JP2009221618A - Electret body of biodegradable nonwoven fabric, and filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electret body of nonwoven fabric which has biodegradability and a long charge life. <P>SOLUTION: A nonwoven fabric formed from an alloy fiber made of an aliphatic polyester-based resin and a polyolefin-based resin is electretized. The ratio (mass ratio) of the aliphatic polyester-based resin to the polyolefin-based resin is about 50/50-99/1 (especially 70/30-95/5). The aliphatic polyester-based resin may constitute a matrix phase in the alloy fiber and the polyolefin-based resin may constitute a disperse phase. The aliphatic polyester-based resin may be a polylactic acid-based resin and the polyolefin-based resin may be a polypropylene-based resin. The nonwoven fabric may be a melt-blown nonwoven fabric. The nonwoven fabric may contain a hindered amine-based compound. The nonwoven fabric is suitable for a filter such as a mask filter. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a biodegradable non-woven electret body and a filter.

  2. Description of the Related Art Conventionally, a fabric such as a nonwoven fabric or a textile product has a network structure, and thus has been used as a filter material such as an air filter or a mask filter. In recent years, in order to improve the filter characteristics of such a filter material, an electret treatment that imparts a relatively long-life static charge to a fabric such as a nonwoven fabric has been performed. The electret-treated non-woven fabric can capture fine particles by an electrostatic charge in addition to a filter mechanism having a network structure. In particular, electretized non-woven fabric can capture fine particles such as dust even if the fiber mesh is enlarged, so that both air permeability and filterability can be achieved. Known non-woven fabrics that are relatively easy to electret include, for example, fabrics made of polyolefin fibers such as polyethylene and polypropylene, and polyester fibers such as polyethylene terephthalate and polybutylene terephthalate.

  On the other hand, in recent years, use of biodegradable plastics is desired due to environmental problems. Under such circumstances, the use of biodegradable plastics is also being considered for electret fabric filters.

  For example, in Japanese Patent No. 3716969 (Patent Document 1), an electret body of a nonwoven fabric filter composed of polymer fibers mainly composed of an aliphatic polyester having an average fiber diameter of 0.1 to 20 μm and a melting point of 130 ° C. or higher. Is disclosed. This document describes that a nonwoven fabric is manufactured using a melt blown method, and a copolymer obtained by adding a higher aliphatic alcohol or a carboxylic acid to the terminal of polylactic acid is used as the aliphatic polyester. Japanese Patent Application Laid-Open No. 2004-10754 (Patent Document 2) proposes a non-woven electret body obtained by spinning a polylactic acid-based polymer prepared by adjusting the mixing ratio of D-form and L-form by a melt blown method. ing. However, these filters do not have sufficient charging effects, have large heat shrinkage of polylactic acid fibers, and have low processability.

  Japanese Patent Application Laid-Open No. 2005-511899 (Patent Document 3) proposes a fibrous electret filter manufactured by stretching an aliphatic polyester film such as polylactic acid to form a microfibril. This document discloses a method of forming microvoids by drawing and then microfibrillation, and exemplifies a semicrystalline polymer such as polypropylene as a void starting component. However, this filter also has insufficient charging effect and low productivity.

In addition, in the Japanese Patent Application Laid-Open No. 2007-197857 (Patent Document 4), the applicant of the present invention uses polylactic acid and polyolefin from the viewpoint of improving mechanical properties (such as heat shrinkage) of a nonwoven fabric composed of polylactic acid. A melt-blown nonwoven fabric composed of fibers composed of a polylactic acid composition containing polylactic acid / polyolefin = 50/50 to 99/1 is proposed. However, this document does not describe electretization.
Japanese Patent No. 3716969 (claims 1 and 2, paragraph [0008], example) JP 2004-10754 A (Claim 1, paragraphs [0037] to [0039], Examples) JP 2005-511899 A (paragraphs [0043] to [0050] [0078] [0106]) JP 2007-197857 A (Claims 1 and 5, paragraph [0028])

  Accordingly, an object of the present invention is to provide a nonwoven fabric electret body that is biodegradable and has a long charge life, and a filter composed of the electret body.

  Another object of the present invention is to provide a biodegradable nonwoven fabric electret body having a long charging life even under high temperature and high humidity, and a filter composed of the electret body.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have electretized a nonwoven fabric formed of an alloy fiber composed of an aliphatic polyester resin and an olefin resin without impairing high biodegradability. The inventors have found that the charging life can be improved and completed the present invention.

  That is, the nonwoven fabric of the present invention is formed of alloy fibers composed of an aliphatic polyester resin and an olefin resin, and is electretized. The ratio (mass ratio) between the aliphatic polyester resin and the olefin resin is about aliphatic polyester resin / olefin resin = 50/50 to 99/1 (especially 70/30 to 95/5). In the alloy fiber, the aliphatic polyester resin may constitute a matrix phase, and the olefin resin may constitute a dispersed phase. The aliphatic polyester resin may be a polylactic acid resin, and the olefin resin may be a polypropylene resin. The nonwoven fabric of the present invention may be a meltblown nonwoven fabric and may contain a hindered amine compound.

  The present invention also includes a filter (such as a mask filter) made of the nonwoven fabric.

  In the specification of the present application, the term “filter” is used to mean a member having a characteristic capable of capturing fine particles such as dust (mask, dust-proof garment, wiper, etc.) in addition to a filter having a filtration function.

  Since the nonwoven fabric electret body of the present invention is composed of alloy fibers of aliphatic polyester resin and olefin resin, it has biodegradability and a long charge life. In particular, it exhibits excellent electret properties even though it is a nonwoven fabric composed of rich fibers of an aliphatic polyester resin having high biodegradability and low electret effect. Furthermore, the charging life is long and the dimensional stability is excellent even under high temperature and high humidity.

[Nonwoven fabric]
The nonwoven fabric of the present invention is formed of alloy fibers composed of an aliphatic polyester resin and an olefin resin.

(Aliphatic polyester resin)
Aliphatic polyester resin is obtained by ring-opening polymerization of homopolyester or copolyester obtained by polycondensation of aliphatic dicarboxylic acid and aliphatic diol, homopolyester or copolyester of aliphatic oxycarboxylic acid, or cyclic ester. Homopolyester or copolyester that can be used. Further, the copolymer may be a copolymer of an aliphatic dicarboxylic acid, an aliphatic diol, an aliphatic oxycarboxylic acid and / or a cyclic ester, or a copolymer of an aliphatic oxycarboxylic acid and a cyclic ester. Good.

  Examples of the aliphatic dicarboxylic acid include aliphatic dicarboxylic acids having about 2 to 6 carbon atoms such as oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid. These aliphatic dicarboxylic acids can be used alone or in combination of two or more. Of these, aliphatic dicarboxylic acids having about 2 to 4 carbon atoms such as oxalic acid and succinic acid are preferred.

Examples of the aliphatic diol include C _2-10 alkanes such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, neopentyl glycol, hexanediol, octanediol, nonanediol, and decanediol. Diols are mentioned. These aliphatic diols can be used alone or in combination of two or more. Of these, C _2-6 alkanediols such as ethylene glycol and 1,4-butanediol are preferred.

Examples of the aliphatic oxycarboxylic acids include aliphatic C _2-6 oxycarboxylic acids such as glycolic acid, lactic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, and malic acid. These aliphatic oxycarboxylic acids can be used alone or in combination of two or more. Of these, aliphatic C _2-4 oxycarboxylic acids such as glycolic acid and lactic acid are preferred.

Examples of the cyclic ester include dimers of oxycarboxylic acids such as C _4-12 lactone such as propiolactone, butyrolactone, valerolactone, caprolactone, pivalolactone, undecalactone, 1,5-oxepane-2-one, glycolide, and lactide. Examples include the body. These cyclic esters can be used alone or in combination of two or more. Of these, C _4-10 lactones such as caprolactone and oxycarboxylic acid dimers such as lactide are preferable. In addition, as an initiator in ring-opening polymerization, for example, a bifunctional or trifunctional initiator, for example, an active hydrogen compound such as alcohol can be used.

Further, the copolymer may be a copolymer with other copolymer components other than the above components. Other copolymer components include poly C _2-6 alkylene glycol (poly C _2-4 alkylene glycol such as diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc.), aliphatic dicarboxylic acids having about 7 to 12 carbon atoms. Acids (pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, etc.), polyols (C _3-10 polyols such as glycerin, pentaerythritol, trimethylolpropane, sugars, etc.) may be included. Addition of alicyclic or aromatic diol (C _4-10 cycloalkanediol such as 1,4-cyclohexanedimethanol, bisphenol compound such as bisphenol A or ethylene oxide addition thereof, if necessary, within a range not impairing biodegradability Alicyclic or aromatic dicarboxylic acid [cycloaliphatic dicarboxylic acid or other alicyclic dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-sodium sulfoisophthalic acid, _C8-12 aromatic dicarboxylic acid such as 5-tetrabutylphosphonium isophthalic acid, etc.], alicyclic or aromatic oxycarboxylic acid (hydroxybenzoic acid, etc.) Aromatic hydroxycarboxylic acid Etc.) may be copolymerized.

Specifically, as the aliphatic polyester-based resin, for example, a polyester-based resin obtained by polycondensation of dicarboxylic acid and diol (for example, polyethylene oxalate, polypropylene oxalate, polybutylene oxalate, polyneo Pentylene oxalate, polyethylene malonate, polypropylene malonate, polyethylene succinate, polybutylene succinate, polyethylene adipate, polybutylene adipate and other poly C _2-6 alkylene C _2-6 carboxylates), polyoxycarboxylic acid Based polymers (for example, polyglycolic acid and polylactic acid), polylactone based polymers [for example, poly C _3-12 lactone based polymers such as polycaprolactone, etc.] and the like. Specific examples of the copolyester include, for example, a copolyester using two kinds of dicarboxylic acid components (for example, poly C _2-4 alkylene such as polyethylene succinate-adipate copolymer and polybutylene succinate-adipate copolymer). And succinate-adipate copolymer) and copolyesters obtained from a dicarboxylic acid component, a diol component, and a lactone (for example, polycaprolactone-polybutylene succinate copolymer). These aliphatic polyester resins can be used alone or in combination of two or more.

  Of these aliphatic polyester resins, polylactic acid resins are preferred because of their high biodegradability. Since lactic acid is obtained by fermenting starch such as corn and potato, which are non-petroleum raw materials, it is also excellent in terms of environmental conservation.

  The polylactic acid resin only needs to contain lactic acid as a main constituent unit. Lactic acid includes L-lactic acid, D-lactic acid, L-lactic acid and a mixture of D-lactic acid (DL-lactic acid or racemic body). These lactic acids can be used alone or in combination of two or more. Lactic acid is preferably a resin having high crystallinity from the viewpoint of improving the chargeability and dimensional stability, particularly the charge retention rate. As such a resin, the content of either lactic acid or L-lactic acid is 60% by mass or more (for example, 60 to 100% by mass), preferably 90% by mass or more (for example, 90 to 99.99. 99% by mass), more preferably 95% by mass or more (for example, 95 to 99.9% by mass) lactic acid (or lactide which is a dimer thereof) as a raw material, a polylactic acid resin (poly L-lactic acid) Based resin or poly D-lactic acid based resin).

  Furthermore, in order to obtain a polylactic acid resin having high crystallinity, it is preferable to synthesize a polylactic acid resin using lactic acid having a high L-form purity. That is, in the polylactic acid-based resin, for example, polylactic acid is mainly L-form, and the D-form ratio is 15% by mass or less (for example, 0 to 15% by mass, preferably 0. Polylactic acid adjusted to 01 to 10% by mass, preferably 0.1 to 5% by mass (particularly about 1 to 5% by mass) may be used.

  The amount of L-form or D-form in the polylactic acid-based resin can be measured, for example, using gas chromatography.

  In the polylactic acid-based resin, the ratio of lactic acid as a structural unit may be, for example, 50 mol% or more, preferably 80 to 100 mol% (for example, 80 to 99.9 mol) of all structural units. %), More preferably about 90 to 100 mol% (especially 95 to 100 mol%). Other structural units can be contained as needed within a range not impairing the object of the present invention.

  The copolymer is a copolymer of lactic acid (or lactide) and the other aliphatic oxycarboxylic acid, a copolymer of lactic acid (or lactide) and the other cyclic ester, lactic acid (or lactide) and the fat. And a copolymer of an aliphatic dicarboxylic acid and the aliphatic diol. Furthermore, you may copolymerize the other above-mentioned copolymerization component. Specifically, polylactic acid-glycolic acid copolymer, polylactic acid-hydroxypropionic acid copolymer, polylactic acid-hydroxybutyric acid copolymer, polylactic acid-polyethylene oxalate copolymer, polylactic acid-polypropylene ogiza Polylactic acid-polyethylene malonate copolymer, polylactic acid-polyethylene succinate, polylactic acid-polyethylene adipate, polylactide-glycolide copolymer, polylactide-propiolactone copolymer, polylactide-butyrolactone copolymer, polylactide- Examples include caprolactone copolymers.

  Aliphatic polyester resins (especially polylactic acid resins) may have free hydroxyl groups and / or carboxyl groups at their terminals, and these free functional groups are blocking agents (for example, carbodiimide compounds, etc.) It may be sealed with.

  The melt flow rate (MFR) of the aliphatic polyester resin (particularly polylactic acid resin) is a method according to JIS K 7210 (190 ° C., load 2.16 kgf), for example, 1 g / 10 min or more, preferably 3 It may be about ˜500 g / 10 minutes, more preferably about 5 to 100 g / 10 minutes (10 to 50 g / 10 minutes). When the MFR is in this range, the fluidity is improved, and by adjusting the MFR of the olefin resin described later, the phase separation structure of both resins can be adjusted, and the electret effect can be improved. Further, it is easy to obtain a non-woven fabric with improved spinnability, thin fiber diameter and uniform texture.

  The molecular weight of the aliphatic polyester-based resin (particularly polylactic acid-based resin) is not particularly limited. For example, the weight average molecular weight is 30,000 to 1,000,000, preferably 50,000 to 700,000, and more preferably. It is about 80,000 to 500,000 (particularly 100,000 to 300,000).

  The melting point of the aliphatic polyester-based resin (particularly polylactic acid-based resin) varies depending on the molecular weight, stereoregularity, the presence or absence of other copolymerized units, the copolymerization rate, etc., but is, for example, 95 to 230 ° C., preferably 110 to It is 200 degreeC, More preferably, it is about 125-175 degreeC (especially 150-175 degreeC). When the melting point is within this range, the spinnability, mechanical properties, heat resistance and the like of the alloy with the olefin resin are improved, and it is also preferable from the viewpoint of easy availability.

(Olefin resin)
Olefin resins include olefin homo- or copolymers. Examples of the olefin include α-C _2-10 olefins (preferably α-C) such as ethylene, propylene, 1-butene, isobutene, 4-methyl-1-butene, 1-pentene, and 3-methyl-1-pentene. _2-8 olefins, more preferably α-C _2-4 olefins). These olefins may be used alone or in combination of two or more. Of these olefins, ethylene and / or propylene are preferably contained.

  The olefin resin may be a copolymer of an olefin and a copolymerizable monomer. Examples of the copolymerizable monomer include polymerizable nitrile compounds (for example, (meth) acrylonitrile), (meth) acrylic monomers (for example, methyl (meth) acrylate, ethyl (meth) acrylate, etc. (Meth) acrylic acid esters, (meth) acrylic acid etc.), unsaturated dicarboxylic acids or derivatives thereof (maleic anhydride etc.), vinyl esters (eg vinyl acetate, vinyl propionate etc.), conjugated dienes ( Examples thereof include butadiene and isoprene. A copolymerizable monomer can be used individually or in combination of 2 or more types. The ratio of the copolymerizable monomer is 0 to 50 mol%, preferably 0.1 to 25 mol%, more preferably about 1 to 10 mol% in all monomers.

  Examples of the olefin resin include polyethylene resins [for example, low, medium or high density polyethylene, linear low density polyethylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-propylene-butene. -1 copolymer, ethylene- (4-methylpentene-1) copolymer, etc.], polypropylene resin (eg, polypropylene, propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene- And propylene-containing 80 mol% or more propylene-α-olefin copolymer such as butene-1 copolymer) and poly (4-methylpentene-1) resin. Examples of the copolymer include an ethylene- (meth) acrylate copolymer such as an ethylene-ethyl acrylate copolymer.

  The copolymer (a copolymer of olefins and a copolymer of olefins and copolymerizable monomers) includes a random copolymer, a block copolymer, or a graft copolymer.

  Furthermore, the olefin resin is a modified olefin resin modified with a compound having a functional group, particularly an acid-modified olefin resin modified with an unsaturated carboxylic acid or its anhydride (for example, ethylene- (meth) acrylic acid). A copolymer or its ionomer, maleic anhydride grafted polypropylene, etc.).

  These olefin resins can be used alone or in combination of two or more. Among these olefin resins, polypropylene resins are preferable because the electret effect and mechanical properties (such as dimensional stability) can be improved.

  The polypropylene resin may be a polypropylene copolymer (propylene homopolymer) or a polypropylene copolymer (propylene copolymer).

In the polypropylene resin, examples of the copolymerizable monomer in the copolymer include olefins other than propylene (for example, ethylene, 1-butene, 2-butene, 1-pentene, 1-hexene, 3-methylpentene, 4 -Α-C _2-6 olefins such as methylpentene), (meth) acrylic monomers [for example, (meth) acrylic acid C _1-6 such as methyl (meth) acrylate and ethyl (meth) acrylate Alkyl esters etc.], unsaturated carboxylic acids (eg maleic anhydride etc.), vinyl esters (eg vinyl acetate, vinyl propionate etc.), dienes (butadiene, isoprene etc.) and the like. These copolymerizable monomers can be used alone or in combination of two or more. Of these copolymerizable monomers, olefins, particularly ethylene is preferred. Copolymers include random copolymers, block copolymers, and graft copolymers.

  In the case of a copolymer, the proportion of the copolymerizable monomer may be 20 mol% or less, for example, about 0.1 to 10 mol%. Examples of the copolymer include propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, and maleic anhydride-modified polypropylene. In the present invention, among these polypropylene resins, polypropylene homopolymer is preferable from the viewpoint of fluidity and heat resistance.

  The MFR of the olefin resin (particularly polypropylene resin) is a method according to JIS K 7210 (230 ° C., load 2.16 kgf), for example, 10 g / 10 min or more, preferably 50 to 2000 g / 10 min, more preferably Is about 100 to 1500 g / 10 min (particularly 300 to 1200 g / 10 min).

  Furthermore, in the present invention, the ratio of MFR between the aliphatic polyester resin and the olefin resin varies depending on the mass ratio of both from the viewpoint of controlling the phase separation structure and improving the electret effect (particularly, aliphatic group). When the ratio of polyester resin is large), usually, aliphatic polyester resin / olefin resin = 1/1 to 1/200, preferably 1/3 to 1/150, more preferably 1/5 to 1/100. (Especially 1/10 to 1/80). If the MFR ratio is within this range, the olefin resin is sufficiently uniformly dispersed in the phase separation structure of the aliphatic polyester resin and the olefin resin, and the interface between the two resins is increased. The rate is increased, and the sustain rate of the electret effect (especially the sustain rate in a humid heat environment) is improved.

  The molecular weight of the olefin resin (particularly polypropylene resin) is not particularly limited. For example, the number average molecular weight is 3,000 to 500,000, preferably 5,000 to 300,000, and more preferably 10,000 to 100. , About 0000.

  The melting point of the olefin resin (particularly polypropylene resin) may be, for example, 140 to 180 ° C, preferably 145 to 175 ° C, and more preferably about 150 to 170 ° C.

  From the viewpoint of maintaining high biodegradability, the ratio of the aliphatic polyester resin and the olefin resin is preferably an aliphatic polyester resin. Specifically, the ratio (mass ratio) of both is aliphatic polyester resin / olefin resin = 50/50 to 99/1, preferably 60/40 to 97/3, more preferably 70/30 to 95. / 5 (especially 75/25 to 93/7). In the present invention, although the proportion of the aliphatic polyester resin having a low electret effect is large, it has a high electret effect by controlling the phase separation structure of both resins.

  The reason for this is that by melting and mixing the two resins having the above MFR values in the above ratio, the aliphatic polyester resin becomes a matrix phase and the olefin resin becomes a fine and uniform dispersed phase in the alloy fiber. This is presumably because charges can be stably held at the interface between the two resins.

(Structure of alloy fiber)
The structure of the alloy fiber is an alloy structure of an aliphatic polyester resin and an olefin resin. In particular, as described above, the aliphatic polyester resin constitutes a matrix phase, and the olefin resin constitutes a dispersed phase. A structure is preferred. In such a phase separation structure, the dispersed phase composed of the olefin resin is finely and uniformly dispersed in the matrix at the above-mentioned ratio, and the average diameter is, for example, 0.1 to 10 μm, preferably 0. It is about 2 to 5 μm, more preferably about 0.25 to 1 μm (particularly 0.3 to 0.5 μm).

  The cross-sectional shape of the alloy fiber (cross-sectional shape perpendicular to the length direction of the fiber) is a general solid cross-sectional shape such as a round cross-section or an irregular cross-section [flat shape, elliptical shape, polygonal shape, 3-14 leaf shape, It is not limited to T-shape, H-shape, V-shape, dogbone (I-shape), etc.], and may be a hollow cross-section, but is usually a round cross-section.

  The average fiber diameter of the alloy fiber can be selected from the range of, for example, about 0.1 to 100 μm from the viewpoint of flexibility and air permeability, for example, 0.2 to 20 μm, preferably 0.5 to 15 μm, and more preferably. Is about 0.7 to 12 μm. If the fiber diameter is too thin, it is difficult to produce the fiber itself, and it is difficult to ensure fiber strength. On the other hand, if the fiber diameter is too large, the fiber becomes stiff and it is difficult to express sufficient crimp. Furthermore, when it has such a thin fiber diameter, a filter characteristic will improve.

  The average fiber length of the alloy fibers is not particularly limited as long as the form of the nonwoven fabric can be maintained by the entanglement of the fibers, and can be selected according to the production method. For example, it can be 10 mm or more, preferably 20 mm or more. In the case of a meltblown nonwoven fabric, it is usually a continuous fiber.

(Optional component)
In addition to the resin, the alloy fiber preferably contains a compound (charging improver) that promotes or stabilizes charging in the fiber. As the chargeability improver, conventional additives can be used alone or in combination of two or more kinds. For example, triazine compounds [for example, 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-((hexyl) oxy) phenol and other triazine ring-containing phenols], aliphatic metal salts (for example, C _8-24 carboxylic acid metal salts such as magnesium stearate and aluminum stearate), etc. However, a hindered amine compound is preferable from the viewpoint that a high electret effect can be exhibited in combination with the resin. Examples of the hindered amine compound include a compound having at least one 2,2,6,6-tetramethylpiperidyl group in the molecule, and can be used from a low molecule to a polymer.

  Examples of the low-molecular hindered amine compound include 4-methoxy-2,2,6,6-tetramethylpiperidine, 2,2,6,6-tetramethyl-4-piperidylbenzoate, N- (2,2,6 , 6-Tetramethyl-4-piperidyl) dodecylsuccinimide, 1-[(3,5-di-t-butyl-4-hydroxyphenyl) propionyloxyethyl] -2,2,6,6-tetramethyl-4 -Piperidyl- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, bis- (2,2,6,6-tetramethyl-4-piperidyl) ogisalate, bis- (2,2,6,6) -Tetramethyl-4-piperidyl) adipate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl- -Piperidyl) sebacate, 1,2-bis (2,2,6,6-tetramethyl-4-piperidyloxy) ethane, bis- (2,2,6,6-tetramethyl-4-piperidyl) terephthalate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) -2-butyl-2- (3,5-di-t-butyl-4-hydroxybenzyl) malonate, N, N′-bis (2, 2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine, tetra (2,2,6,6-tetramethyl-4-piperidyl) butanetetracarboxylate, tetra (1,2,2,6,6) -Pentamethyl-4-piperidyl) butanetetracarboxylate, bis (2,2,6,6-tetramethyl-4-piperidyl) di (tridecyl) butanetetracarboxylate, bi (1,2,2,6,6-pentamethyl-4-piperidyl) di (tridecyl) butanetetracarboxylate, 3,9-bis [1,1-dimethyl-2- {tris (2,2,6, 6-tetramethyl-4-piperidyloxycarbonyloxy) butylcarbonyloxy} ethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-bis [1,1-dimethyl-2 -{Tris (1,2,2,6,6-pentamethyl-4-piperidyloxycarbonyloxy) butylcarbonyloxy} ethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, 5,8,12-tetrakis [4,6-bis {N- (2,2,6,6-tetramethyl-4-piperidyl) butylamino} -1,3,5-triazin-2-yl] -1 5,8,12-tetraazadodecane and the like.

  Examples of the polymer hindered amine compound include 1- (2-hydroxyethyl) -2,2,6,6-tetramethyl-4-piperidinol / dimethyl succinate condensate, 2-t-octylamino-4,6. -Dichloro-s-triazine / N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine condensate, N, N'-bis (2,2,6,6- And tetramethyl-4-piperidyl) hexamethylenediamine / dibromoethane condensate.

  These hindered amine compounds can be used alone or in combination of two or more. Of these hindered amine compounds, high molecular hindered amine compounds are preferred because of their high charging effect sustainability. As the polymer hindered amine compounds, “Kimasoap 944” and “Tinuvin 622” manufactured by Ciba Japan Co., Ltd. are easily available as commercial products.

  The proportion of the charge improver is, for example, 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, and more preferably 0 to 100 parts by mass in total of the aliphatic polyester resin and the olefin resin. It is about 5-4 mass parts (especially 1-3 mass parts).

  Alloy fibers are further added to conventional additives such as stabilizers (heat stabilizers such as copper compounds, UV absorbers, light stabilizers other than hindered amine compounds, antioxidants, etc.), antibacterial agents, deodorants, and perfumes , Colorants (dyeing pigments, etc.), fillers, flame retardants, plasticizers, lubricants, crystallization rate retarders and the like may be contained. These additives can be used alone or in combination of two or more. These additives can be selected depending on the type, for example, 0.01 to 30 parts by mass, preferably 0.1 to 20 parts by mass with respect to 100 parts by mass in total of the aliphatic polyester resin and the olefin resin. Part, more preferably 0.3 to 10 parts by mass (particularly 0.5 to 5 parts by mass).

  Furthermore, the alloy fiber is a ratio that does not impair the properties of the resin, and other resins such as acrylic resins, polyvinyl acetal resins, polyvinyl chloride resins, polyvinylidene chloride resins, styrene resins, aromatic polyesters. Resin, polyamide resin, polycarbonate resin, polyparaphenylene benzobisoxazole resin, polyphenylene sulfide resin, polyurethane resin, cellulose resin and the like may be included. The ratio of other resin can be mix | blended in the range which does not impair biodegradability and an electret effect, for example, is 10 mass parts or less (for example, 0-0 mass) with respect to a total of 100 mass parts of aliphatic polyester-type resin and olefin resin. 10 parts by mass), preferably 5 parts by mass or less (for example, 0.01 to 5 parts by mass), and more preferably 3 parts by mass or less (for example, 0.1 to 3 parts by mass).

  In addition, components other than a resin component among the said arbitrary components may be mixed with the said resin, may be contained in the alloy fiber, and may be adhere | attached (supported) on the surface of a fiber (nonwoven fabric). When it is contained in the fiber, it is mixed with the spinning dope, and when it is supported on the fiber surface, it is added to the nonwoven fabric. On the other hand, the resin component is usually contained in the fiber.

(Other fibers)
Although the nonwoven fabric of this invention is comprised with the said alloy fiber, in the range which does not impair biodegradability and an electret effect, in addition to the said alloy fiber, it may be mixed with another fiber. Other fibers include conventional fibers such as organic fibers (polyvinyl alcohol fibers, acrylonitrile fibers, polyacetal fibers, aromatic polyester fibers, polyamide fibers, polyurethane fibers, cellulose fibers, etc.), inorganic fibers (Glass fiber, carbon fiber, etc.). These other fibers can be used alone or in combination of two or more.

  The ratio (mass ratio) between the alloy fiber and the other fiber is, for example, alloy fiber / other fiber = 80/20 to 100/0 (for example, 80/20 to 99.5 / 0.5), preferably 90. / 10 to 100/0 (for example, 90/10 to 99/1), more preferably about 95/5 to 100/0.

(Nonwoven fabric structure and electret body)
The nonwoven fabric of the present invention has a structure in which each fiber is entangled with each other and restrained or hooked, and its external shape may be selected depending on the application, but is usually plate-shaped or sheet-shaped.

The basis weight of the nonwoven fabric can be selected from a range of about 0.1 to 500 g / m ² , for example, 0.5 to 200 g / m ² , preferably 1 to 80 g / m ² , and more preferably 3 to 50 g / m. It is about ² . The thickness of a nonwoven fabric can be selected from the range of about 0.1-10 mm, for example, is 0.2-5 mm, for example, Preferably it is 0.3-3 mm, More preferably, it is about 0.4-2 mm. When the basis weight and thickness are in this range, the balance between the breathability, flexibility and strength of the nonwoven fabric is improved.

The air permeability of the nonwoven fabric is 0.1 cm ³ / (cm ² · sec) or more as measured by the Frazier method, for example, 1 to 500 cm ³ / (cm ² · sec), preferably 5 to 300 cm ³ / ( cm ² · sec), more preferably about 10 to ²⁰⁰ cm ³ / (cm ² · sec).

  The nonwoven fabric of the present invention is formed of the alloy fiber and is electretized.

[Method for producing nonwoven fabric]
The manufacturing method of the nonwoven fabric of this invention includes the web-forming process which webs an alloy fiber, and the electret process which gives an electric charge to the obtained fiber web (nonwoven fabric) and charges it.

  In the web forming process, a conventional method can be used. For example, a dry method (carding method or air lay method) using a staple fiber or a wet method may be used. The direct method in which chemical conversion is directly connected is preferred. Among them, the melt blown method is particularly preferable because a binder is not required and a nonwoven fabric having a small fiber diameter and excellent filter characteristics can be easily produced.

  In the melt blown method, a fiber web is obtained by blowing and collecting the obtained fibers with a high-temperature gas while melt spinning a mixture of aliphatic polyester resin and olefin resin. Conventional conditions can be used as manufacturing conditions in the melt blown method.

  Specifically, aliphatic polyester resins and olefin resins (hindered amine compounds and other additives as necessary) are melt-kneaded using a conventional mixer (for example, a melt-kneading extruder). The The melting temperature is not particularly limited as long as the aliphatic polyester resin and the olefin resin can be melted. For example, the temperature is 140 to 260 ° C, preferably 160 to 240 ° C, and more preferably about 180 to 220 ° C.

  The aliphatic polyester resin (particularly polylactic acid resin) is preferably dried in advance on the raw material pellets before being subjected to melt spinning. The temperature of the drying treatment is, for example, 50 to 120 ° C., preferably 60 to 100 ° C., more preferably about 70 to 90 ° C., and the drying time is, for example, 30 minutes or more (for example, 30 minutes to 24 hours). , Preferably 1 to 12 hours, more preferably about 2 to 6 hours.

  The resin composition melt-kneaded by the mixer is supplied to the spinneret. Spinning holes are usually formed in a row at the spinneret, and the interval between the spinning holes is, for example, 100 to 5000 holes / m, preferably 500 to 3000 holes / m, and more preferably 1000 to 2000 holes / m. m. The spinning temperature is, for example, about 150 to 300 ° C, preferably about 180 to 280 ° C, and more preferably about 200 to 260 ° C. The amount of fibers discharged from the spinneret is, for example, about 100 to 500 g / m, preferably about 200 to 400 g / m, and more preferably about 250 to 300 g / m.

  In order to blow off the spun fiber onto a support such as a net, a method of blowing high temperature air from a slit formed in the vicinity of the spinneret is usually used. The temperature of air is usually the same temperature as the spinning temperature. The pressure of the blowing air is, for example, about 0.1 to 2 MPa, preferably about 0.2 to 1 MPa, and more preferably about 0.3 to 0.5 MPa.

  In the electretization step, an electric charge can be imparted to the obtained fiber web (nonwoven fabric) by a conventional electretization treatment. Conventional methods include, for example, a method of applying an electric charge by friction or contact, a method of irradiating active energy rays (for example, electron beam, ultraviolet ray, X-ray, etc.), a method of utilizing gas discharge such as corona discharge or plasma. And a method of applying a high electric field and a method of applying ultrasonic vibration via a polar liquid such as water. Of these methods, the corona discharge treatment method using a needle electrode or the like is preferable from the viewpoint that a high charge can be easily applied. In the corona discharge, the treatment temperature is, for example, from room temperature to about 100 ° C. (particularly 50 to 90 ° C.), and the treatment time is, for example, about 1 second to 1 minute (particularly 5 to 30 seconds).

  The nonwoven fabric thus obtained is usually plate-shaped or sheet-shaped, and may be used as it is, but may be processed into a desired shape by cutting or the like depending on the application. . The obtained plate-like or sheet-like molded product is obtained by conventional thermoforming, for example, compression molding, pressure forming (extrusion pressure forming, hot plate pressure forming, vacuum pressure forming, etc.), free blow molding, vacuum forming, bending. Processing, matched mold molding, hot plate molding, wet heat press molding, etc. may be used, but since the decrease in electret effect due to thermoforming can be suppressed, the fixed meltblown nonwoven fabric is cut without using a binder component. It is preferable to process.

  Since the nonwoven fabric of the present invention has charging properties, it can be used for condenser microphones, ultrasonic diagnostic transducers, etc., but since it is an electret body having air permeability, in particular, applications that require a filter function, In particular, it is suitable for applications that collect fine particles such as dust. Examples of such applications include air clothes, masks or mask filters, medical clothes such as wipers and medical caps, and dustproof clothes for clean rooms.

  In particular, it is particularly suitable as a mask or a mask filter because it can maintain the dust collecting function of fine particles even under high humidity. The mask is composed of a main body including a mask filter and an ear hook member, and may be a planar mask or a three-dimensional mask in which a region corresponding to the nose is bulged in a convex shape. Good. In these masks, the entire mask may be composed of the nonwoven fabric of the present invention, or only the mask filter may be composed of the nonwoven fabric of the present invention.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In addition, each physical-property value in an Example was measured with the following method. In the examples, “%” is based on mass unless otherwise specified.

(1) Melt flow rate (MFR)
Using a melt indexer (Takara Kogyo Co., Ltd., “L244”), in accordance with JIS K 7210, polylactic acid is subjected to a temperature of 190 ° C. and a load of 2.16 kgf, and polypropylene is a temperature. MFR was measured under the conditions of 230 ° C. and a load of 2.16 kgf.

(2) Average fiber diameter (μm)
The nonwoven fabric was photographed with an electron microscope (magnification 1000 times), the diameter of 50 arbitrary unfused fibers in the photograph was measured, and the average value was calculated.

(3) Weight per unit (g / m ² )
The non-woven fabric was cut to prepare a test piece having a length of 20 cm × 20 cm in width, and measured at three locations along the width direction of the test piece in accordance with JIS L1096, and the average value was calculated.

(4) Collection efficiency, pressure loss, and QF value The filter characteristics of the composite fiber sheet were evaluated using a filter evaluation device (manufactured by Shibata Kagaku Co., Ltd., AP-6310FP). First, the test sample was attached to the measurement cell so that the diameter of the filtration surface was 85 mm. In this state, silica dust having a maximum diameter of 2 μm or less and a number average diameter of 0.5 μm was used as test dust, and dust-containing air adjusted to a dust concentration of 30 ± 5 mg / m ³ was filtered with a filter. Flow for 1 minute at a flow rate of 30 liters / minute through the set measurement cell, and measure the dust concentration D1 on the upstream side and the dust concentration D2 on the downstream side (after filtration) using a light scattering mass densitometer. The collection efficiency was sought.

Collection efficiency (%) = {(D1-D2) / D1} × 100
Further, a differential pressure gauge was disposed between the upstream side and the downstream side of the measurement cell in the filter evaluation apparatus, and the differential pressure (pressure loss) at a flow rate of 30 liters / minute was measured. Furthermore, the QF value was determined by the following equation from the values of the natural logarithm of the filter transmittance produced from the collection efficiency and the pressure loss.

QF (1 / Pa) = − ln (100−ΔE) / ΔP
[Wherein ΔE represents collection efficiency (%) and ΔP represents pressure loss (Pa)].

(5) Thermally stimulated current Thermally stimulated current is evaluated by a thermally stimulated current (TSDC) curve. TSDC curve refers to the movement and orientation of charges associated with molecular motion when an electrode is attached to one side of an electret film, connected to a high-sensitivity ammeter, and heated at a constant heating rate while the electret body is sandwiched between electrodes. It means a curve graph showing a change in current caused by a change in polarization state, and current peaks appear in various temperature ranges.

(6) Charging effect maintenance rate under wet heat Using a constant temperature and humidity machine (Isuzu Seisakusho Co., Ltd., μ series), the sample was allowed to stand for 24 hours under the conditions of a temperature of 80 ° C. and a relative humidity of 60%. The collection efficiency of this sample was measured by the above method, and the retention rate was calculated from the difference from the initial performance as shown in the following formula.

    Charging effect maintenance rate (%) = (collection efficiency after wet heat treatment) / (initial collection efficiency) × 100.

(7) Dry Heat Shrinkage of Nonwoven Fabric A test piece having a width of 5 cm and a length of 30 cm was cut out from the nonwoven fabric, and the test piece was placed in a constant temperature oven at a temperature of 100 ° C. and left for 1 minute to be heated. After heating, it was taken out from the oven, cooled to room temperature, and the dry heat shrinkage in the length direction was determined based on the following formula.

Dry heat shrinkage (%) = {(A0−A1) / A0} × 100
(In the formula, A0 represents the length of the test piece before heating, and A1 represents the length of the test piece after heating).

Example 1
Polylactic acid [manufactured by Nature Works, trade name “6201D”, MFR (190 ° C., 2.16 kgf) = 15 g / 10 min, copolymerization ratio of D-lactic acid = 1.5 mol%] is dried at 80 ° C. for 4 hours. Pellets and polypropylene pellets (manufactured by Prime Polymer Co., Ltd., MFR (230 ° C., 2.16 kgf) = 900 g / 10 min) were mixed at a mass ratio of polylactic acid pellets / polypropylene pellets = 90/10, A total of 99.5 parts by mass of the mixed pellets and 0.58 parts by mass of a hindered amine compound (“Kimasoap 944” manufactured by Ciba Japan Co., Ltd.) were supplied to an extruder of a melt blown nonwoven fabric production apparatus. After melting at 200 ° C. with this extruder, a nozzle having a spinning hole number of 1300 holes / m is discharged at a spinning temperature of 240 ° C. and a discharge amount of 270 g / m, and at the same time from a slit provided in the vicinity of the spinning hole, a temperature of 250 ° C., pressure A fiber blown with a hot air of 0.25 MPa was refined and collected on a net conveyor located 15 cm below the die to produce a melt blown nonwoven fabric having a basis weight of 30 g / m ² . Further, this nonwoven fabric was subjected to electret treatment for 10 seconds under the conditions of an electrode distance of 25 mm, an applied voltage of −25 kV, and a temperature of 80 ° C. using a corona method electret device having needle-like electrodes. Table 1 shows the results of measuring the collection efficiency, pressure loss, QF value, charging effect maintenance rate, and dry heat shrinkage rate of the electret body obtained. Furthermore, the measurement result of a thermally stimulated current is shown in FIG.

Example 2
Polylactic acid [manufactured by Nature Works, trade name “6201D”, MFR (190 ° C., 2.16 kgf) = 15 g / 10 min, copolymerization ratio of D-lactic acid = 1.5 mol%] is dried at 80 ° C. for 4 hours. Example 1 except that the pellets of polypropylene and polypropylene [manufactured by Prime Polymer Co., Ltd., MFR (230 ° C., 2.16 kgf) = 900 g / 10 min] are mixed at a mass ratio of polylactic acid / polypropylene = 80/20. In the same manner, an electret body was obtained. The results are shown in Table 1 and FIG.

Example 3
Polylactic acid [manufactured by Nature Works, trade name “6201D”, MFR (190 ° C., 2.16 kgf) = 15 g / 10 min, copolymerization ratio of D-lactic acid = 1.5 mol%] is dried at 80 ° C. for 4 hours. Example 1 except that the pellets of polypropylene and polypropylene [manufactured by Prime Polymer Co., Ltd., MFR (230 ° C., 2.16 kgf) = 600 g / 10 min] are mixed at a mass ratio of polylactic acid / polypropylene = 80/20. In the same manner, an electret body was obtained. The results are shown in Table 1 and FIG.

Comparative Example 1
Other than using pellets of polylactic acid [manufactured by Nature Works, trade name “6201D”, MFR (190 ° C., 2.16 kgf) = 15 g / 10 min, D-lactic acid copolymerization ratio = 1.5 mol%] alone Obtained an electret body in the same manner as in Example 1. The results are shown in Table 1 and FIG.

Comparative Example 2
An electret body was obtained in the same manner as in Example 1 except that a pellet of polypropylene [manufactured by Prime Polymer Co., Ltd., MFR (230 ° C., 2.16 kgf) = 900 g / 10 min] was used alone. The results are shown in Table 1 and FIG.

  As is clear from the results in Table 1, the electret bodies of the examples have high collection efficiency and QF value, and low pressure loss loss and dry heat shrinkage. On the other hand, in the electret body of Comparative Example 1, the charging effect maintenance rate under wet heat decreased, and contraction occurred due to the influence of wet heat.

FIG. 1 is a graph showing measurement results of thermally stimulated currents of nonwoven fabric electret bodies in Examples and Comparative Examples.

Claims (8)

  A non-woven fabric formed of alloy fibers made of an aliphatic polyester resin and an olefin resin and electretized.   The nonwoven fabric according to claim 1, wherein the ratio (mass ratio) between the aliphatic polyester resin and the olefin resin is aliphatic polyester resin / olefin resin = 50/50 to 99/1.   The ratio (mass ratio) between the aliphatic polyester resin and the olefin resin is aliphatic polyester resin / olefin resin = 70/30 to 95/5, and the aliphatic polyester resin is an alloy fiber. The nonwoven fabric of Claim 1 or 2 which comprises a matrix phase and an olefin resin comprises a dispersed phase.   The nonwoven fabric according to any one of claims 1 to 3, wherein the aliphatic polyester resin is a polylactic acid resin and the olefin resin is a polypropylene resin.   It is a melt blown nonwoven fabric, The nonwoven fabric in any one of Claims 1-4.   The nonwoven fabric in any one of Claims 1-5 containing a hindered amine type compound.   The filter comprised with the nonwoven fabric in any one of Claims 1-6.   The mask filter comprised with the nonwoven fabric in any one of Claims 1-6.

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