JPS61272063A - Mask - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a mask having good charge stability, low pressure loss, and high collection efficiency.

[Prior art] Conventionally, as a mask using electret,
The one proposed in Publication No. 9-124 is known. This is a method in which a high pressure is applied near a die for forming melt-blown fibers to convert IN to electret, thereby obtaining a sheet-like material.

In the fibrous sheet obtained by this method, the electret fibers are randomly dispersed to form a sheet-like material, so the orientation of polarized charges is random, and the mutual polarized charges weaken and cancel each other out within the sheet. This will cause inconvenience. In addition, the electric field strength is also weak, and the stability of the charge over time is also reduced.

[Problems to be Solved by the Invention] An object of the present invention is to provide a mask that has excellent charge stability, low pressure loss, and high collection efficiency, which is not found in such conventional electret masks. It is.

[Means for Solving the Problems] The present invention uses an electret fibrous sheet, which has a charge on its surface and whose activation energy of polarized charges constituting the charge is at least 0°2 eV, as at least the inner material. This mask is characterized by:

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a perspective view of an example of a mask according to the present invention, and FIG. 2 is a sectional view taken along line AA' in FIG. 1.

The mask 1 includes a mask body 2 made of a fibrous sheet and a string 3.
It consists of

The mask body 2 is composed of an inner material 4 made of an electret fibrous sheet and an outer material 5 covering the inner material 4. External material 5
Usually, fiber materials other than the inner material 4 are used, but there is no particular limitation.

In the mask of the present invention, the outer material 5 is used to increase the airflow rate to collect coarse dust, and the inner material 4 is an electret fibrous sheet with low pressure loss and good charge stability to collect fine dust. I have to.

FIG. 3 is a front view of another example of the mask according to the present invention, and FIG. 4 is a sectional view taken along line BB' in FIG. 3. In the mask 6 shown in FIGS. 3 and 4, the mask body 2 is provided with a fold structure. The pleats 7 stretch when the mask is worn to better fit the face and prevent side leakage from the sides.

Furthermore, the form of the mask is not limited to those shown in FIGS. 1 to 4, but a molded mask 8 as shown in FIG.
It can also be used in the form of This molded mask 8 has wide spaces between the 49 and the mouth 10, so it does not feel stuffy at all and has excellent shape retention.

In the present invention, having a charge on the surface means having a positive charge or a negative charge on the surface like a normal electret.

There is no limit to the amount of such charge in the present invention, but since it is too weak and may cause performance problems, the amount of polarized charge held within the fibrous sheet should be approximately 7X10-"C/atf or more. is preferably 2×10−10c10yt or more.

The fibrous sheet referred to in the present invention has an electrical resistivity of 1013
Any material having a resistance of Ω·cm or more can be used. For example, fibrous materials formed from synthetic resins such as polyolefin, polyester, polycarbonate, polyfluorine resin, and vinyl chloride resin, glass, and other inorganic compounds can be used. The above-mentioned fibrous form may be any form as long as a part thereof has a fibrous shape.

Furthermore, fibers coated with an organic compound having an electrical resistivity of 1013 Ω·cm or more, such as core-sheath type fibers, are also included.

The form of such a sheet-like material is not particularly limited, but a fabric-like material is selected from the viewpoint of flexibility and ease of design for various uses. Such fabrics include, for example, nonwoven fabrics, knitted fabrics, paper-like materials, and the like. Of course, it also includes fabrics in which at least a portion or one side of the fabric is made into a film, a fibrous porous film, a sponge-like sheet, and the like. The electrical resistivity of the rough sheet is 1013
Includes those processed with resin using organic compounds with a resistance of Ω・cm or more. Among these, those having a non-woven structure are preferred because they are easy to mold.

The charge possessed by the electret fibrous sheet of the present invention is
It is distinctive in that the polarized charges constituting it have an activation energy of at least 0°2 eV.

This activation energy can be found from the chart in Figure 7, which records the amount of current generated by depolarization of polarized charges depending on temperature, and this energy represents the depth of charge trapping in the electret. This has a large impact on the lifespan and durability of the electret.

Measurement of such activation energy (thermally stimulated current measurement)
As shown in FIG. 6, both sides of the electret fibrous sheet 13 placed in a heating tank 12 having a temperature control device 11 are strongly sandwiched between electrodes 14 and 15, and the electrodes and a high-sensitivity ammeter 16' are connected to each other. Connect and measure. That is,
When the temperature of the heating tank is raised at a constant heating rate, for example, 5° C./min from room temperature to around the melting point, the trapped charges are depolarized and a current flows. This current is transferred to the data processing device 17
When the current is recorded on the recorder 18, current curves for various temperature ranges are obtained (FIG. 7). The quotient obtained by dividing the area of this current curve by the area of the measurement sample is the amount of polarized charge (measurement area).

The rise of each peak in this chart follows the following formula, so for the rise of the peak, InJ vs. 1/T
The activation energy of the polarized charge can be calculated from the slope of the obtained straight line.

In J=C-△E/kT [In the formula, J: Depolarization current (A) C: Constant ΔE: Activation energy (eV) k: Portzmann constant T: Temperature (0K)] Activation energy is electric charge From the viewpoint of stability, it is important to have a current peak of at least 0.2 eV above room temperature.

In other words, the greater the activation energy value, the better the lifetime of the electret. This fact was brought about for the first time by the electret sheet of the present invention. For this reason, in the present invention, those having an activation energy of 0.5 eV or more, particularly preferably 0.7 eV or more exhibit excellent heat resistance and chemical resistance.

Furthermore, it is a fact brought about by the present invention that the higher the temperature range where the peak occurs, the better the life of the electret is, at least 40°C1 preferably 80°C.
``C or higher is superior in durability and stability.Most preferably, 130'C or higher is excellent.

The electrical performance of the electret sheet of the present invention is better when the amount of polarization charge is larger, and at least 7X 10-
11c/cJ, preferably 2×1O-10C/-
or more.

Most preferably, it is 5×10−”c10+f or more.

Another feature of the electret fibrous sheet used in the present invention is that the fibrous sheet has an electric field structure in which polarized charges 19 are oriented in one direction, as shown in FIGS. 8 and 9. . Specifically, the sheets have the same type of charge on the same side. In the present invention, the sheet may have different types of charges in the thickness direction as shown in FIG. 10.

Ordinary electret fibers as shown in FIG. 11, which do not have such an electric field structure, do not have the above-mentioned characteristic electrical properties of the present invention. This point will be explained with reference to FIG.

FIG. 12 schematically shows, by vector lines (arrows), the direction of electric power generated by polarized charges possessed by the electret fibers constituting the conventional electret sheet of FIG. 11. As is clear from this figure, the direction of polarization is random, and the electric field structure is such that the vector quantities are canceled out and reduced. For this reason, this type of electret cannot withstand long-term use, and tends to be extremely susceptible to the presence of chemicals and thermal stimulation.

On the other hand, as is clear from FIGS. 8 and 9, the electret fibrous sheet used in the present invention has an electric field structure in which polarized charges are oriented in one direction. This structural difference is the reason for exhibiting the above-mentioned durability and electrical properties.

The electret fibrous sheet used in the present invention has excellent characteristics when used alone, but by assembling and stacking a plurality of electret sheets, the electret fibrous sheet used in the present invention has a long life.
A product with high durability against external conditions can be obtained.

For example, FIG. 13 shows the vector line state of a structure in which three electret fibrous sheets used in the present invention are laminated, and the polarized charges 19 are oriented in the same direction. This is shown in the power vector line (arrow) diagram, but in such a structure, the types of charges on the stacked surfaces of the stacked sheets may be different from each other. For example, the first layer of sheets may be stacked so that the vector lines are in opposite directions, or the vector lines between the sheets may be in opposite directions. In the case of the Electret N male sheet used in the present invention, the above-mentioned improvement in durability is achieved in all cases. This point is also a big difference from conventional electret sheets.

The electret fibrous sheet used in the present invention can be produced, for example, by the method shown in FIG.

That is, the fibrous sheet 2 formed by a normal and appropriate method
0 is placed on a water electrode 21 having a specific resistance of 103 Ω·cm and set at an appropriate temperature. In this case, it is preferable to increase the contact area between the sheet 20 and the electrode 21. water electrode 2
A high voltage direct current is applied to the surface of the sheet on the opposite side of 1 using a needle electrode 22. Container 23 containing water for water electrode 21
uses metal materials.

The applied voltage varies depending on the type of material composing the sheet, its molecular structure, the thickness of the sheet, the shape of the needle electrodes, the distance between the electrodes, etc., but for example, when the distance between the electrodes is 3 cm, it is at least 10 KV, preferably at least 10 KV. 15 to 5 QKV, more preferably 25 to 40KV. The application time is usually 0.1 seconds or more, preferably 1.0 to 120 seconds.

In this case, it is preferable to apply a double-sided treatment method by applying negative high voltage to one side of the sheet and applying positive high voltage to the opposite side, since it is possible to obtain a sheet with a roughly high polarization charge, and also to achieve the present invention. It is easy to obtain a sheet with electrical properties.

Further, it is preferable that the sheet to be treated has a thickness of 80 g/m 2 or less, more preferably 50 Q/m 2 or less, since it is easier to achieve the object of the present invention. In particular, for the inner material used as a mask, it is preferable that the inner material is 50 g/Tn2 or less from the viewpoint of pressure loss. It is easier to increase the amount of polarization charge when the diameter of 1174M is thinner than when it is thicker, and it is preferably 20μ or less, more preferably 1
It is preferably 0 μ or less. When the apparent density of the sheet made of such fibers is 0.05 g/- or more, preferably 0.1 g/cyJ or more, the application efficiency can be increased, and the charge stability of the resulting electret can also be improved.

In addition to being used as the outer material of masks! The fi fiber material does not need to be electretized or may be electretized, but it is preferable to have a thicker constituent fineness and a lower apparent density than the inner material from the standpoint of reducing pressure loss. Although the material and form are not limited, the form is preferably a non-woven fabric or an Irn woven proboscis from the viewpoint of collection efficiency.

When used as a molded mask, thermoplastic materials such as polyolefin organic polymers (polypropylene, polyethylene), polyester, polyfluorine compounds, etc. are suitable for the inner and outer materials. In addition, a nonwoven fabric structure is preferable from the viewpoint of easy moldability.

[Example] Example 1 Fabric weight 180/m2, apparent density 0.13Q/c+tf, made of polypropylene fibers with an average fiber diameter of 3.5 μm
The melt-blown nonwoven fabric sheet was made into an electret using the apparatus shown in FIG. The temperature of the water electrode was 50°C, the distance between the needle electrodes was 3 cm, the applied voltage was -30, and the v1 treatment time was 5 Q SeC.

Next, this sheet was dried at room temperature, and the sheet was turned over and placed on the water electrode. From now on, the applied voltage was set to +20 V for 60 s.
EC treatment was applied.

The peak temperatures of the depolarization current of the obtained electret fibrous sheet were 92°C and 153°C, and the activation energies at the respective peaks were 0°55eV and 0.85eV.
It was V. The polarization charge amount of this sheet is 8.5x10
``At c10+f, the amount of polarization charge above 130℃ is 4.8X1
It was 0''C/-.

Using this electret fibrous sheet as the inner material of the mask,
A short rayon fiber nonwoven fabric having an average diameter of 15 μm, a basis weight of 20 g/m 2 , and an apparent density of 0.25 g/cot was used as the outer material.

The pressure loss of the external material is Q under the condition of passing wind speed of 3 m/min.
It was 4 mmaq. Note that the pressure loss of the inner material was 2.6 mmaq under the same conditions. A mask with an inner material and an outer material having a width of 13 cm and a height of 1 Q cm as shown in FIGS. 1 and 2 was prepared.

The performance of this mask was measured according to JIS-7851 (dust mask). The particles used were 0.3 μm polystyrene standard latex (polystyrene uniform latex particles manufactured by Dow Chemical Company, USA). In addition, the particle counter that measures the collection efficiency of the mask is a light scattering aerosol counter (newly manufactured by Hitachi: AN1).
05 type) was used.

As a result, the pressure loss of this mask was 3.2 mmaq,
The collection efficiency was 96.8%, showing excellent characteristics.

Example 2 Using the inner and outer materials used in Example 1, a mask with pleats as shown in FIG. 3-4 was produced.

The dimensions of the mask were 16 cm in width and 1 Q cm in length, the fold width of the folds was 1 cm, and three folds were provided in the vertical direction. The pressure loss of this mask was 3.4 mmaq, and the collection efficiency was 97.5%.

Example 3 An electret fibrous sheet similar to that used in Example 1 was used as the inner material, and the outer material had an average diameter of 21 μm and a basis weight of 20Q/
Masks were made by thermoforming using m2 polypropylene spunbond nonwoven fabric.

The pressure loss of this mask is 3. ammaq, collection efficiency is 93
．． It was 5%.

Comparative Example 1 A mask was made in the same manner as in Example 1, except that the non-electret polypropylene melt-blown nonwoven fabric used in Example 1 was used as the inner material.

The performance of this mask was a pressure loss of 3.2 mmaQ, which was the same value as Example 1, but the collection efficiency was 52.0%, which was significantly inferior.

[Effects of the Invention] Since the mask of the present invention uses an electret fibrous sheet with stable charge over a long period of time as an inner material, it can achieve high collection efficiency that cannot be obtained with conventional masks with low pressure loss. . Target collected materials include dust, bacteria, viruses,
Airborne particles such as pollen.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an example of the mask according to the present invention, FIG. 2 is a sectional view taken along the line A-A' in FIG. 1, and FIG. 3 is a perspective view of another example of the mask according to the present invention. Hail front view,
FIG. 4 is a sectional view taken along the line B-8' in FIG. 3, FIG. 5 is a sectional view of still another example of the mask according to the present invention, and FIG. FIG. 7 is a schematic diagram showing the depolarization current curve shown by the electret fibrous sheet of the present invention, and FIG. 8 is a schematic diagram showing the polarization charge state of the cross section of the electret fibrous sheet, which is an example of the present invention. 9 is a schematic diagram showing the power vector line (arrow) of the fiber in FIG. 8, and FIG. 10 is a schematic diagram showing the polarization charge state of a cross section in another example of the electret fibrous sheet of the present invention. Fig. 11 is a schematic diagram showing the polarization charge state of the fibers in the cross section of a conventional electret fiber sheet, Fig. 12 is a schematic diagram showing the power vector line of the fibers in Fig. 11, and Fig. 13 is a schematic diagram of the electret fiber sheet of the present invention. FIG. 14 is a schematic diagram showing the state of vector lines of a structure in which fibrous sheets are laminated in three layers, and FIG. 14 is a schematic cross-sectional diagram showing an example of the apparatus for manufacturing the electret fibrous sheet of the present invention. 1.6, 8: Mask 2: Mask body 4: Inner material 5: Outer material 7: Fold portion Patent applicant Toshi Co., Ltd. Figure 1 Figure 5 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11/T/1 4 1 -5 'h v: Figure 12 Figure 13

Claims (11)

[Claims] (1) A mask characterized in that an electret fibrous sheet having charges on its surface and in which the activation energy of the polarized charges constituting the charges is at least 0.2 eV is used as at least the inner material. (2) The mask according to claim (1), wherein the electret fibrous sheet is a nonwoven fabric. (3) The mask according to claim (1) or (2), wherein the electret fibrous sheet is a melt-blown nonwoven fabric. (4) The mask according to claim (1) or (2), wherein the electret fibrous sheet is an olefin nonwoven fabric. (5) The amount of polarization charge of the electret fibrous sheet is 7×
10^-^1^1C/cm^2 or more of the mask according to claim (1). (6) The depolarization temperature of the polarized charges of the electret fibrous sheet is at least 40°C or higher.
Mask described in section 1). (7) The mask according to claim (1), wherein the average fineness of the inner material is smaller than the average fineness of the outer material. (8) Activation energy of polarized charge of inner material is 0.2 eV
The mask according to claim (1), comprising a plurality of laminated electret fibrous sheets. (9) The mask according to claim (1), wherein the outer material is an electret fibrous sheet. (10) The mask according to claim (1), wherein both the inner material and the outer material have a pleated structure. (11) The mask according to claim (1), wherein the inner material is an electret fiber sheet of 50 g/m^2 or less.