JPH0361789B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a novel nonwoven fiber molded article using electret fibers and a method for producing the same.

In addition, in the present invention, the nonwoven fiber molded body is
A molded product is obtained by using a core structure having a specific shape as a base, and depositing nonwoven fibers on the surface of at least part of the shape of the core structure to match the surface shape of the core structure. That's what I say.

[Prior art] Conventional non-woven fiber molded bodies made using electret fibers are produced by first making an electret fiber non-woven sheet (non-woven fabric), and then wrapping this around the mold body of the molded body or by applying an appropriate process. Nonwoven fiber molded bodies were created by processing and attaching them later.

However, such a method has the disadvantage that the adhesion between the molding die and the electret fiber nonwoven sheet is poor, and gaps often occur, causing problems with the uniformity of the product. for example,
When the molded body is used as a filter, there is a drawback that dust leakage occurs.

[Problems to be Solved by the Invention] In view of the above-mentioned points, an object of the present invention is to provide a high-quality material that has good adhesion between the molding material and the electret nonwoven fibers and has substantially no gaps. The object of the present invention is to provide a nonwoven fiber molded article that is effective in exhibiting a high-quality and uniform structure, and a method for producing the same.

[Means for Solving the Problems] The present invention that achieves the above-mentioned object has the following configuration.

That is, the nonwoven fiber molded article of the present invention comprises a mold core structure in which at least the surface layer is formed of a material having a volume resistivity of 10 ¹⁰ Ω·cm or less, and electret fibers having polarized charges. and an electret fiber layer substantially covering at least a part of the surface of the mold core structure.

Furthermore, the method for producing a nonwoven fiber molded article of the present invention includes:
The transported fibers are transformed into electret fibers by guiding them into an electric field formed between an applied electrode and a grounded mold core structure whose surface portion is made of a material with a specific resistance of 10 ^{to 10} Ωcm or less. , a method for producing a nonwoven fiber molded body, further comprising depositing the electret fibers on at least a portion of the surface of the mold core structure.

[Function] As a result of intensive research to achieve the above-mentioned objects, the present invention has been developed, in particular, to improve the volume resistivity in an electric field.
We have found that it is effective to use a mold made of a material with a resistance of 10 ¹⁰ Ω・cm or less as an electrode, and to collect the electret fibers on the electrode surface of this mold. The nonwoven fiber molded article of the present invention and its manufacturing method will be explained in detail.

FIG. 1 is a schematic diagram illustrating one embodiment of the method for manufacturing a nonwoven fiber molded article of the present invention, in which a molten polymer 2 is injected from a melt blowing die 1 together with heated air 3 to form fibers, and the heated air is The fibers are transported by the transport fibers 4 to the application electrode 5.
The volume resistivity of a, 5b and ground is 10 ¹⁰ Ω・cm
The fibers are formed into electret fibers by being guided into an electric field formed between the electrode 6a made of the following mold core structure, and the fibers are further placed on at least a portion of the surface of the electrode made of the mold core structure. The nonwoven fiber molded article 7a according to the present invention is obtained by depositing the fibers on the fibers. In the above, the conveyance does not necessarily have to be carried out by air, but can be carried out by using other fluids. Note that 8 in the figure is a DC high pressure generator.

Here, in order to obtain a somewhat large and uniform nonwoven fiber molded article of the present invention, when depositing the above-mentioned electret fibers, the relative positional relationship between the part to be deposited on the mold core structure and the fiber deposition direction should be adjusted. It is also effective to deposit the material while making it vary two-dimensionally or three-dimensionally. For example, by depositing while rotating the mold core structure side, the two-dimensional or three-dimensional variation can be prevented. It is effective to let it accumulate while slowing down.

Furthermore, a suction pipe 9 is also inserted from inside the mold core structure.
By depositing the nonwoven fibers on the surface of the mold core structure while exhausting the carrier fluid through the fibers, the adhesion between the deposited nonwoven fibers and the mold core structure can be further improved.

An example of the model structure of the nonwoven fiber molded article of the present invention obtained as described above is, for example, a mold core structure for molding (mold electrode) with a volume resistivity of 10 ¹⁰ Ω・cm or less, as shown in FIG. 6a and a deposited electret nonwoven fiber layer 10, which is obtained by depositing the electret nonwoven fibers while rotating the electrode 6a.

Further, FIG. 2 shows an example of a mode in which the conveying fibers 4 are deposited on an electrode 6b consisting of a rotating rod-shaped mold core structure for molding, and a nonwoven fiber molded body 7b as shown in FIG. 4 is manufactured. In this example,
It consists of a mold core structure (mold) 6b having a volume resistivity of 10 ¹⁰ Ω·cm or less and an electret nonwoven fiber layer 10 as shown in FIG.

In the present invention, the electrode used as the application electrode is preferably a non-contact type electrode,
Needle-like or wire-type electrodes can be preferably used.

In the method of the present invention, a DC voltage applied to such an electrode,
For example, apply 5 to 100 KV. The distance between the application electrode and the grounded mold core structure electrode is 1 to 30 cm.
It is preferable to set it to about 3, more preferably 3
It is best to set it to around 15cm. If it is less than 1 cm, it is not preferable to obtain a uniform electret fiber due to the electric field, and if it is more than 30 cm, the electric field becomes weak and effective electrification becomes generally difficult.

In order to improve the grounding property of the grounded mold core structure electrode, at least the surface layer of the mold core structure is
It is preferable to form the surface layer with a material having a volume resistivity of 10 ¹⁰ Ω·cm or less, more preferably 10 ⁵ Ω·cm or less, and most preferably 10 ^-3 Ω·cm or less. good. For this reason, the surface layer can be coated with a conductive paint, plated with metal, or made of various metal materials or conductive materials.

In a well-formed nonwoven fiber molded article of the present invention, the surface charge density of the electret fiber layer deposited on the surface of the mold core structure is generally 1×10 ^-10 when measured by an electrostatic induction method. It exhibits a coulomb/cm ² or more, and therefore can exert an effective electrical effect on the outside world.

The material used for the molten polymer preferably has a volume resistivity of 10 ¹³ Ω·cm or more from the viewpoint of stability of electret performance. For example, polypropylene, polystyrene, polyethylene, polyester, polycarbonate, fluororesin, etc. can be preferably used.

Further, when carrying out the method of the present invention, the ambient temperature during application is preferably within a range from about 3/5 of the absolute temperature of the polymer melting point to approximately below the melting point. If the polymer temperature is too high, it is difficult to fully exhibit the electret properties, which is undesirable. If the polymer temperature is too low, the adhesion of the fibers to the mold core structure tends to decrease, which is not desirable. do not have.

The grounded mold core structure electrode can be moved three-dimensionally by moving around, rotating, vertically, or oscillating.
By causing dimensional movement, the electret fibers are deposited uniformly on the surface of the mold core structure, or by creating a density gradient as desired, or by creating more or less deposited layers. A nonwoven fiber molded body having the following morphology can be manufactured. Further, the positional relationship between the application electrode and the mold core structure electrode can be changed as appropriate from the viewpoint of electret properties.

The method of fiberizing the polymer can be as shown in Fig. 1, in which a heated fluid is jetted simultaneously with the polymer, or a method in which the polymer is spun from an orifice and then fiberized using an ejector. Alternatively, there are methods of melting the polymer with a solvent and injecting it with pressurized gas from an orifice to form fibers, which can be selected as appropriate.From the viewpoint of moldability, melt blowing, in which heated fluid is injected at the same time as the polymer, is suitable. The method is most preferable, and mixed fiber melt blowing in which other fibers are mixed into the melt blow fibers by airflow may also be used.

Furthermore, it is possible to improve the adhesion of the fibers to the surface of the mold core structure by suctioning fluid from the inner surface of the mold core structure, and this is an effective means especially when a large number of deposited fibers are present.

[Function] According to the present invention as described above, there is provided an electret nonwoven fiber molded article that has good adhesion between the molding material and the electret nonwoven fiber and exhibits a high-quality and uniform structure, and its production. A method is provided.

When the nonwoven fiber molded article made of the electret fibers obtained in this way is used in a liquid or gas filter unit, it is a unit that can exhibit substantially no dust leakage and uniform filter performance. Can be used as Moreover, a molded body having a density gradient can be used to improve filter life.

Further, a cotton swab-shaped molded body as shown in FIG. 2 can be used as a wiper to absorb dust in narrow spaces.

Furthermore, since the nonwoven fiber molded article of the present invention can exert an electrical effect on the outside, it can be used as a health promotion material, a therapeutic material, and as a cover material for preventing various types of dust. .

[Examples] Hereinafter, based on Examples, specific configurations of the present invention,
Explain the effects.

Example 1 On the surface of a mold core structure made of polypropylene and having a cylindrical shape with a net-shaped hole of 1 mm square on the surface and a shape with flanges on both ends of the cylinder,
A thin layer of conductive paint with a volume resistivity of 10 ³ Ω·cm was applied.

This mold core structure electrode is grounded, and the polypropylene meltblown fibers are introduced into the electric field created by the needle-shaped application electrode and the grounded core structure electrode on the cylindrical surface of the core structure electrode, and the polypropylene meltblown fibers are electrified. was deposited and processed according to the outline shown in Fig. 1.

At this time, the distance between the needle-like application electrode and the mold core structure electrode was 6 cm. Moreover, the applied voltage was negative 30KV. The grounded mold core structure electrode was configured to be moved three-dimensionally, and a uniform electret fiber layer was deposited on the surface layer with a basis weight of 150 g/m ² . The surface charge density of the electret fiber layer was 5×10 ⁻¹⁰ coulombs/cm ² .

When the nonwoven fiber molded product obtained as described above was used as a gas filter, it was found that the filter unit had low pressure loss and high collection ability, and had uniform performance without dust leakage. I was able to confirm.

Example 2 Using an aluminum tube with a diameter of 3 mm and a volume resistivity of 2 x 10 ^-5 Ω・cm, use this as a ground electrode and apply a positive voltage of 20 KV to the needle-shaped electrode at a distance of 6.
The polypropylene meltblown fibers are conveyed between the cm application electrode and the ground electrode, and the electret fibers are deposited on the tip of the aluminum tube.
The processing was carried out according to the outline shown in Figure 2. The surface charge density of this electret fiber layer is 3.1×
It was 10 ^-10 coulombs/ ^cm2 .

When the thus obtained nonwoven fiber molded article was used as a wiper rod to collect dust that had entered the gap, it had a high dust collecting ability and was able to collect dust effectively.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are schematic diagrams each illustrating an embodiment of the method for producing a nonwoven fiber molded article of the present invention. FIGS. 3 and 4 are schematic model diagrams showing one embodiment of the nonwoven fiber molded article of the present invention, and illustrate the molded articles obtained by the methods shown in FIGS. 1 and 2, respectively. be. 1: Melt blow nozzle, 2: Polymer, 3: Heated air, 4: Conveying fiber, 5a, 5b: Application electrode,
6a, 6b: mold core structure electrode, 7a, 7
b: nonwoven fiber molded body, 8: high pressure generator, 9: suction tube, 10: electret nonwoven fiber layer.

Claims (1)

[Scope of Claims] 1. A mold core structure having at least a surface layer formed of a material having a volume resistivity of 10 ¹⁰ Ω·cm or less, and a mold core comprising an electret fiber having a polarized charge. 1. A nonwoven fiber molded article comprising at least an electret nonwoven fiber layer substantially covering at least a part of the surface of the structure. 2. The nonwoven fiber molded article according to claim 1, wherein the electret nonwoven fiber layer has a surface charge density of 1×10 ⁻¹⁰ coulombs/cm ² or more. 3. The nonwoven fiber molded article according to claim 1, wherein the electret nonwoven fiber layer has a difference in fiber density within the layer. 4. The nonwoven fiber molded article according to claim 1, wherein the electret nonwoven fiber layer is made of meltblown fibers. 5. The nonwoven fiber molded article according to claim 1, which is used for liquid or gas filter applications. 6 The transported fibers are transformed into electret fibers by guiding them into an electric field formed between an applied electrode and a grounded mold core structure whose surface portion is made of a material with a specific resistance of 10 ¹⁰ Ω cm or less. A method for producing a nonwoven fiber molded article, which further comprises depositing the electret fibers on at least a portion of the surface of the mold core structure. 7. When depositing the electret fibers, the relative positional relationship between the part to be deposited on the mold core structure and the fiber deposition direction is varied two-dimensionally or three-dimensionally. A method for producing a nonwoven fiber molded article according to Scope 6. 8. The method for producing a nonwoven fiber molded article according to claim 6, wherein the transported fibers have a volume resistivity of 10 ¹³ Ω·cm or more. 9. The method for producing a nonwoven fiber molded article according to claim 6, characterized in that the fibers are transported using a fluid. 10. The method for producing a nonwoven fiber molded article according to claim 9, characterized in that when depositing the electret fibers, the fibers are deposited while sucking a carrier fluid from inside the mold core structure. 11. The method for producing a nonwoven fiber molded article according to claim 9, wherein the fibers conveyed by the fluid are fibers formed by melt blow spinning.