阅读说明：本技术 长纤维无纺布和使用该长纤维无纺布的过滤器增强材料 (Long fiber nonwoven fabric and filter reinforcing material using same ) 是由 吉田英夫 胜木千晶 西条正大 于 2019-03-18 设计创作，主要内容包括：该长纤维无纺布由双折射率(Δn)为0.005至0.020、结晶度为25％以下并且平均纤维直径为30μm至60μm的纤维组成,并且所述长纤维无纺布的单位面积的质量为50g/m<Sup>2</Sup>至120g/m<Sup>2</Sup>,并且在80℃、5.2kPa的压力下压制10秒的折叠角为15°以下。这种构造得到了适用于过滤器增强材料的打褶性以及满足褶形式保持性能的刚性。(The long fiber nonwoven fabric is composed of fibers having a birefringence (DELTA n) of 0.005 to 0.020, a crystallinity of 25% or less, and an average fiber diameter of 30 to 60 [ mu ] m, and has a mass per unit area of 50g/m 2 To 120g/m 2 And a folding angle of 15 DEG or less when pressed at 80 ℃ under a pressure of 5.2kPa for 10 seconds. This configuration results in pleatability suitable for the filter reinforcing material and rigidity satisfying the pleat form retention performance.)

1. A long-fiber nonwoven fabric comprising fibers having a birefringence (Δ n) of 0.005 or more and 0.020 or less, a crystallinity of 25% or less and an average fiber diameter of 30 μm or more and 60 μm or less, the long-fiber nonwoven fabric having a basis weight of 50g/m or more²And is less than or equal to 120g/m²And a folding angle after pressing at 80 ℃ for 10 seconds under a pressure of 5.2kPa is 15 DEG or less.

2. The long-fiber nonwoven fabric according to claim 1, wherein an average value of aspect ratios of fiber cross sections of the fibers constituting the long-fiber nonwoven fabric is greater than or equal to 1.05 and less than or equal to 1.2.

3. The long-fiber nonwoven fabric according to claim 1 or 2, wherein the fibers constituting the long-fiber nonwoven fabric are single fibers made of a resin containing polyethylene terephthalate as a main component and 0.02 mass% or more and 5 mass% or less of a thermoplastic polystyrene-based copolymer mixed with the polyethylene terephthalate.

4. The long-fiber nonwoven fabric according to claim 4, wherein the glass transition point temperature of the thermoplastic polystyrene-based copolymer is 100 ℃ or higher and 160 ℃ or lower.

5. A filter reinforcing material using the long fiber nonwoven fabric according to any one of claims 1 to 4.

Technical Field

The present invention relates to a filament nonwoven fabric suitable for a filter reinforcing material and a filter reinforcing material using the filament nonwoven fabric.

Background

Polyethylene terephthalate long fiber nonwoven fabrics have good dynamic physical properties, as well as air and water permeability, and are used in a variety of applications. However, when a polyethylene terephthalate long fiber nonwoven fabric is used as a material for a molded body, it is difficult for the fabric to conform to a mold such as an uneven mold in a wide temperature range and to be molded in various shapes.

In an air cleaner or a cabin of an automobile, a pleated filter (pleated filter) is generally used to improve dust removal performance, smoke removal performance, and the like. When a nonwoven fabric is used as the reinforcing material for a filter, the nonwoven fabric used needs to have a property of being capable of being pleated to have an arbitrary number of pleats and an arbitrary pitch between pleats. In addition, the filter needs to have rigidity with pleat shape retention properties to avoid contact or close contact between pleats when the filter is actually used as a filter unit containing stacked adsorbents such as activated carbon, and the nonwoven fabric as a reinforcing material also needs to have rigidity.

As nonwoven fabrics used as a filter reinforcing material, there have been proposed a short fiber nonwoven fabric using a polyethylene terephthalate-based core-sheath composite fiber provided with a low-melting resin in a sheath component and a long fiber nonwoven fabric in which a low-melting resin fiber is mixed (see, for example, patent documents 1 to 2). Although these nonwovens have both pleating and pleat retention properties, the costs associated with their manufacture are high.

On the other hand, a filter reinforcing material using a polyethylene terephthalate long fiber nonwoven fabric has been proposed, which improves the pleated shape retaining performance and durability of the filter (see, for example, patent document 3). However, since a basis weight (basis weight) is added to the filter reinforcing material to improve rigidity and ensure shape retention performance, the filter unit has increased pressure loss and poor pleating performance due to an increase in thickness.

Reference list

Patent document

Patent document 1: japanese patent laid-open No.: 2008-231597

Patent document 2: japanese patent laid-open No.: 2000-199164

Patent document 3: japanese patent laid-open No.: 2011-000536

Summary of The Invention

Technical problem

The present invention has been made in view of the above circumstances, and a technical problem to be solved by the present invention is to obtain a long fiber nonwoven fabric having pleating properties suitable for a filter reinforcing material and having rigidity satisfying the pleat shape retaining properties.

Solution to the problem

As a result of intensive studies, the present inventors have found that the aforementioned problems can be solved by the following means, and have reached the present invention. Specifically, the present invention is as follows.

1. A long-fiber nonwoven fabric comprising fibers having a birefringence (Δ n) of 0.005 or more and 0.020 or less, a crystallinity of 25% or less and an average fiber diameter of 30 μm or more and 60 μm or less, the basis weight of the long-fiber nonwoven fabric being 50g/m or more²And is less than or equal to 120g/m²And a folding angle after pressing at 80 ℃ for 10 seconds under a pressure of 5.2kPa is 15 DEG or less.

2. The long-fiber nonwoven fabric according to the above 1, wherein an average value of aspect ratios of fiber cross sections of the fibers constituting the long-fiber nonwoven fabric is 1.05 or more and 1.2 or less.

3. The long-fiber nonwoven fabric according to the above 1 or 2, wherein the fibers constituting the long-fiber nonwoven fabric are single fibers made of a resin containing polyethylene terephthalate as a main component and 0.02 mass% or more and 5 mass% or less of a thermoplastic polystyrene-based copolymer mixed with the polyethylene terephthalate.

4. The long-fiber nonwoven fabric according to the above 4, wherein the glass transition point temperature of the thermoplastic polystyrene-based copolymer is 100 ℃ or more and 160 ℃ or less.

5. A filter reinforcing material using the long fiber nonwoven fabric according to any one of the above 1 to 4.

Advantageous effects of the invention

According to the present invention, with the above configuration, a long fiber nonwoven fabric suitable for a filter reinforcing material is obtained which is excellent in pleating performance, has rigidity with which close contact between pleats is unlikely to occur in a case of actual use, and is excellent in pleat shape retention performance. In addition, since the long fiber nonwoven fabric is made of fibers having a single component, it is possible to provide a long fiber nonwoven fabric that can be manufactured at low cost.

Description of the embodiments

The present inventors have conducted intensive studies to obtain a long fiber nonwoven fabric having excellent pleating properties, excellent pleat retention properties, and rigidity suitable for a filter reinforcing material. As a result, the present inventors have found that a long fiber nonwoven fabric suitable for a filter reinforcing material can be obtained by using a long fiber nonwoven fabric containing fibers mainly made of polyethylene terephthalate having a crystallinity of 25% or less.

Hereinafter, the long fiber nonwoven fabric of the present invention will be described in detail.

The birefringence (Δ n) of the fibers constituting the long fiber nonwoven fabric of the present invention is greater than or equal to 0.005 and less than or equal to 0.020, preferably greater than or equal to 0.007 and less than or equal to 0.015, and more preferably greater than or equal to 0.008 and less than or equal to 0.012. When the birefringence (Δ n) is less than 0.005, the long fiber nonwoven fabric has excellent pleating properties, but has reduced rigidity due to deformation of the fibers. Therefore, when a long fiber nonwoven fabric is actually used as a filter reinforcing material, contact or close contact between pleats may occur. When the birefringence (Δ n) is greater than 0.020, the long fiber nonwoven fabric has improved rigidity and can be used as a filter reinforcing material excellent in shape retention performance, but it is difficult to pleat the long fiber nonwoven fabric to have an arbitrary number of pleats with an arbitrary pitch between the pleats.

The crystallinity of the fibers constituting the long-fiber nonwoven fabric of the present invention is 25% or less, preferably 5% or more and 20% or less, and more preferably 10% or more and 15% or less. When the crystallinity is more than 25%, the long fiber nonwoven fabric has improved rigidity and can be used as a filter reinforcing material excellent in shape retention performance, but it is difficult to pleat the long fiber nonwoven fabric to have an arbitrary number of pleats with an arbitrary pitch between the pleats. Although the lower limit of the crystallinity is not particularly limited, when the crystallinity is less than 5%, the long fiber nonwoven fabric has reduced rigidity, and thus when the long fiber nonwoven fabric is actually used as a filter reinforcing material, contact or close contact between pleats may occur.

The average fiber diameter of the fibers constituting the long-fiber nonwoven fabric of the present invention is not less than 30 μm and not more than 60 μm, and the basis weight of the long-fiber nonwoven fabric is not less than 50g/m²And is less than or equal to 120g/m². Although the combination of the average fiber diameter of the fibers constituting the long-fiber nonwoven fabric and the basis weight of the long-fiber nonwoven fabric is not particularly limited, it is preferable to increase the average fiber diameter when the basis weight is reduced and to decrease the average fiber diameter when the basis weight is increased. Specifically, when the basis weight is 50g/m or more²And less than or equal to 70g/m²When the average fiber diameter is preferably 50 μm or more and 60 μm or less; when the basis weight is greater than or equal to 70g/m²And less than or equal to 90g/m²When the average fiber diameter is preferably 40 μm or more and 50 μm or less; and when the basis weight is greater than or equal to 90g/m²And is less than or equal to 120g/m²When used, the average fiber diameter is preferably greater than or equal to 30 μm and less than or equal to 40 μm.

The folding angle of the long fiber nonwoven fabric of the present invention after pressing at 80 ℃ for 10 seconds under a pressure of 5.2kPa is less than or equal to 15 °, preferably less than or equal to 10 °, and more preferably less than or equal to 5 °. When the folding angle is more than 15 °, the long fiber nonwoven fabric has improved rigidity and can be used as a filter reinforcing material excellent in shape retention performance, but it is difficult to pleat the long fiber nonwoven fabric to have an arbitrary number of pleats with an arbitrary pitch between the pleats. Although the lower limit of the folding angle after pressing at 80 ℃ under a pressure of 5.2kPa for 10 seconds is not particularly limited, it is usually 5 ° or more.

The average value of the aspect ratios of the fiber cross sections of the fibers constituting the fibrous nonwoven fabric of the present invention is preferably greater than or equal to 1.05 and less than or equal to 1.2. When the average value of the aspect ratio is less than 1.05, the long fiber nonwoven fabric has improved rigidity and can be used as a filter reinforcing material excellent in shape retention performance, but it is difficult to pleat the long fiber nonwoven fabric to have an arbitrary number of pleats with an arbitrary pitch between the pleats. When the average value of the aspect ratio is more than 1.2, the long fiber nonwoven fabric has excellent pleating properties, but has reduced rigidity due to deformation of the fibers. Therefore, when a long fiber nonwoven fabric is actually used as a filter reinforcing material, contact or close contact between pleats may occur.

The fibers constituting the long-fiber nonwoven fabric of the present invention are preferably single fibers made of a resin containing polyethylene terephthalate as a main component and a thermoplastic polystyrene-based copolymer mixed therewith. Polyethylene terephthalate is superior in mechanical strength, heat resistance, shape retention property, and the like, as compared with resins such as polyethylene and polypropylene. In order to effectively exhibit such an effect, when the blending amount of the thermoplastic polystyrene-based copolymer is considered, the content of the polyethylene terephthalate as a main component in the resin used for the fibers constituting the long-fiber nonwoven fabric of the present invention is preferably greater than or equal to 90 mass% and less than or equal to 99.8 mass%, more preferably greater than or equal to 93 mass% and less than or equal to 99.5 mass%, and further preferably greater than or equal to 94 mass% and less than or equal to 98 mass% with respect to 100 mass% of the entire long-fiber nonwoven fabric. It should be noted that other polyester resins, such as polypropylene terephthalate, polybutylene terephthalate, or polyethylene naphthalate, may be blended in addition to polyethylene terephthalate as long as the content thereof is 10 mass% or less.

It should be noted that in the present invention, "single fibers" means that they are not composite cross-sectional fibers such as core-sheath type composite cross-sectional fibers, side-by-side type composite cross-sectional fibers, and the like, and does not exclude mixing a resin composition as a resin for fibers. That is, in the present invention, fibers which are not in the form of composite cross-sectional fibers and use a mixed resin composition are included in the "single fiber" of the present invention.

The intrinsic viscosity of the polyethylene terephthalate used in the present invention is preferably greater than or equal to 0.3dl/g, more preferably greater than or equal to 0.4dl/g, further preferably greater than or equal to 0.5dl/g, and most preferably greater than or equal to 0.55 dl/g. By setting the intrinsic viscosity of the polyethylene terephthalate to 0.3dl/g or more, the resin is less likely to be thermally deteriorated, and the long fiber nonwoven fabric can have improved durability.

The glass transition point temperature of the thermoplastic polystyrene-based copolymer used in the present invention is preferably greater than or equal to 100 ℃ and less than or equal to 160 ℃, more preferably greater than or equal to 110 ℃ and less than or equal to 155 ℃, and further preferably greater than or equal to 120 ℃ and less than or equal to 150 ℃. In addition, the thermoplastic polystyrene-based copolymer is preferably incompatible in polyethylene terephthalate. When the glass transition point temperature of the thermoplastic polystyrene-based copolymer is higher than that of polyethylene terephthalate and is 100 ℃ or higher, crystallization of the fibers constituting the long-fiber nonwoven fabric can be suppressed. As an effect thereof, for example, by applying heat under planar constraint (planar constraint) described later, the fibers can be bonded to each other and can be further processed into a long fiber nonwoven fabric having a small dimensional change due to suppressed heat shrinkage. On the other hand, when the spinning productivity is considered, the glass transition point temperature is preferably less than or equal to 160 ℃. The glass transition point temperature is a value obtained by measurement at a temperature rising rate of 20 ℃ per minute in accordance with JIS K7122 (1987).

Although the thermoplastic polystyrene-based copolymer used in the present invention is not particularly limited as long as the glass transition point temperature thereof is greater than or equal to 100 ℃ and less than or equal to 160 ℃, it is preferably, for example, a styrene-conjugated diene block copolymer, an acrylonitrile-styrene copolymer, an acrylonitrile-butadiene-styrene copolymer, a styrene-acrylate copolymer or a styrene-methacrylate copolymer. Among these copolymers, a styrene-acrylate copolymer or a styrene-methacrylate copolymer is more preferable, and a styrene-methacrylate copolymer is further preferable. Examples of the styrene-methacrylate copolymer include styrene-methyl methacrylate-maleic anhydride copolymers. These copolymers may be contained alone or in combination. Examples of commercially available products include plexiglas hw55 produced by Rohm GmbH & co. kg, which is particularly preferred because it exhibits excellent effects with a small addition amount.

The blending amount of the thermoplastic polystyrene-based copolymer is preferably 0.02 mass% or more and 5 mass% or less, more preferably 0.05 mass% or more and 4 mass% or less, and further preferably 0.1 mass% or more and 3 mass% or less with respect to 100 mass% of the entire long fiber nonwoven fabric. The effect of the above mixture is obtained by setting the addition amount to 0.02 mass% or more. Although the upper limit of the blending amount of the thermoplastic polystyrene-based copolymer is not particularly limited, if it is blended excessively, the fibers are broken due to the difference in stretchability between the polyethylene terephthalate and the thermoplastic polystyrene-based copolymer, resulting in deterioration of workability. Therefore, the blending amount of the thermoplastic polystyrene-based copolymer is preferably 5% by mass or less.

The long fiber nonwoven fabric of the present invention is preferably a plane-restrained long fiber nonwoven fabric, particularly a plane-restrained spunbond nonwoven fabric. Planar restraint, as used herein, is the planar clamping of the web in the thickness direction and the planar application of pressure thereto. The plane constraint may be performed, for example, by: the entire web is pressed between a flat roll and a sheet-like body such as a felt belt, rubber belt or steel belt. In addition, although the web subjected to the temporary compression bonding is subjected to the permanent compression bonding (thermosetting) under the planar constraint in the present invention, this is different from the partial compression bonding in which the compression bonding is performed between the flat rolls and the engraving rolls or between the engraving rolls and the linear compression bonding in which the compression bonding is performed between the flat rolls. In the case of partial compression bonding, the fibers are partially fixed, so that stress concentrates on the compression bonded portions, and a long fiber nonwoven fabric which is difficult to pleat is obtained. Further, in the case of the linear compression bonding, the fibers are excessively completely compression bonded, so that the fibers are deformed, and a long fiber nonwoven fabric having low bending resistance and high pressure loss is obtained. On the other hand, when compression bonding is performed under planar restraint, thermal shrinkage of the web in the in-plane direction can be suppressed. As a result, in the obtained plane-restrained long fiber nonwoven fabric, the fibers are fixed to each other over the entire sheet while being suppressed from being deformed. Therefore, the plane-restrained long fiber nonwoven fabric has excellent bending resistance.

The long fiber nonwoven fabric of the present invention is preferably a long fiber nonwoven fabric that is not mechanically entangled. In the case of the long fiber nonwoven fabric subjected to mechanical interlacing, it is difficult to sharply pleat the long fiber nonwoven fabric, which is not preferable. Further, in the case of a nonwoven fabric made of short fibers, local deformation due to fiber slippage or the like occurs, and it is difficult to pleat the nonwoven fabric with equal pitches between pleats.

Next, a method for manufacturing the long fiber nonwoven fabric of the present invention will be described.

The method for producing the long fiber nonwoven fabric of the present invention comprises: a step of spinning at a ratio (hereinafter referred to as "draft ratio") between a take-up speed (take-up speed) and a discharge linear speed (discharge speed) of 200 or less, and a step of subjecting the web obtained after spinning to temporary compression bonding and then to permanent compression bonding under planar restraint.

First, predetermined amounts of polyethylene terephthalate and a thermoplastic polystyrene-based copolymer are blended and dried according to a conventional method, and then spun using a melt spinning machine.

In the present invention, it is preferable to set the draft ratio to 200 or less to obtain a long fiber nonwoven fabric having an appropriate birefringence (Δ n). When the draft ratio is more than 200, the crystallinity of the fibers constituting the long fiber nonwoven fabric becomes high, and a long fiber nonwoven fabric which is difficult to pleat is obtained. The draft ratio is more preferably less than or equal to 175, and further preferably less than or equal to 150.

The draw ratio is provided by the following equation:

(ratio between winding speed and unwinding Linear speed)

Draft ratio (ψ) is winding speed (Vs)/pay-off linear speed (V)₀)

(discharge line speed)

Pay-off line speed (V)₀) Single hole discharge (Q)/spinneret hole cross-sectional area (Da).

Although other spinning conditions are not particularly limited, it is preferable to spin from a spinneret at 0.3kg/cm or more²And less than or equal to 2.0kg/cm²The drying air is supplied to the ejector and the yarn is drawn. Further, by controlling the pressure of the supplied drying air within the above range, the take-up speed can be easily controlled within a desired range, and the yarn can be appropriately dried.

The yarn that is paid out is then cooled and the fibers of the yarn are opened and collected on a conveyor located below. Thus, a fiber web (long fiber fleece) can be obtained.

According to a usual method for producing a spunbond nonwoven fabric, the resulting web is subjected to embossing (embossing) or the like, which performs partial compression bonding between a flat nip roller and an engraved nip roller or between engraved nip rollers. However, since the web obtained by spinning at a low spinning speed as in the present invention has a low orientation and may shrink, when embossing or the like is performed on the web, problems such as width shrinkage and wrinkling occur. In the present invention, as described below, the temporary compression bonding is performed and then the permanent compression bonding is performed under planar restraint, which can easily suppress the occurrence of width shrinkage and wrinkles.

The temporary compression bonding is compression bonding of the web by applying pressure to the web in the thickness direction. The temporary compression bonding is performed to make planar restraint in the permanent compression bonding easy. For example, the thermal compression bonding may be performed using a pair of temporary thermal compression bonding rolls including two flat rolls at a surface temperature of each of the flat rolls of 60 ℃ or more and 140 ℃ or less and a pressing pressure of 5kN/m or more and 30kN/m or less. The surface temperature of each flat roll is more preferably 70 ℃ or more and 120 ℃ or less, and the pressing pressure is more preferably 7kN/m or more and 20kN/m or less.

Further, for easier permanent compression bonding, the fiber web subjected to temporary compression bonding may be subjected to water treatment, whereby water is sprayed on the fiber web by a sprayer so that the water content of the fiber web is 1 mass% or more and 30 mass% or less.

Then, permanent compression bonding is performed. Permanent compression bonding is the thermosetting and compression bonding of a web that has been temporarily compression bonded under planar restraint. As mentioned above, the planar confinement is preferably performed using flat rolls and sheets such as felt belts (felt belts), rubber belts or steel belts. Of these belts, a felt belt is particularly preferable because its surface is fibrous and it easily restrains the fiber web in the in-plane direction. Furthermore, when permanently compression-bonded under planar restraint, the fibers are fixed throughout the sheet. Thereby, deformation of the fiber is suppressed, and excellent bending resistance can be obtained.

The heat curing and the plane constraint are preferably performed under the conditions of a surface temperature of the roll of 120 ℃ or more and 180 ℃ or less, a pressing pressure (pressing pressure) of 10kPa or more and 400kPa or less, a processing time of 3 seconds or more and 30 seconds or less, and a processing speed of 1 m/min or more and 30 m/min or less.

The surface temperature of the roll is preferably set to 120 ℃ or more because the compression bonding is easily performed. The surface temperature of the roll is more preferably set to 130 ℃ or higher. On the other hand, the surface temperature of the roll is preferably set to 180 ℃ or less because excessive compression bonding is suppressed. The surface temperature of the roll is more preferably set to 160 ℃ or less.

The pressing pressure is preferably set to 10kPa or more because planar restraint is easily performed. The pressurization pressure is set more preferably to 30kPa or more, further preferably to 50kPa or more, particularly preferably to 100kPa or more, and most preferably to 200kPa or more. On the other hand, the pressing pressure is preferably set to be less than or equal to 400kPa because excessive compression bonding is suppressed. The pressurization pressure is more preferably set to 350kPa or less, and further preferably set to 300kPa or less.

The processing time is preferably set to 3 seconds or more because the compression bonding is easily performed. The processing time is more preferably set to 5 seconds or more. On the other hand, the working time is preferably set to 35 seconds or less because excessive compression bonding is suppressed. The processing time is more preferably set to 20 seconds or less, and further preferably set to 15 seconds or less.

By setting the machining speed to preferably 1 m/min or more, excessive compression bonding is suppressed. The processing speed is more preferably greater than or equal to 5 m/min. On the other hand, by setting the processing speed to preferably 30 m/min or less, the compression bonding is easily performed. The processing speed is more preferably less than or equal to 20 m/min.

Although the combination of the processing temperature (the surface temperature of the nip roller) and the processing time in the permanent compression bonding is not particularly limited, it is preferable to increase the processing time when the processing temperature is lowered and to decrease the processing time when the processing temperature is raised, so as to obtain a long-fiber nonwoven fabric comprising fibers having a suitable crystallinity.

Specifically, when the processing temperature is greater than or equal to 120 ℃ and less than 140 ℃, the processing time is preferably greater than or equal to 20 seconds and less than or equal to 35 seconds; when the processing temperature is greater than or equal to 140 ℃ and less than 160 ℃, the processing time is preferably greater than or equal to 10 seconds and less than or equal to 25 seconds; and when the processing temperature is greater than or equal to 160 ℃ and less than or equal to 190 ℃, the processing time is preferably greater than or equal to 3 seconds and less than or equal to 15 seconds.

The long fiber nonwoven fabric of the present invention obtained as described above is suitable for a filter reinforcing material, and is excellent in pleating performance and pleat shape retention performance.