JPH06257064A - Production of electret sheet - Google Patents

Abstract

PURPOSE:To obtain an electret sheet free from the attenuation of the charge of an electret material and free from the lowering in its filter performance by laminating a preliminarily melted monofilament reinforcing material to the electret material and subsequently press-bonding both the laminated materials. CONSTITUTION:A monofilament reinforcing material comprising polyethylene or polypropylene is preliminarily melted or semi-melted, laminated to an electret material, and subsequently press-bonded through e.g. calender rolls to obtain a sheet material free from the attenuation of the charge of the electret material, giving good rigidity between electrets, thereby capable of resisting to secondary processings such as a ruffling treatment. The electret material is preferably 6 nonwoven fabric such as spun bond fabric comprising synthetic fibers such as polyethylene or polypropylene fibers, melt roll-spun fabric, dry or wet-made paper, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electret filter such as an air purifier filter, an OA equipment filter, a building air conditioner filter and a clean room filter, a wiper and a clothing material.

[0002]

2. Description of the Related Art Conventionally, glass fibers have been used for air filters.
Or synthetic fibers are used. As for the air filter made of synthetic fiber, there is also an electret filter in which a permanent charge is applied to the air filter in order to improve the performance. These have the problem of low rigidity, and secondary processing such as pleating has been difficult. As a method for solving this, for example, there is an electret filter disclosed in Japanese Patent Laid-Open No. 1-194912 and a method for manufacturing the same. Here, an electret filter in which an electretized nonwoven fabric and a mesh made of synthetic fibers are heat-sealed over the entire surface and a method for producing the same are disclosed. But,
In the manufacturing method, the electretized non-woven fabric and the net-like material are simultaneously passed through the embossing roll to be thermally fused, so that there is a problem that the electret charge of the non-woven fabric is attenuated or disappeared by the heat of the embossing roll. Further, since the surface of the non-woven fabric is also embossed for integration, there is a problem that that portion does not function as a filter.

Besides this, as disclosed in Japanese Utility Model Laid-Open No. 1-156715, there is also a method in which a filter is formed unevenly and a spacer is placed in the recessed portion. However, when the filter having the unevenness is pleated, there is a problem that large wrinkles occur at the top of the filter and uniform pleating cannot be performed.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for manufacturing an electret filter having rigidity sufficient to withstand secondary processing such as pleating without damaging or eliminating the electric charge of the electret material. It is a thing.

[0005]

The present invention is a method for producing an electret sheet comprising a monofilament reinforcing material and an electret material, in which the reinforcing material is previously melted or semi-molten, and then the reinforcing material is used. A method for manufacturing an electret sheet, which comprises a step of stacking and press-bonding an electret material.

According to the present invention, the heat fusion component of the monofilament reinforcing material is melted before the electret materials are laminated,
Alternatively, the point is that a step of attaching the electret material in a semi-molten state is added.

In the present invention, the heat for melting or semi-melting the monofilament reinforcing material is not applied to the electret material, so that the charge of the electret material can be prevented from being attenuated or disappeared. Further, since the electret material and the monofilament reinforcing material are sufficiently adhered to each other, it is possible to impart rigidity enough to withstand secondary processing such as fold processing.

The monofilament reinforcing material in the present invention is a monofilament or a net made of them, which is wholly composed of a homogeneous heat-sealing component or a part of which is composed of a heat-sealing component. When a part of the monofilament is composed of a heat-sealing component, a cross-sectional structure of a composite core of a sheath core type or a side-by-side type is used. Examples of the heat fusion component include polyethylene, polypropylene, ethylene vinyl acetate copolymer, polyester copolymer, polyamide copolymer and the like.

When the monofilament of the monofilament reinforcing material is a composite filament, the first component is a heat-fusible component and the other components are composed of components having a melting point higher than that of the first component. By making the melting points different in this way, it is possible to bond the first component with the electret material without being melted even if the first component is in a molten state. At this time, it is preferable that the melting point difference between the first component and the other component is 20 ° C. or more.

The monofilament of the monofilament reinforcing material has a diameter of 0.05 mm to 1.0 mm, and if the diameter is less than 0.05 mm, the rigidity is insufficient for crimping. If the diameter exceeds 1.0 mm, the rigidity will be too strong and the original shape will be restored even after pleating. A more preferable diameter range is 0.1 to 0.3 mm.

Examples of the electret material in the present invention include films, woven fabrics, and non-woven fabrics, and non-woven fabrics made of synthetic fibers are particularly preferable. Specifically, a span composed of polyethylene, polypropylene, polyethylene terephthalate, polystyrene, polycarbonate, poly-3-methyl-1-butene, poly-4-methyl-1-pentene, polyvinylidene fluoride, polytetramethylene fluoride, rayon, etc. Bond, melt blow spinning, dry papermaking,
It is a non-woven fabric of wet papermaking.

In the present invention, the electret sheet can be a product such as an air filter, a wiper, a material for clothes, etc., and can be subjected to secondary processing such as fold processing.

In the present invention, in order to make the monofilament reinforcing material in a molten or semi-molten state, there are a method of contacting with a hot plate and a method of passing it through a hot air oven without contact. In the former case, it is preferable to use a hot plate made of a fluororesin in order to prevent the heat fusion component from adhering to the contact portion.
The heating temperature is preferably set between the melting point of the heat-sealing component of the monofilament and the melting point of the other component.

In the present invention, in order to bond the monofilament reinforcing material and the electret material, which are heated to a molten or semi-molten state, there is a method in which the monofilament reinforcing material and the electret material are superposed and then pressure-bonded by a calender roll. At this time, the surface temperature of the calender roll is set below the melting point of the monofilament reinforcing material because the monofilament reinforcing material is in a molten or semi-molten state, but the charge of the electret material is attenuated,
Alternatively, from the viewpoint of preventing disappearance, it is preferable that the temperature is lower, and it may be room temperature.

In the present invention, in addition to the monofilament, a metal thin wire can be used at the same time to provide rigidity. As a result, the rigidity is increased and, at the same time, when the filter is used for a long time as a pleat filter, the pleat is hardly deformed.

[0016]

The electret sheet manufactured according to the present invention can prevent the electric charge from being attenuated or disappeared by heat, and at the same time, can have a rigidity enough to withstand secondary processing such as pleating.

[0017]

【Example】

Example 1 ^Two electret materials 3 prepared by electretizing a melt-blown non-woven fabric composed of polypropylene fibers having a diameter of 2.0 μm and a basis weight of 30 g / m ² are prepared, and a diameter of 0.3 mm, polyethylene and polypropylene are provided between the two electret materials 3. The monofilaments 4 having a sheath core structure are arranged at a pitch of 10 mm in the width direction, and as shown in FIG. 1, the monofilaments 4 are heated by a hot plate 2 whose surface is made of Teflon to melt polyethylene, which is a molten component, It was passed through a calendar roll 1 together with the electret material 3. At this time, the set temperature of the calender roll 1 is 80 ° C, and the set temperature of the hot plate 2 is 140 ° C. Obtained electret sheet 5
Example 1 and FIG. 3 shows a schematic view of the form of the electret sheet 5.

Comparative Example 1 Two pieces of the same electret material 3 as in Example 1 were prepared, and the same monofilament 4 as in Example 1 was arranged between the electret materials 3 in the same manner as in Example 1, and as shown in FIG. The sample of Comparative Example 1 was obtained by passing through a calendar roll 1 whose surface temperature was set at 130 ° C. The form of the electret sheet 5 of Comparative Example 1 was almost the same as that of Example 1.

Comparative Example 2 Two pieces of the same electret material 3 as in Example 1 were prepared, and the monofilament 4 used in Example 1 was replaced with the electret material 3.
The sample of Comparative Example 2 was obtained by passing it through a calender roll 1 having a surface temperature set to 80 ° C. as shown in FIG.

Comparative Example 3 Two samples of the same electret material 3 as in Example 1 were prepared and laminated without bonding them to obtain a sample of Comparative Example 3.
In Comparative Example 2, the monofilament was not melted at all by the calender roll, and there was no adhesion between the electret material and the monofilament, and the product was unsatisfactory. As a result of raising the temperature of the calender rolls until the adhesion occurred, the adhesion was carried out at 130 ° C. which was the same as in Comparative Example 1.

As a result of pleating the electret sheets produced in the steps of Example 1 and Comparative Example 1 with a folding width of 17 mm, both were able to be processed into a sharp V-shape.

The electret sheet produced in the steps of Example 1, Comparative Example 1 and Comparative Example 3 was subjected to a wind velocity of 2.5 cm / s and had a particle size of 0.10 μm.
The air dust collection efficiency of m to 0.15 μm was measured by a light scattering type particle counter (RION particle counter KC-14). The results are shown in Table 1.

[0023]

[Table 1]

From Table 1, in comparison with Comparative Example 1, Example 1
It can be seen that the atmospheric dust collection efficiency is large and almost the same as Comparative Example 3. This means that the electret material of Example 1 was provided with rigidity while losing almost no electric charge. On the other hand, in Comparative Example 1, heat is applied at the stage of adhering the monofilament, and the amount of electric charge is attenuated, so that the atmospheric dust collection efficiency is lower than that in Example 1 and Comparative Example 3.

[0025]

The present invention relates to a step of imparting rigidity to an electret material by using a monofilament reinforcing material containing a heat-sealing component, and it is possible to impart rigidity to an electret sheet without damaging the charge of the electret material.

[Brief description of drawings]

FIG. 1 is a schematic view showing one example of a manufacturing method of the present invention.

FIG. 2 is a schematic view of a manufacturing method which is one of comparative examples of the present invention.

FIG. 3 is a schematic view showing an example of an electret sheet obtained by an example.

[Explanation of symbols]

 1 Calender Roll 2 Teflon Hot Plate 3 Electret Material 4 Monofilament Reinforcement Material 5 Electret Sheet

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location D04H 1/72 A 7199-3B

Claims (1)

[Claims] 1. A method of manufacturing an electret sheet comprising a monofilament reinforcing material and an electret material, wherein a step of previously melting the reinforcing material or a semi-molten state is performed, and then the reinforcing material and the electret material are superposed and pressure-bonded. A method of manufacturing an electret sheet, comprising the steps of: