JP2002249963A - Charged nonwoven - Google Patents

Abstract

An object of the present invention is to obtain a charged nonwoven fabric having better charging performance and improved initial collection efficiency, and desirably, when used continuously. An object of the present invention is to obtain a charged nonwoven fabric capable of maintaining high collection efficiency. The present invention relates to a charged nonwoven fabric including an acrylic fiber and a polyolefin fiber containing a phosphorus additive and a sulfur additive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a charged nonwoven fabric used for a filter, a mask, and the like.

[0002]

2. Description of the Related Art It is well known that various air filtering materials are used to collect dust in the air.
It is desired that such an air filtration material has a low pressure loss and a dust collection efficiency as high as possible, and various techniques have been proposed. Among them, the phenomenon that different fiber components are charged by friction has been known for a long time, and the friction between fibers generated during the preparation of a fiber web is utilized without increasing the apparent density of the fibers, which leads to an increase in pressure loss. Attention has been paid to a technology that can improve the collection efficiency by the electrification. Various combinations have been proposed as electrified nonwoven fabrics utilizing such friction by selecting fiber components involved in friction. As one example, U.S. Pat. No. 4,798,850 discloses that a clean polyolefin-based fiber and a clean acrylic-based fiber are formed as a fiber web by a card machine, and the friction between the fibers is used by utilizing the friction between the fibers. A technique for obtaining a nonwoven fabric is disclosed. In the specification of this application, surface treatment agents and oligomers that prevent electrification such as lubricants and antistatic agents adhering to the fiber surface were washed and removed with warm water, nonionic surfactants, alkaline aqueous solutions, alcohols, and the like. The state of the fiber is called "clean". This U.S. Pat.
No. 8,850, discloses a polyolefin fiber having a structure in which a part of hydrocarbons constituting polyethylene resin, ethylene-propylene copolymer or polypropylene resin is partially substituted with a cyano group or a halogen such as fluorine or chlorine. Things are listed. Further, as an acrylic fiber, a modacrylic fiber obtained by copolymerizing acrylonitrile with vinyl chloride or vinylidene chloride is disclosed.

Further, Japanese Patent Application Laid-Open No. Hei 7-256024 discloses that the above-mentioned polyolefin fiber is a composite fiber in which a polypropylene resin and a polyethylene resin are arranged in a core-sheath type or a side-by-side type, and the acrylic fiber is halogen-free polyacrylonitrile. An air filtration material is disclosed which is capable of frictionally charging these two types of fibers as fibers, and having the heat fusibility by the composite fibers.

[0004]

As described above, as a conventionally known charged nonwoven fabric, a combination of a polyolefin fiber and an acrylic fiber is disclosed in US Pat.
Japanese Patent Application Laid-Open No. 798,850 discloses a combination of a polyolefin fiber partially substituted with a cyano group or a halogen and modacrylic fiber, and Japanese Patent Application Laid-Open No. Hei 7-256024 discloses a material made of polypropylene / polyethylene in consideration of heat molding and the like. A combination of a heat-fusible polyolefin fiber and a halogen-free acrylic fiber is disclosed, but a charged nonwoven fabric having a low pressure loss and improved charging performance and excellent collection efficiency is desired. I was

[0005] In addition, when collecting dust supplied in a fixed amount using a charged nonwoven fabric, the change over time is measured by taking the collection efficiency on the vertical axis and the time (or dust supply amount) on the horizontal axis. At a relatively early stage, the charge is gradually neutralized, so that the collection efficiency is reduced. When the measurement is further continued, the non-woven fabric is clogged by dust collected in the charged non-woven fabric, and the apparent collection efficiency tends to increase.
The improvement of the collection efficiency due to the clogging is also called mechanical filtration, and involves an increase in pressure loss. Such a series of phenomena is called a bottom-down phenomenon from the shape of the collection efficiency curve. . In the field of filters and masks,
There has been a demand for a charged nonwoven fabric that does not cause a reduction in collection efficiency in this bottom-down phenomenon as much as possible.

As a result of various studies, the present inventors have found that
The charging performance is improved by using polyolefin-based fibers using a combination of specific additives, and a higher initial collection efficiency is obtained compared to a charged nonwoven fabric using a polyolefin-based fiber that does not use these additives. The present inventors have found that a charged nonwoven fabric having the same can be obtained and completed the invention of this application.
In addition, the inventors of the present application have found a charged nonwoven fabric capable of preventing a decrease in the collection efficiency in the above-described bottom-down phenomenon and maintaining a high collection efficiency by setting the amount of the specific additive to a certain amount or more. Completed the invention. Accordingly, an object of the present invention is to obtain a charged nonwoven fabric having an improved initial collection efficiency having better charging performance when other filter conditions are the same, and desirably a high nonwoven fabric when continuously used. An object of the present invention is to obtain a charged nonwoven fabric capable of maintaining collection efficiency.

[0007]

In order to achieve this object, according to the structure of the charged nonwoven fabric of the present invention, a polyolefin fiber containing an acrylic fiber, a phosphorus additive and a sulfur additive is used. And is characterized by including. Further, the charged nonwoven fabric of the present invention is preferably characterized in that the proportion of the phosphorus-based additive in the polyolefin-based fiber is 0.2% by weight or more.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. As described above, the feature of the present invention is a charged nonwoven fabric combining a polyolefin-based fiber and an acrylic-based fiber, wherein the polyolefin-based fiber contains a phosphorus-based additive and a sulfur-based additive. is there.

The resin forming the polyolefin fiber used in the present invention includes a polypropylene resin, a polyethylene resin, a polystyrene resin, a vinyl acetate copolymer resin, an ethylene-propylene copolymer, or a part of these resins. It is possible to use one or a combination of a plurality of resins substituted with a group or halogen, or a combination of composite resins. Further, for example, in a core-sheath type composite fiber, a resin other than the polyolefin resin may be used as the core component, and the above-mentioned polyolefin resin may be provided on the fiber surface as the sheath component. Particularly, preferred resins are polypropylene resin and polyethylene resin.

The polyolefin fiber used in the present invention contains a phosphorus additive and a sulfur additive. Even if the addition amount of the phosphorus-based additive alone is increased,
Although the obtained non-woven fabric does not improve the initial collection efficiency to a certain level or more, the initial collection efficiency is improved by using a polyolefin fiber combined with a sulfur additive. The polyolefin-based fiber may further contain other additives such as a phenol-based additive and an amine-based additive in addition to the phosphorus-based additive and the sulfur-based additive. In addition, 0.01% by weight of a phosphorus-based additive is contained in the polyolefin-based fiber.
It is desirable that the content be contained in the above range. In particular, when the content is 0.2% by weight or more, a so-called bottom-down phenomenon hardly occurs in the obtained charged nonwoven fabric, and a decrease in collection efficiency can be prevented.

The above-mentioned phosphorus-based additives include trisnonylphenyl phosphite, tris (2,4-di-t-butylphenyl) phosphite, distearylpentaerythritol diphosphite, bis (2,4-di-t-t -Butylphenyl) pentaerythritol phosphite, bis (2,6, di-t-butyl-4-methylphenyl) pentaerythritol phosphite, 2,2-methylenebis (4,6-di-t-butylphenyl) octylphos Fight, tetrakis (2,4-di-t-butylphenyl)
-4,4'-biphenylene-di-phosphonite, bis (2,4-bis (1,1-dimethylethyl) -6-methylphenyl) ethyl ester phosphite, tetrakis (2,4-di-t-butyl) Phosphorus antioxidants such as phenyl) (1,1-biphenyl) -4,4′-diylbisphosphonite and bis (bis (2,4-di-t-butyl-5-methylphenoxy) phosphino) Can be suitably used.

[0012] When the phosphorus-based additive is contained in the polyolefin-based fiber in an amount of 0.2% by weight or more, the collection efficiency tends to be hardly reduced due to the reduction of the charging ability due to the collection of particles. This is good because the lowest collection efficiency in the bottom-down phenomenon is increased. Since this tendency becomes more remarkable as the amount of the phosphorus-based additive increases, the phosphorus-based additive is preferably contained in the polyolefin-based fiber in an amount of 0.3% by weight or more, more preferably 0.6% by weight. % Should be included. However, if too much additive is contained, the spinnability of the fiber deteriorates. Therefore, the total amount of the phosphorus-based additive and the sulfur-based additive should not exceed 5% by weight, preferably 2% by weight or less. Preferably, it is 1% by weight or less.

The polyolefin fiber used in the present invention contains a sulfur additive in addition to the phosphorus additive. As the sulfur-based additive, dilauryl-3,
3'-thiodipropionate, dimyristyl-3,3 '
Sulfur-based antioxidants such as -thiodipropionate, distearyl-3,3'-thiodipropionate and pentaerythritol tetrakis can be suitably used. When the sulfur-based additive coexists with the phosphorus-based additive, the initial collection efficiency of the obtained charged nonwoven fabric is improved as compared with the case where only the phosphorus-based additive is used. The sulfur-based additive is desirably contained in the polyolefin-based fiber in an amount of 0.01% by weight or more, and when contained in an amount of 0.1% by weight or more, it is preferable because the initial collection efficiency is further improved.

The acrylic fiber used in the present invention is not particularly limited, and it is possible to use modacrylic or polyacrylonitrile alone or in combination as a composite fiber. Of these, polyacrylonitrile-based acrylic fibers spun using inorganic solvents such as nitric acid, aqueous zinc chloride, aqueous calcium chloride, and aqueous solutions of rhodanate (sodium thiocyanate, potassium thiocyanate, calcium thiocyanate) are used. In addition, it is possible to obtain a charged nonwoven fabric which suppresses a reduction in charging ability and hardly causes a reduction in collection efficiency.

Commercially available acrylic fibers spun with these inorganic solvents include "Vethron" (trade name, manufactured by Toho Rayon Co., Ltd.), "Cashmilon" (trade name, manufactured by Asahi Kasei Kogyo Co., Ltd.), and "EXLAN""(Nippon Exlan Industrial Co., Ltd., trade name)," Creslan "(Amer, USA)
ican Cyanamid Co. Product name),
“Zefran” (The Dow Chemical, USA)
Co. Made, brand name), "Cotel" (Courta, UK)
ulds Co. Product name). It is not clear why the use of acrylic fibers spun with these inorganic solvents suppresses a decrease in charging ability and makes it difficult to cause a decrease in collection efficiency. However, most of the polyacrylonitrile-based fibers spun and prepared with modacrylic fibers and organic solvents have a constricted irregular cross-section, and most of the polyacrylonitrile-based fibers spun and prepared with the above-mentioned inorganic solvents have a substantially circular cross section. Therefore, it is considered that the substantially circular cross section of the fiber has an advantageous effect on the charged state after frictional charging.

In the present invention, the weight mixing ratio between the polyolefin fiber and the acrylic fiber is preferably in the range of 30:70 to 80:20 in order to secure charging efficiency by friction. The charged nonwoven fabric of the present invention is
It is preferable to use only the polyolefin-based fiber and the acrylic-based fiber, but the present invention is not limited to this. The fiber component composed of the other resin may have a weight ratio of about 30% by weight or less in the charged nonwoven fabric. If so, substantially the same effect can be expected.

The residual amount of the above-mentioned surface treating agent in the fiber component, that is, 30 to 80 ° C.
The fiber that has been washed and dried at 80 ° C. for a minute is reduced in weight by washing and extracting again with methanol, and the weight of the fiber before the extraction with alcohol such as methanol is 0.2% by weight or less, preferably 0.2% by weight or less. It is preferable that the content be 0.15% by weight or less. The amount of residue in fibers washed with warm water or the like indicates the degree of fiber cleaning.

The charged nonwoven fabric may be reinforced with another nonwoven fabric such as a spunbonded nonwoven fabric or a reinforcing material such as a net, a woven fabric, or a knit. In the manufacturing process of the charged nonwoven fabric, the reinforcing material is laminated with a fibrous web charged in a web forming process or the like, and integrated by an entanglement means such as a needle punch or an adhesion means. By being integrated with the reinforcing material, the form stability of the charged nonwoven fabric in the subsequent process increases,
The strength of the obtained charged nonwoven fabric is also improved, and handling becomes easy. In particular, it is preferable to use a reinforcing material which has a low pressure loss and a high strength, and a reinforcing material which does not adhere to a fiber oil agent or the like is more preferable because the collection efficiency is less likely to decrease with time.

Hereinafter, a manufacturing process suitable for obtaining the charged nonwoven fabric of the present invention will be described by way of example. First, a plurality of fiber components including the above-described combination are spread and mixed at a predetermined weight mixing ratio, and then these fiber components are washed and cleaned with warm water or the like. Thereafter, the fibers are passed through a known web forming apparatus, and the fiber components are rubbed against each other to form a charged fiber web. The term "web forming apparatus" used herein refers to a card machine typified by a flat card or a roller card capable of rubbing and charging fiber components, as well as a garnet machine or an apparatus belonging to the air lay method. As an apparatus belonging to the air-lay method, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 5-9813 by the applicant of the present application, a plurality of opening cylinders are housed in a housing, and these cylinders are rotated at a high speed to form cylinders. There is a device capable of positively generating an air flow on the periphery and blowing the fiber component in a predetermined direction by the air flow. In particular, in the web formation by the air lay method, since the energy for rubbing the fibers in the process of positively generating the air flow is large, a better charged state can be realized as compared with a card machine or the like.

The fibrous web obtained by such a web forming apparatus can be used as it is as a charged nonwoven fabric. However, in order to mainly increase the strength of the web and to achieve auxiliary triboelectric charging, a needle punch method, a water jet method and the like are used. It is preferable to perform fiber entanglement by an entanglement method or the like.

Further, at the time of this entanglement, even if another nonwoven fabric such as a spunbonded nonwoven fabric, or a reinforcing material such as a net, a woven fabric or a knitted fabric is laminated with the fiber web or inserted into the fiber web and entangled. good. By reinforcing with a reinforcing material, the stability of the process can be obtained, and the strength of the obtained charged nonwoven fabric can be improved, resulting in excellent handling properties.

Since the charged non-woven fabric of the present invention is charged during the production of the fiber web, there are few design restrictions for realizing efficient charging such as corona discharge treatment.
It can be manufactured with an areal density and thickness according to the application.
However, the surface density is preferably 40 g / m ² or more in order to secure the web strength, and more preferably 150 g / m ² or more in order to use the mechanical filtration described above.

[0023]

Embodiments of the present invention will be described below. In this embodiment, specific numerical conditions and the like are illustrated in order to facilitate understanding of the present invention. However, the present invention is not limited only to these specific conditions.
Any suitable design changes and modifications can be made within the scope of the present invention.

In the embodiment of the present invention, the acrylic fiber is trade name "Vethron W241B" (manufactured by Toho Rayon Co., Ltd., fineness: 2.2 dtex, fiber length: 51 mm).
Polyacrylonitrile fibers prepared by spinning with an inorganic solvent are used. On the other hand, the sulfur-based antioxidant "Yoshinox DM" is used as a polyolefin-based fiber in the composition shown in Table 1.
TP (Dimyristyl-3,3′-thiodipropionate, manufactured by Yoshitomi Pharmaceutical Co., Ltd.) and a phosphorus antioxidant “Irgaf
os168 "(manufactured by Ciba-Geigy Co., Ltd., Tris (2, 4
-Di-t-butylphenyl) phosphite) (a fineness of 2.2 decitex and a fiber length of 5).
1 mm). Each fiber was mixed so that the weight mixing ratio was polyolefin-based fiber / acrylic fiber = 40/60, and then the fiber was cleaned with warm water. The cleaned fiber was separately confirmed by a methanol extraction method to have a surface treatment agent or the like remaining on the fiber of 0.15% by weight or less. These mixed and cleaned fibers are formed into a web by using a carding machine or an air laying machine, and entangled by a needle punch method under a condition of a needle density of 50 fibers / cm ² to obtain an area density of 130 g / m ² . A charged nonwoven fabric was produced.

[0025]

Table 1 Content of sulfur-based antioxidant Content of phosphorus-based antioxidant Example 1 0.2% by weight 0.7% by weight Example 2 0.2% by weight 0.1% by weight Comparative example 10% by weight 0.1% by weight Comparative Example 2 0% by weight 0.7% by weight

Next, a method for evaluating these charged nonwoven fabrics will be described. In this embodiment, as an example of a measuring method for evaluating the initial collection efficiency and the bottom-down improvement effect, the article 6 of “Standards of dust masks” (Ministry of Labor Notification No. 19 of 1988) applied to dust masks. The test was performed according to the test method described. First, the passing area of the dust has a diameter of 8
Each charged nonwoven fabric is cut into a predetermined shape so as to have a circular shape of 5 mm to obtain a measurement sample, which is attached to a prescribed measuring device.
Next, using quartz having a particle size of 2 μm or less as dust, the dust concentration is 30 ± 5 mg / m ³ , and the flow rate is 30 liter / min (0.03 m ³ / min), and the dust is supplied from the upstream side of the measurement sample. The amount of dust on the upstream side of the measurement sample and on the downstream side of the measurement sample was measured with a light scattering type dust concentration meter. This measurement result is the collection efficiency obtained by dividing the difference between the amount of dust supplied and the amount of dust observed downstream (the amount of dust repaired) by the amount of dust supplied and expressed as a percentage. (%) Was recorded over time. Further, the pressure loss at each measurement point was obtained by measuring and recording the pressure difference between the upstream side and the downstream side of the measurement sample using a manometer. These results will be described with reference to the drawings.

FIGS. 1 to 4 show four kinds of charged nonwoven fabrics according to Examples 1 and 2 and Comparative Examples 1 and 2 as measurement samples.
Dust supply amount for each measurement sample is 100mg in total
5 is a collection efficiency curve in which the collection efficiency when the measurement is performed up to is plotted. The vertical axis indicates the collection efficiency (%), and the horizontal axis indicates the dust supply amount (mg) from the start of measurement.

First, as shown in FIG. 1, the charged nonwoven fabric of Example 1 had an initial collection efficiency at the start of measurement of about 85%, which was nearly 20% higher than that of Comparative Example 2 described later. The minimum value of the collection efficiency is about 66% when the dust supply amount is 50 mg.
Thus, the amount of dust collected before reaching the minimum value was larger than that of each of the comparative examples, and the minimum value of the collection efficiency was higher than that of each of the comparative examples, indicating excellent dust collecting ability.

Further, as shown in FIG. 2, the charged nonwoven fabric of Example 2 had an initial collection efficiency at the start of measurement of about 79%, which was higher than that of Comparative Example 2 in which the total amount of additives was twice or more. . Further, the minimum value of the collection efficiency is about 53% when the dust supply amount is 50 mg, the amount of the dust collected before reaching the minimum value is larger than that of each comparative example, and the minimum value of the collection efficiency is phosphorus. Although there is a difference from Example 1 in which the content of the system additive is high,
It was comparable to Comparative Example 2 in which the amount of the additive was large, and was superior to Comparative Example 1.

As shown in FIG. 3, the charged nonwoven fabric of Comparative Example 1 had a low initial collection efficiency at the start of measurement of about 66%, and the minimum collection efficiency was about 45% when the dust supply amount was 40 mg. %, The amount of dust collected before reaching the minimum value was smaller than that of each example, and the minimum value of the collection efficiency was low, and the collection ability was inferior.

Although the charged nonwoven fabric of Comparative Example 2 contained seven times the amount of the phosphorus-based additive as compared with Comparative Example 1, as shown in FIG. The efficiency was as low as about 68%, and the minimum value of the collection efficiency was about 53% when the dust supply amount was 35 mg, and the amount of dust collected until reaching the minimum value was smaller than that of each example.

As can be understood from these results, in a charged nonwoven fabric composed of a combination of clean polyolefin fibers and clean acrylic fibers, a phosphorus-based additive comprising a phosphoric acid-based antioxidant in the polyolefin fibers. And the sulfur-containing additive composed of a sulfur-based antioxidant in the embodiment, a high initial collection efficiency was obtained,
The amount of dust that can be collected before reaching the minimum value of the collection efficiency due to the bottom-down phenomenon is large, and the dust collecting ability is excellent.

Further, in Example 1, in which the amount of the phosphorus-based additive composed of a phosphoric acid-based antioxidant is relatively large, the minimum value of the collection efficiency is higher than in Example 2, and the bottom due to the collection of dust is lower. It can be understood that the non-woven fabric is an excellent non-woven fabric which does not easily cause a down phenomenon and can maintain a high collection efficiency for a long period of time.

When the initial pressure losses of these four types of charged nonwoven fabrics were measured, all of them showed the same level of pressure loss.

Although the embodiments of the present invention have been described above with reference to the evaluation method of dust masks, the technology of the present invention is not limited to such applications and is generally applied to air filtration materials. Can be. When the charged nonwoven fabric of the present invention is used as a filtering material, it can be used alone or in combination with another filtering material. Further, it can be used for wiping cloths and the like utilizing the excellent charging characteristics of the charged nonwoven fabric of the present invention.

[0036]

The charged nonwoven fabric of the present invention contains an acrylic fiber and a polyolefin fiber containing a phosphorus additive and a sulfur additive, so that an excellent charged state can be realized. It has a high initial collection efficiency, a large amount of dust that can be collected up to the minimum value of the collection efficiency due to the bottom-down phenomenon, and has an excellent collection ability. Therefore, various air filtration materials having excellent filtration performance can be provided by applying the present invention.

In particular, by incorporating a phosphorus-based additive in an amount of 0.2% by weight or more based on the weight of the fiber, the lowering of the charged state is suppressed, so that the bottom-down phenomenon is improved. It is possible to provide a charged nonwoven fabric having an excellent charge state, which can maintain efficiency.

[Brief description of the drawings]

FIG. 1 is a characteristic curve diagram for explaining an evaluation test result regarding Example 1.

FIG. 2 is a characteristic curve diagram for explaining an evaluation test result of Example 2.

FIG. 3 is a characteristic curve diagram for explaining an evaluation test result for Comparative Example 1.

FIG. 4 is a characteristic curve diagram for explaining an evaluation test result regarding Comparative Example 2.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mihiro Suzuki 7th Kitatone, Sowa-cho, Sarushima-gun, Ibaraki Prefecture Within Nihon Vilene Co., Ltd. (72) Inventor Shigeki Hayashi 1 Shiojima, Fukuhara-cho, Fukuhara-cho, Koriyama-shi, Fukushima Prefecture −10 Inside Ube Nitto Kasei Co., Ltd. EE13 FF05 JJ22 JJ25 LA01 4L047 AA14 AA17 AA28 AA29 BA03 BA07 CB10 CC03 CC12 EA02

Claims (5)

[Claims] 1. A charged nonwoven fabric comprising an acrylic fiber and a polyolefin fiber containing a phosphorus-based additive and a sulfur-based additive. 2. The amount of the phosphorus-based additive is 0.2% based on the weight of the fiber.
The charged nonwoven fabric according to claim 1, wherein the content of the charged nonwoven fabric is not less than% by weight. 3. The sulfur-based additive is added in an amount of 0.1 to the weight of the fiber.
The charged nonwoven fabric according to claim 1, wherein the content is 1% by weight or more. 4. The charged nonwoven fabric according to claim 1, which is reinforced by a reinforcing material. 5. The charged nonwoven fabric according to claim 1, wherein the fibers are clean.