body 6. It is moved to the second rotating body 9, and the electretized tubular material 10 is formed thereon.

When forming the electretized web 8 on the first rotating body 6, it is possible to use the suction 11 for sucking the heat jet flow.

The electretized tubular material 10 thus formed is successively drawn out in the axial direction of the second rotating body 9 to produce a tubular electretized nonwoven fabric 12. When forming the electretized tubular material 10, the electretized web 8 is still formed.
If the fibers are softened, it is possible to form the electretized tubular article 10, but if not, it is preferable that the third rotating body 13 performs pressure bonding or thermocompression bonding. Further, as a method for joining the electretized tubular article 10 other than the above, a bonding method using a non-contact heat source, a spray bonding method using a chemical adhesive, a spray bonding method using hot melt, or the like can be used.

The manufactured tubular electret non-woven fabric 1
2 is received by the take-up box wheel 15 by the take-off roller 14 that rotates at a speed synchronized with the second rotating body 9. As another method for taking up the tubular electretized nonwoven fabric 12, it is possible to take up the tubular electret nonwoven fabric 12 at the same time while taking it up. It is also possible to cut the tubular non-woven fabric 12 in the length direction with a knife when taking it out to make a continuous flat non-woven fabric.

As shown in FIG. 5, the second rotating body 9 is
In order to make it easier to pull out the electretized tubular product in the axial direction, it is preferable to make the diameter of the second rotating body small in the pulling out direction. The basis weight of the tubular electretized nonwoven fabric can be changed depending on the amount of fiber to be conveyed, the speed of the second rotating body, and the drawing speed of the tubular object.

FIG. 6 shows an embodiment of a method for changing the diameter of a tubular electret nonwoven fabric. Melt blow base 3
3 and 4 until the electretized web 8 is formed by using the electretized tubular material 1
The second rotating body 9 forming 0 is different. That is, the second rotating body 9 is composed of at least two rotating bodies.

In this embodiment, the main rotary body 16 and the sub rotary body 17 are provided. The positions of the two rotating bodies can be freely changed, and thus the diameter of the cylindrical object can be changed. The formed electretized tubular product 10 is bonded by the third rotating body 13 and sequentially pulled out in the axial direction to manufacture the tubular nonwoven fabric 12. In this case, in order to make it easier to pull out the cylindrical object in the axial direction of the second rotary body 9, the axial distance between the main rotary body and the sub rotary body is made smaller in the pull-out direction.

Further, as described above, the rotation diameters of the main rotary body and the sub rotary body may be reduced in the pull-out direction. In this case, both rotating bodies or only one may be used. FIG. 7 shows an embodiment example of a method for producing a tubular electretized nonwoven fabric using spunbond fibers. The polymer extruded from the spinneret 18 is stretched by an ejector 19 to form spunbond fibers 20 and collected on the first rotating body 6. At this time, the spunbond fibers 20 are collected in the DC electric field formed between the applying electrode 5 and the grounded first rotating body 6 to obtain the electretized web 8. At this time, it is preferable to bond with the heat roller 21 in order to assist the web formation. In addition, chemical bonding and hot melt bonding can also be used.

Thereafter, this web is transferred to the second rotating body 9, and an applied electric field is further formed between the main rotating body 24 and the sub rotating body 25, which are grounded to the application electrodes 22 and 23, to form an electret cylinder. Item 10 was created. In this case, the joining is strengthened by the third rotating body 13, and the tubular material 10 is sequentially pulled out in the axial direction to manufacture the tubular nonwoven fabric 12.

Regarding the method of forming the fiber to be conveyed, in addition to the melt blow method and the spun bond method, a flash spinning method, a method of conveying short fibers or long fibers while opening them with an air current, and a method for producing a fibrous material to be conveyed. If so, it is not limited at all.

The material of the carrier fiber is a synthetic organic polymer fiber,
Polyester fibers, fluorine fibers, olefin fibers, especially polypropylene and polystyrene fibers are preferred. Further, not only one-component fibers but also a mixture with other fibers can be used.
When a low melting point fiber is mixed with another fiber, a web or a tubular product can be easily formed. Further, short fibers, long fibers, a mixture with filaments, and a carrier fiber in which a thick fiber diameter and a thin fiber diameter are mixed can also be used.

The first rotating body 6 is preferably made of a porous material for passing or sucking the carrier fluid. Since the second rotating body 9 pulls out the electretized tubular body in the axial direction, it is preferable that the second rotating body 9 has a surface with low friction resistance. In particular, a satin surface, a polyfluorinated ethylene resin processed surface, and a mirror-finished surface are preferable. As the hot melt resin, a polyolefin copolymer resin, a polyester copolymer resin or the like can be used.

The density of the tubular nonwoven fabric can be changed by the collection distance of the conveyed fibers.

According to the method for producing a tubular non-woven fabric of the present invention, a tubular non-woven fabric having a large basis weight can be produced without the tubular non-woven fabric extending or breaking. Also, the diameter of the tubular nonwoven fabric can be freely changed.

The surface electrification density of the tubular electretized nonwoven fabric produced in this manner is 1 × 10 ^-10 coulomb / cm ² or more. More preferably, it is 3 × 10 ⁻¹⁰ coulomb / cm ² or more, and the upper limit is 1 × 10 ⁻⁸ coulomb / cm from the discharge limit according to the knowledge of the present inventors.
Around ² Also, the polarities of the front and back are different.

Here, in the method of measuring the surface charge density, as shown in FIG. 8, the sample 30 is placed on the ground electrode 26 and brought into contact with the measurement electrode 27 to induce charges in the capacitor 28.
This potential is measured by the electrometer 29 and calculated from the following formula.

Surface charge density (coulomb / cm ² ) = C × V / S C: capacitor capacity (coulomb) V: measured potential (volt) S: measured electrode area (3.14 cm ² ) Since the tubular electret non-woven fabric does not have a sewn portion, it is possible to prevent the electroadhesive property from being deteriorated by the sewing thread, increase the pressure loss due to the overlapping of the sewn section when used in a filter, and prevent dust leakage from the sewing thread.

Further, since there is no sewn portion, the mechanical strength can be improved. In addition, since the inner surface charges of the tubular electretized nonwoven fabric have the same polarity, mutual repulsion does not occur and they are not adsorbed and the opened state can be maintained and the handling is easy. When it is used for a filter, it can collect uniformly in the circumferential direction and is preferable. Therefore, it can be used in a wide range of fields such as bag filters, vacuum cleaner filters, copy filters, wipers, hair caps (dustproof hats), and masks.

[0032]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited thereto.

Example 1 Polypropylene was spun at a temperature of 265 ° C. by the method shown in FIG.
Melt-blow spinning was performed and the melt-blown fibers were collected by a first rotating body having a diameter of 20 cm in a DC electric field. 30K between the wire type electrode and the first rotating body
V was applied. The first rotating body was rotated at 20 rpm on a wire mesh net surface of 20 mesh to prepare an electretized web having an average basis weight of 5 g / m ^{2 with} a width of about 15 cm. 10 cm from the surface of the first rotating body
It moved to the separated 2nd rotating body of 32 cm in diameter, and formed the electretized cylinder.

The second rotating body has an inclination angle of 1 degree with respect to the horizontal axis in the longitudinal drawing direction on the matte surface. Further, in order to bond the webs on the second rotating body, the third rotating body heated with hot air was used. A trial was made without using the third rotating body, but the adhesiveness was inferior to the one using it. This cylindrical object is sequentially pulled out in the axial direction of the second rotating body to give a basis weight 8.
A cylindrical electretized nonwoven fabric having a circumference of 0 g / m ² and a circumference of 100 cm was produced.

The surface charge density of this non-woven fabric is surface −8 × 1.
It was 0 ⁻¹⁰ coulomb / cm ² , and the back surface was + 7 × 10 ⁻¹⁰ coulomb / cm ² . The filter performance was measured with polystyrene 0.3 micron particles and a measurement wind speed of 1.5 m / min, and as a result, a collection efficiency of 99.9 or higher was shown.

This tubular electretized nonwoven fabric is strong,
Since there were no sewn parts, the collection efficiency was good and it was the most suitable bag filter. It was also excellent as a wiper that was cut into two layers and had a good electric adsorption property.

Example 2 By the method shown in FIG. 7, polypropylene fiber and polypropylene copolymer fiber (melting point 125 ° C.) were mixed-spun and sucked with an ejector at 4500 m / min (average single yarn fineness 5 denier) and opened. The fibers were made to be fine and sprayed and collected on the first rotating body having a diameter of 20 cm. At this time, an electric field of 7 KV / cm was formed between the applied electrode and the grounded first rotating body to prepare an electretized web. Further, the first rotating body has a 20 mesh wire net surface and is provided with suction. The collected deposited electretized fibers were temporarily adhered to each other with a hot roll at 90 ° C. to obtain an electretized web having a width of about 15 cm and a weight per unit area of 6 g / m ² . This was transferred to the second rotating body, and an electric field of 6 KV / cm was further formed between the wire application electrode and the grounded sub-rotating body to manufacture an electretized tubular product. The second rotating body is composed of a main rotating body having a diameter of 20 cm and a sub rotating body having a diameter of 20 cm, and the distance between the centers of the two is 70 cm. The sub-rotating body was brought into contact with a third rotating body (hot embossing roll) at 100 ° C. to strengthen the adhesion of the tubular object. Pull out the formed cylindrical objects in order in the axial direction, and
A tubular electretized non-woven fabric having a circumference of 200 cm and a weight of 0 g / m ² was produced.

The surface charge density of this non-woven fabric is surface −7 ×
It was 10 ⁻¹⁰ coulomb / cm ² , and the back surface was 6 × 10 ⁻¹⁰ coulomb / cm ² .

As a large bag filter, this product was strong and had no sewn portion, so that it could collect dust uniformly and had excellent filter performance.

[Brief description of drawings]

FIG. 1 shows a tubular electret nonwoven fabric of the present invention.

FIG. 2 shows a state of electret fibers inside.

FIG. 3 is a schematic view of an embodiment of the manufacturing apparatus as seen from the axial direction of the rotating body.

FIG. 4 is a side view of that of FIG.

FIG. 5 shows a gradient of a rotation diameter of a second rotating body.

FIG. 6 shows a manufacturing method of an embodiment of the present invention in which the diameter of a tubular nonwoven fabric can be changed.

FIG. 7 shows an embodiment for producing a tubular electretized nonwoven fabric from fibers by a spunbond method.

FIG. 8 shows a method for measuring surface charge density.

[Explanation of symbols]

 1: Cylindrical electretized nonwoven fabric 2: Electretized fiber 3: Melt blow mouthpiece 4: Melt blown fiber 5: Applying electrode 6: Grounded first rotating body 7: DC high voltage generator 8: Electretized web 9: Second rotating body 10 : Electretized tubular material 11: Suction 12: Cylindrical electretized nonwoven fabric 13: Third rotating body 14: Take-up roller 15: Receiving box car 16: Main rotating body of second rotating body 17: Sub rotation of second rotating body Body 18: Spinneret 19: Ejector 20: Spunbond Fiber 21: Heat Roller 22: Applying Electrode 23: Applying Electrode 24: Main Rotating Body 25: Grounded Sub Rotating Body 26: Earthing Electrode 27: Measuring Electrode 28: Capacitor 29: Electrometer 30: Sample

Claims (14)

[Claims] 1. Surface charge density 1 × 10 ^-10 coulomb / cm
A tubular electretized non-woven fabric having ^two or more. 2. The tubular electret non-woven fabric according to claim 1, which is made of an olefinic material and has an inner surface and an outer surface having different polarities. 3. The tubular electret non-woven fabric according to claim 1, which is made of a melt blown non-woven fabric. 4. The tubular electret nonwoven fabric according to claim 1, which is made of a spunbonded nonwoven fabric. 5. The tubular electret non-woven fabric according to claim 4, which is made of a low melting point material and a high melting point material. 6. An electretized web is formed while collecting a fibrous material conveyed by a fluid on a first rotating body in a DC electric field, and then the web is moved from the first rotating body to a second rotating body. A tubular electret nonwoven fabric characterized by being moved to a rotary body, forming a tubular body by the web on the second rotary body, and drawing the formed tubular body in the axial direction of the second rotary body. Manufacturing method. 7. A web is formed while collecting a fibrous material conveyed by a fluid on the first rotating body, and then the web is moved from the first rotating body to the second rotating body. A direct current electric field is created between the application electrode and the second rotating body on the two rotating bodies to form a tubular body made of the electretized web, and then the tubular body is moved in the axial direction of the second rotating body. A method for producing a tubular electretized nonwoven fabric, which is characterized in that 8. An electretized web is formed while collecting a fibrous material conveyed by a fluid on a first rotating body in a DC electric field, and then the web is separated from the first rotating body by a first rotating body. When the cylindrical body made of the web is formed on the second rotating body by moving it to the two rotating bodies, a direct current electric field is further created between the applying electrode and the second rotating body to form the electretized cylindrical body. A method for producing a tubular electretized non-woven fabric, which is produced and drawn out in the axial direction of the second rotating body. 9. The method for producing a tubular electret nonwoven fabric according to claim 6, wherein the direct current electric field is formed by the first rotating body for the application electrode and the ground electrode. 10. The second rotating body comprises at least a main rotating body and a sub rotating body, and the diameter of the cylindrical object is changed by changing the interval between these rotating bodies. A method for manufacturing a tubular electret non-woven fabric. 11. The method for producing a tubular electret non-woven fabric according to claim 10, further comprising a device for joining the web to the first rotating body. 12. The method for producing a tubular electret nonwoven fabric according to claim 6, wherein a device for joining a tubular object to the second rotating body is provided. 13. A tubular electret according to claim 6, wherein the web or the tubular object is joined by bringing the third rotary body into contact with the first rotary body or the second rotary body, or both of them. Method of manufacturing non-woven fabric. 14. The tubular electret nonwoven fabric according to claim 7, wherein the diameter of the rotating body of the second rotating body is such that the diameter of the rotating body becomes smaller in the direction of pulling out the formed tubular object. Manufacturing method.