Electrostatically charged nonwoven fabric

Abstract

To provide electrostatically charged nonwoven fabrics with a good balance of weather resistance, electrostatic resistance, and durability. [Solution] The electrostatically charged nonwoven fabric is composed of polyolefin resin fibers. The polyolefin resin contains a hindered amine light stabilizer and an antioxidant. The content of the hindered amine light stabilizer in the polyolefin resin is 105 ppm or more and 60,000 ppm or less. The content of the antioxidant in the polyolefin resin is 15 ppm or more and 30,000 ppm or less.

Description

Technical Field

[0004]

[0001] The present invention relates to a charged nonwoven fabric.

Background Art

[0002] Conventionally, a nonwoven fabric formed of a polyolefin resin and charged by utilizing frictional electrification or the like has been practically used as a filter (see, for example, Patent Document 1). In Patent Document 1, the nonwoven fabric is charged by utilizing static electricity generated when a fluid passes through the inside.

[0003] Further, Patent Document 1 discloses that the charged nonwoven fabric is formed of a polyolefin resin material containing at least one of a magnesium fatty acid salt, a magnesium alicyclic acid salt, and an aromatic magnesium salt, a hindered amine compound, and a polyolefin resin.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to increase the degree of charge of the charged nonwoven fabric and improve the filtering ability, there is room for improvement in the components constituting the charged nonwoven fabric and their proportions.

Means for Solving the Problems

[0006] The electrostatically charged nonwoven fabric for solving the above problems is an electrostatically charged nonwoven fabric composed of polyolefin resin fibers, wherein the polyolefin resin contains a hindered amine light stabilizer and an antioxidant, the content of the hindered amine light stabilizer in the polyolefin resin is 105 ppm or more and 60,000 ppm or less, and the content of the antioxidant in the polyolefin resin is 15 ppm or more and 30,000 ppm or less.

[0007] Hindered amine-based light stabilizers, a type of resin additive, have the function of suppressing degradation caused by light (ultraviolet light) (hereinafter referred to as degradation suppression function), as well as the function of increasing the degree of charge of resin materials (hereinafter referred to as charge promotion function).

[0008] According to the above configuration, by incorporating such hindered amine-based light stabilizers, it becomes possible to obtain the effect of improving weather resistance through degradation suppression and the effect of improving electrical resistance through charge acceleration. Moreover, according to the above configuration, such hindered amine-based light stabilizers and antioxidants having the function of preventing oxidation of resin materials (hereinafter referred to as oxidation prevention function) can be blended in a well-balanced ratio as described above. Therefore, in addition to improving weather resistance and electrical resistance by adding hindered amine-based light stabilizers, durability can also be improved by adding antioxidants. Thus, according to the above configuration, by blending two types of additives, light stabilizers and antioxidants, it is possible to impart weather resistance, electrical resistance, and durability to electrostatically charged nonwoven fabrics in a well-balanced manner. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a table showing the blending ratio of resin additives in an electrostatically charged nonwoven fabric according to one embodiment. [Figure 2] Figure 2 is a table showing the measurement results of collection efficiency and pressure loss for each embodiment. [Modes for carrying out the invention]

[0010] The following describes one embodiment of an electrostatically charged nonwoven fabric. The electrostatically charged nonwoven fabric of this embodiment is composed of polyolefin resin fibers. The polyolefin resin constituting the fibers contains a polyolefin resin, a hindered amine light stabilizer, and an antioxidant. The content of the hindered amine light stabilizer in the polyolefin resin is 105 ppm or more and 60,000 ppm or less. The content of the antioxidant in the polyolefin resin is 15 ppm or more and 30,000 ppm or less.

[0011] <Polyolefin resin> In the electrostatically charged nonwoven fabric of this embodiment, a polyolefin resin is used. Examples of polyolefin resins include polyethylene (PE) and polypropylene (PP). In this embodiment, polypropylene is used as the polyolefin resin.

[0012] The content of polyolefin resin in 100 parts by mass of the electrostatically charged nonwoven fabric is preferably 80 parts by mass or more, and most preferably 97 parts by mass or more. There is no particular upper limit to the content of polyolefin resin, but it is preferably 99 parts by mass or less.

[0013] <Hindered amine-based light stabilizers> Examples of hindered amine-based light stabilizers include the following (a) to (c).

[0014] (a) Reaction product of dimethyl butanediate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (Tinuvin® 622SF, manufactured by BASF Japan).

[0015] (i) Poly([6-{(1,1,3,3-tetramethylbutyl)amino}-1,3,5-triazine-2,4-diyl]{(2,2,6,6-tetramethyl-4-piperidyl)imino}-1,6-hexanediyl{(2,2,6,6-tetramethyl-4-piperidyl)imino}) (Kimasorb [registered trademark] 944FDL, manufactured by BASF Japan).

[0016] (c) Reaction product of 1,6-hexanediamine,N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl) polymer, 2,4,6-trichloro-1,3,5-triazine, N-butyl-1-butanamine, and N-butyl-2,2,6,6-tetramethyl-4-piperidineamine (Chimasorb 2020FDL, manufactured by BASF Japan).

[0017] As the hindered amine light stabilizer, one of the above (a) to (c) may be used alone, or two or more may be used in combination. However, the hindered amine light stabilizer is not limited to the above (a) to (c) and can be changed as desired.

[0018] Hindered amine-based light stabilizers, a type of resin additive, have the function of suppressing degradation caused by light (ultraviolet light) (hereinafter referred to as degradation suppression function), as well as the function of increasing the degree of charge of the resin material (hereinafter referred to as charge promotion function). Antioxidants, on the other hand, have the function of preventing oxidation of the resin material (hereinafter referred to as oxidation prevention function).

[0019] In this embodiment, based on the results of various experiments conducted by the inventor, the amount of the hindered amine light stabilizer is determined as follows, in such a manner that the degradation suppression function and charge promotion function of the hindered amine light stabilizer and the oxidation prevention function of the antioxidant are provided in a well-balanced manner. As shown in Figure 1, either the first embodiment, in which tinubine 622SF and kimasorb 944FDL are used in combination, or the second embodiment, in which tinubine 622SF and kimasorb 2020FDL are used in combination, is selected as the hindered amine light stabilizer.

[0020] When selecting the first aspect, the content ratio of Tinuvin 622SF in the polyolefin resin constituting the fiber is preferably 5 ppm or more and 10,000 ppm or less. In this embodiment, in this case, the content ratio of Tinuvin 622SF is set to 50 ppm. Also, when selecting the first aspect, the content ratio of Chimassorb 944FDL in the polyolefin resin constituting the fiber is 100 ppm or more and 50,000 ppm. In this embodiment, in this case, the content ratio of Chimassorb 944FDL is set to 26,000 ppm or less.

[0021] When selecting the second aspect, the content ratio of Tinuvin 622SF in the polyolefin resin constituting the fiber is 5 ppm or more and 10,000 ppm or less. In this embodiment, in this case, the content ratio of Tinuvin 622SF is set to 50 ppm. Also, when selecting the second aspect, the content ratio of Chimassorb 2020FDL in the polyolefin resin constituting the fiber is 100 ppm or more and 50,000 ppm. In this embodiment, in this case, the content ratio of Chimassorb 2020FDL is set to 26,000 ppm.

[0022] <Antioxidant> In this embodiment, the antioxidant includes a hindered phenol antioxidant and a phosphorus antioxidant.

[0023] For the charged non-woven fabric, specifically, the content ratio of the hindered phenol antioxidant in the polyolefin resin constituting the fiber is 10 ppm or more and 20,000 ppm or less. Also, the content ratio of the phosphorus antioxidant in the polyolefin resin is 5 ppm or more and 10,000 ppm or less.

[0024] <Hindered phenol antioxidant> Examples of the hindered phenol antioxidant include the following (e) and (o).

[0025] (E) Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox® 1010, manufactured by BASF Japan).

[0026] (O)Octadecyl-3-(3,5-di-tert.-butyl-4-hydroxyphenyl)-propionate (Irganox 1076, manufactured by BASF Japan). As a hindered phenol antioxidant, one of the above antioxidants may be used alone, or two or more may be used in combination. Furthermore, the hindered phenol antioxidant is not limited to (e) and (o) above and can be changed as desired.

[0027] The content of the hindered phenol antioxidant in the polyolefin resin constituting the fiber is preferably 10 ppm or more and 20,000 ppm or less. In this embodiment, the content of the hindered phenol antioxidant is set to 390 ppm.

[0028] Hindered phenol antioxidants, a type of resin additive, have both antioxidant and electrostatic charging functions. In this embodiment, based on the results of various experiments conducted by the inventors, the amount of hindered phenol antioxidant added is determined as follows, in such a manner that the antioxidant and electrostatic charging functions are appropriately imparted by the hindered phenol antioxidant. In this embodiment, Irganox 1010 and Irganox 1076 are used in combination as hindered phenol antioxidants. The content of Irganox 1010 in the polyolefin resin constituting the fibers is preferably 5 ppm or more and 10,000 ppm or less. In this embodiment, the content of Irganox 1010 is set to 20 ppm. Furthermore, the content of Irganox 1076 in the polyolefin resin constituting the fibers is preferably 5 ppm or more and 10,000 ppm or less. In this embodiment, the content of Irganox 1076 is set to 370 ppm.

[0029] <Phosphorus-based antioxidants> Examples of phosphorus-based antioxidants include (k) below. (C) Tris(2,4-di-tert-butylphenyl) phosphite (Irgaphos® 168, manufactured by BASF Japan).

[0030] Phosphorus-based antioxidants have an antioxidant function as well as a function to improve the thermal stability of resin materials (hereinafter referred to as thermal stabilization function). In this embodiment, based on the results of various experiments conducted by the inventors, the amount of phosphorus-based antioxidant to be blended is determined as follows, in such a manner that the antioxidant function and thermal stabilization function of the phosphorus-based antioxidant are appropriately imparted.

[0031] In this embodiment, Irgaphos 168 is used alone as the phosphorus-based antioxidant. The content of the phosphorus-based antioxidant (Irgaphos 168 in this embodiment) in the polyolefin resin constituting the fibers is preferably 5 ppm or more and 10,000 ppm or less. In this embodiment, the content of the phosphorus-based antioxidant is set to 20 ppm.

[0032] The electrostatically charged nonwoven fabric of this embodiment can be molded to an appropriate shape and thickness depending on the application. The average fiber diameter of the fibers constituting the electrostatically charged nonwoven fabric is preferably 0.001 to 100 μm, and more preferably 1.00 to 5.00 μm. If the average fiber diameter of the fibers is thicker than 100 μm, it is difficult to obtain a practical collection efficiency. If the average fiber diameter of the fibers is thinner than 0.001 μm, it is difficult to form an electrostatically charged nonwoven fabric.

[0033] Methods for forming the nonwoven fabric that will become the basis for the electrostatically charged nonwoven fabric include the spunbond method using continuous fibers, the meltblown method, and the flash spinning method. In this embodiment, the nonwoven fabric is formed using the meltblown method.

[0034] The method for charging a nonwoven fabric is not particularly limited as long as the desired properties can be obtained when the charged nonwoven fabric is used, but it is preferable to use a method in which liquid is brought into contact with or impacted by a liquid (liquid contact charging method). In this embodiment, a water flow charging method is employed in which water is brought into contact with or impacted by the fibers by methods such as suction, pressurization, or jetting. According to the water flow charging method, the nonwoven fabric is charged by utilizing the static electricity generated when water comes into contact with or impacts the fibers of the nonwoven fabric.

[0035] As shown in Figure 2, in this embodiment, four types of electrostatically charged nonwoven fabrics, specifically Examples 1-1, 1-2, 2-1, and 2-2, were formed. For each of the four types of electrostatically charged nonwoven fabrics, an experiment was conducted in which the electrostatically charged nonwoven fabric was placed in an air passage and air was flowed through the passage at a flow rate of 0.5 meters per second, and the collection efficiency and pressure loss of the electrostatically charged nonwoven fabric were measured. The measurement results of collection efficiency and pressure loss are described below.

[0036] <Example 1-1> In Example 1-1, the basis weight of the electrostatically charged nonwoven fabric was set to 12.6 grams per square meter (g / m2), and the average fiber diameter of the fibers constituting the electrostatically charged nonwoven fabric was set to 2.78 micrometers (μm). In Example 1-1, the collection efficiency of atmospheric dust by the electrostatically charged nonwoven fabric was 84.8 percent (%), and the pressure loss was 55 Pascals (Pa).

[0037] <Examples 1-2> In Example 1-2, the basis weight of the electrostatically charged nonwoven fabric was set to 12.6 g / m2, and the average fiber diameter of the fibers constituting the electrostatically charged nonwoven fabric was set to 3.24 μm. In Example 1-2, the collection efficiency of atmospheric dust by the electrostatically charged nonwoven fabric was 77.8%, and the pressure loss was 39 Pa.

[0038] In both Examples 1-1 and 1-2, the basis weight of the electrostatically charged nonwoven fabric was set to 12.6 g / m2. In both Example 1-1, where the average fiber diameter of the fibers was 2.78 μm, and Example 1-2, where it was 3.24 μm, a high collection efficiency of 77.8% or more and a low pressure loss of 55 Pa or less were obtained.

[0039] Furthermore, if the objective is to satisfy the requirement of a collection efficiency of 75% or higher for a charged nonwoven fabric with a basis weight of 12.6 g / m2, then Example 1-2, which is a charged nonwoven fabric with a larger average fiber diameter and lower pressure loss, can be adopted. This makes it possible to achieve low pressure loss in the charged nonwoven fabric when it is used as a filter. Specifically, by adopting Example 1-2, it is possible to reduce the pressure loss by 16 Pa compared to adopting Example 1-1 while maintaining a collection efficiency of 75% or higher. This reduction in pressure loss of the charged nonwoven fabric can be achieved by adjusting the composition of the resin additive to increase the charging efficiency and collection efficiency of the charged nonwoven fabric, as in this embodiment.

[0040] <Example 2-1> In Example 2-1, the basis weight of the electrostatically charged nonwoven fabric was set to 15.5 g / m2, and the average fiber diameter of the fibers constituting the electrostatically charged nonwoven fabric was set to 3.14 μm. In Example 2-1, the collection efficiency of atmospheric dust by the electrostatically charged nonwoven fabric was 86.6%, and the pressure loss was 51 Pa.

[0041] <Example 2-2> In Example 2-2, the basis weight of the electrostatically charged nonwoven fabric was set to 15.5 g / m2, and the average fiber diameter of the fibers constituting the electrostatically charged nonwoven fabric was set to 4.12 μm. In Example 2-2, the collection efficiency of atmospheric dust by the electrostatically charged nonwoven fabric was 62.7%, and the pressure loss was 32 Pa.

[0042] In both Examples 2-1 and 2-2, the basis weight of the electrostatically charged nonwoven fabric was set to 15.5 g / m2. In both Example 2-1, where the average fiber diameter of the fibers was 3.14 μm, and Example 2-2, where it was 4.12 μm, a high collection efficiency of 62.7% or more and a low pressure loss of 51 Pa or less were obtained.

[0043] Furthermore, if the objective is to satisfy the requirement of a collection efficiency of 60% or higher for a charged nonwoven fabric with a basis weight of 15.5 g / m2, then Example 2-2, which uses a charged nonwoven fabric with a larger average fiber diameter and lower pressure loss, can be adopted. This makes it possible to achieve low pressure loss in the charged nonwoven fabric when it is used as a filter. Specifically, by adopting Example 2-2, it is possible to maintain a collection efficiency of 60% or higher while reducing the pressure loss by 19 Pa compared to the case of adopting Example 2-1. This reduction in pressure loss in the charged nonwoven fabric can be achieved by adjusting the composition of resin additives to increase the charging efficiency and collection efficiency of the charged nonwoven fabric, as in this embodiment.

[0044] <Operation and Effects of This Embodiment> The operation and effects of this embodiment will now be described. (1) The electrostatically charged nonwoven fabric is composed of polyolefin resin fibers. The polyolefin resin contains a hindered amine light stabilizer and an antioxidant. The content of the hindered amine light stabilizer in the polyolefin resin is 105 ppm or more and 60,000 ppm or less. The content of the antioxidant in the polyolefin resin is 15 ppm or more and 30,000 ppm or less.

[0045] According to the above configuration, by incorporating a hindered amine-based light stabilizer having degradation suppression and charge-promoting functions, improvements in weather resistance due to the degradation suppression function and improvements in electrical resistance due to the charge-promoting function can be obtained. Moreover, according to the above configuration, such a hindered amine-based light stabilizer and an antioxidant having an oxidation-preventing function can be blended in a well-balanced ratio as described above. Therefore, in addition to improving weather resistance and electrical resistance by adding the hindered amine-based light stabilizer, durability can also be improved by adding the antioxidant. Thus, according to the above configuration, by blending two types of additives, a light stabilizer and an antioxidant, sufficient weather resistance, electrical resistance, and durability can be imparted to the electrostatically charged nonwoven fabric.

[0046] (2) The antioxidant includes a hindered phenol antioxidant. The content of the hindered phenol antioxidant in the polyolefin resin is 10 ppm or more and 20,000 ppm or less.

[0047] According to the above configuration, at least a portion of the antioxidant, which is one type of resin additive, can be composed of an appropriate amount of a hindered phenol-based antioxidant having a charge-promoting function. Therefore, while suppressing an increase in the content of the hindered amine-based light stabilizer, the charge performance of the charged nonwoven fabric can be improved by using the antioxidant, more specifically the hindered phenol-based antioxidant.

[0048] (3) The antioxidant includes a phosphorus-based antioxidant. The content of the phosphorus-based antioxidant in the polyolefin resin is 5 ppm or more and 10,000 ppm or less. According to the above configuration, a portion of the antioxidant having antioxidant function can be composed of an appropriate amount of phosphorus-based antioxidant having thermal stabilization function. Therefore, in addition to the effect of improving durability performance due to the antioxidant function, an effect of improving thermal stability due to the thermal stabilization function can be obtained. Moreover, according to the above configuration, by using a hindered phenol-based antioxidant and a phosphorus-based antioxidant in combination, it is possible to obtain an effect of reinforcing the antioxidant function compared to when only one of the hindered phenol-based antioxidant or the phosphorus-based antioxidant is used.

[0049] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0050] • In addition to polypropylene, polyethylene may be used as the polyolefin resin that constitutes the electrostatically charged nonwoven fabric. • As the hindered amine light stabilizer, either Kimasorb 2020FDL or Kimasorb 944FDL may be used alone. Alternatively, three types of hindered amine light stabilizers may be used in combination: Chinuvin 622SF, Kimasorb 2020FDL, and Kimasorb 944FDL. Furthermore, it is also possible to use only two types of hindered amine light stabilizers, such as Kimasorb 2020FDL and Kimasorb 944FDL. Other hindered amine light stabilizers besides Chinuvin 622SF, Kimasorb 2020FDL, and Kimasorb 944FDL can be used. Regardless of the configuration adopted, the content ratio of the hindered amine light stabilizer in the polyolefin resin should be set to, for example, 26050 ppm, or between 105 ppm and 60000 ppm.

[0051] • As the hindered phenol antioxidant, either Irganox 1010 or Irganox 1076 may be used alone. Alternatively, other hindered phenol antioxidants besides Irganox 1010 and Irganox 1076 may be used. Regardless of the configuration adopted, the content of the hindered phenol antioxidant in the polyolefin resin should be set to between 10 ppm and 20,000 ppm, for example, 390 ppm.

[0052] As for the phosphorus-based antioxidant, one other than Irgaphos 168 may be used alone, or Irgaphos 168 may be used in combination with one or more other phosphorus-based antioxidants, or multiple phosphorus-based antioxidants other than Irgaphos 168 may be used. In any of the configurations adopted, the content ratio of the phosphorus-based antioxidant in the polyolefin resin should be set to 5 ppm or more and 10,000 ppm or less, for example, 20 ppm.

[0053] • As an antioxidant, only one of hindered phenol-based antioxidants or phosphorus-based antioxidants may be used. In this configuration as well, the antioxidant content in the polyolefin resin should be set to 15 ppm or more and 30,000 ppm or less, for example, 410 ppm. [Explanation of Symbols]

[0054] Examples 1-1, 1-2, 2-1, 2-2…

Claims

1. A nonwoven fabric with electrostatic charge, composed of polyolefin resin fibers, The aforementioned polyolefin resin contains a hindered amine light stabilizer and an antioxidant. The content of the hindered amine light stabilizer in the polyolefin resin is 105 ppm or more and 60,000 ppm or less. The content ratio of the antioxidant in the polyolefin resin is 15 ppm or more and 30,000 ppm or less. Electrostatically charged nonwoven fabric.

2. The aforementioned antioxidant includes a hindered phenol antioxidant. The content of the hindered phenol antioxidant in the polyolefin resin is 10 ppm or more and 20,000 ppm or less. The electrostatically charged nonwoven fabric according to claim 1.

3. The aforementioned antioxidant includes a phosphorus-based antioxidant, The content of the phosphorus-based antioxidant in the polyolefin resin is 5 ppm or more and 10,000 ppm or less. The electrostatically charged nonwoven fabric according to claim 1 or 2.

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