Nonwoven fabric and method for producing same

Abstract

Provided is a nonwoven fabric including fibers formed from a resin composition containing: a polyester resin (A); and a polylactic acid polymer (B). The polyester resin (A) includes: a unit derived from a polyhydric alcohol (a1); and a unit derived from a polyvalent carboxylic acid (a2). The polyhydric alcohol (a1) includes a C4 or higher aliphatic diol (a1-1) having an alkyl group as a branched chain.

Description

Nonwoven fabric and its manufacturing method

[0001] The present invention relates to a nonwoven fabric and a method for producing the same.

[0002] From the perspective of environmental protection, active research is being conducted into bioplastics. Bioplastics such as polylactic acid polymers are made from renewable plant-derived resources such as corn, which are produced through photosynthesis, and are expected to be used in a wide range of fields.

[0003] However, it is known that nonwoven fabrics made of polylactic acid polymers undergo thermal shrinkage when heated. Therefore, a technique has been proposed in which polypropylene is blended as a modifier for polylactic acid polymers to produce polylactic acid compositions (see, for example, Patent Document 1). This technique can reduce the degree of thermal shrinkage that occurs in the resulting nonwoven fabric when heated. Low thermal shrinkage is expected to facilitate smooth and easy processing, treatment, and compounding.

[0004] Patent No. 4757040

[0005] However, in nonwoven fabrics, further improvements are required in addition to the property of low heat shrinkage.

[0006] The present inventors have investigated nonwoven fabrics obtained by the technology described in Patent Document 1 and found that, for example, no improvement in elongation is observed. Furthermore, it has been found that if the melt mass flow rate (MFR) is not adjusted in a resin composition containing polypropylene and a polylactic acid polymer as described in Patent Document 1, spinning stability during formation of the nonwoven fabric is poor, resulting in defects (e.g., shot (polymer lumps), fly ash) in some regions of the obtained nonwoven fabric and poor yield.

[0007] Therefore, a first object of the present invention is to provide a nonwoven fabric having excellent low heat shrinkage properties and excellent elongation properties, and a method for producing the same.

[0008] A second object of the present invention is to provide a nonwoven fabric with excellent productivity and a method for producing the same.

[0009] Other objects of the present invention can be understood by those skilled in the art from the disclosure of this specification.

[0010] As a result of intensive research to solve the above problems, the present inventors have conceived the following invention and found that the above problems can be solved.

[0011] [1] A nonwoven fabric comprising fibers formed from a resin composition containing a polyester resin (A) and a polylactic acid polymer (B), wherein the polyester resin (A) contains units derived from a polyhydric alcohol (a1) and units derived from a polycarboxylic acid (a2), and the polyhydric alcohol (a1) contains an aliphatic diol (a1-1) having 4 or more carbon atoms and having an alkyl group as a branched chain. [2] The nonwoven fabric according to [1], wherein the polycarboxylic acid (a2) is an aliphatic dicarboxylic acid (a2-1). [3] The nonwoven fabric according to [2], wherein the aliphatic dicarboxylic acid (a2-1) is at least one selected from adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. [4] The nonwoven fabric according to any one of [1] to [3], wherein the polyester resin (A) has a number-average molecular weight of 500 to 100,000. [5] The nonwoven fabric according to any one of [1] to [4], which contains 0.1 to 50 parts by mass of the polyester resin (A) per 100 parts by mass of the polylactic acid polymer (B). [6] The nonwoven fabric according to any one of [1] to [5], wherein the polycarboxylic acid (a2) is an aliphatic dicarboxylic acid (a2-1), the aliphatic dicarboxylic acid (a2-1) includes adipic acid, and the number average molecular weight of the polyester resin (A) is 500 to 100,000. [7] The nonwoven fabric according to any one of [1] to [5], wherein the polycarboxylic acid (a2) is an aliphatic dicarboxylic acid (a2-1), the aliphatic dicarboxylic acid (a2-1) includes sebacic acid, and the number average molecular weight of the polyester resin (A) is 500 to 100,000. [8] The nonwoven fabric according to any one of [1] to [7], which contains 0.001 to 3.0 parts by mass of a cyclic ester compound (C) per 100 parts by mass of the polylactic acid polymer (B). [9] The nonwoven fabric according to any one of [1] to [8], wherein the polyester resin (A) is a polyester diol.

[10] The nonwoven fabric according to any one of [1] to [9], wherein the resin composition has a melt mass flow rate (MFR) of 40 g / 10 min or more and 300 g / 10 min or less, measured under conditions of a temperature of 190°C and a load of 2.16 kg.

[11] A method for producing a nonwoven fabric according to any one of [1] to

[10] , comprising the steps of melt-kneading a resin composition containing a polyester resin (A) and a polylactic acid polymer (B) to obtain a melt, and subjecting the melt to a melt-blown method or a spunbond method to obtain a nonwoven fabric.

[0012] According to the present invention, a nonwoven fabric having excellent low heat shrinkage and extensibility, and a method for producing the same can be provided. Furthermore, according to the present invention, a nonwoven fabric having excellent productivity and a method for producing the same can be provided.

[0013] The following describes an embodiment of the present invention. However, the embodiment described below is merely an example for embodying the technical concept of the present invention, and the present invention is not limited to the following description. In this specification, preferred embodiments are shown, but a combination of two or more of the individual preferred embodiments is also a preferred embodiment. For matters indicated as numerical ranges, when there are several numerical ranges, the lower limit and upper limit can be selectively combined to form a preferred embodiment. Furthermore, when a numerical range is described as "XX to YY," it means "XX or more and YY or less." In this specification, "main chain" means the longest molecular chain in a molecule, unless otherwise specified. Furthermore, "branched chain" means a molecular chain other than the main chain in a molecule, unless otherwise specified.

[0014] [Nonwoven Fabric] The nonwoven fabric according to this embodiment is a nonwoven fabric comprising fibers formed from a resin composition containing a polyester resin (A) and a polylactic acid polymer (B), wherein the polyester resin (A) contains units derived from a polyhydric alcohol (a1) and units derived from a polycarboxylic acid (a2), and the polyhydric alcohol (a1) contains an aliphatic diol (a1-1) having 4 or more carbon atoms and having an alkyl group as a branched chain. The term "unit" refers to a "structural unit." The polyester resin (A) typically functions as a plasticizer for the polylactic acid polymer (B). Therefore, the polylactic acid polymer (B) is typically excluded from the polyester resin (A).

[0015] The nonwoven fabric according to this embodiment has excellent low thermal shrinkage and excellent elongation. In particular, the effect of excellent elongation is not achieved when a polyolefin resin, a type of known soft resin, is used, as illustrated in the Examples section, and should therefore be understood as a distinct effect achieved when a polyester resin (A) is used. The reason for this distinct effect in this embodiment is unclear, but one possible reason is that when a polyolefin resin is used, the polyolefin resin and the polylactic acid polymer (B) are incompatible, whereas when a polyester resin (A) is used, the polyester resin (A) and the polylactic acid polymer (B) each contain an ester structural unit and therefore have a moderate degree of compatibility with each other.

[0016] Furthermore, the polyester resin (A) contained in the resin composition capable of forming the nonwoven fabric according to this embodiment contains units derived from an aliphatic diol (a1-1) having 4 or more carbon atoms and having an alkyl group as a branched chain, and therefore the biodegradability of the polylactic acid polymer (B) is not significantly impaired, and the resulting nonwoven fabric tends to have excellent biodegradability. Furthermore, as illustrated in the Examples section, the nonwoven fabric according to this embodiment has good yield due to fewer defects that may occur locally, and as a result, has excellent productivity.

[0017] [Resin composition] A resin composition capable of forming the fibers constituting the nonwoven fabric according to this embodiment (hereinafter also referred to as the "resin composition according to this embodiment" or simply the "resin composition") will be described below. The resin composition according to this embodiment contains a polyester resin (A) and a polylactic acid polymer (B). The polyester resin (A) contains units derived from a polyhydric alcohol (a1) and units derived from a polycarboxylic acid (a2), and the polyhydric alcohol (a1) contains an aliphatic diol (a1-1) having 4 or more carbon atoms and having an alkyl group as a branched chain.

[0018] The melt mass flow rate (MFR) of the resin composition measured under conditions of a temperature of 190°C and a load of 2.16 kg is, from the viewpoint of reducing the diameter of the nonwoven fabric during production and improving low heat shrinkage and extensibility, preferably 10 g / 10 min or more, more preferably 30 g / 10 min or more, even more preferably 40 g / 10 min or more, still more preferably 50 g / 10 min or more, still more preferably 60 g / 10 min or more, still more preferably 66 g / 10 min or more, still more preferably 70 g / 10 min or more, still more preferably 75 g / 10 min or more, still more preferably 100 g / 10 min or more, and still more preferably 110 g / 10 min or more. The melt mass flow rate (MFR) of the resin composition measured under conditions of a temperature of 190°C and a load of 2.16 kg is preferably 300 g / 10 min or less, more preferably 250 g / 10 min or less, even more preferably 230 g / 10 min or less, still more preferably 210 g / 10 min or less, still more preferably 200 g / 10 min or less, and still more preferably 190 g / 10 min or less, from the viewpoint of suppressing yarn breakage in the melt spinning step. Specifically, the MFR can be measured by the method described in the Examples section.

[0019] <Polyester Resin (A)> The polyester resin (A) contains units derived from a polyhydric alcohol (a1) and units derived from a polycarboxylic acid (a2), and the polyhydric alcohol (a1) contains an aliphatic diol (a1-1) having 4 or more carbon atoms and having an alkyl group as a branched chain. The polyester resin (A) may contain multiple types of units derived from the polyhydric alcohol (a1). The polyester resin (A) may contain multiple types of units derived from the polycarboxylic acid (a2). Note that those skilled in the art can distinguish between units derived from the polycarboxylic acid (a2) contained in the polyester resin and units derived from polycaprolactone. The polyester resin (A) may or may not contain units derived from polycaprolactone. In one embodiment, the polyester resin (A) does not contain units derived from polycaprolactone.

[0020] The number of carboxy groups in the polycarboxylic acid (a2) is 2 or more, and preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less. In one embodiment, the polycarboxylic acid (a2) is a dicarboxylic acid.

[0021] <Polyhydric Alcohol (a1)> The polyhydric alcohol (a1) is a compound having two or more hydroxyl groups. The upper limit of the number of hydroxyl groups in the polyhydric alcohol (a1) is not limited as long as the intended effects of the present invention are not excessively impaired, and is, for example, 8 or less, 6 or less, or 4 or less.

[0022] As described above, the polyhydric alcohol (a1) includes an aliphatic diol (a1-1) having 4 or more carbon atoms and having an alkyl group as a branched chain (hereinafter, also simply referred to as "aliphatic diol (a1-1)").

[0023] (Aliphatic Diol (a1-1)) The aliphatic diol (a1-1) has a divalent aliphatic hydrocarbon group having 4 or more carbon atoms and two hydroxyl groups. The aliphatic diol (a1-1) has 4 or more carbon atoms and has a branched chain. That is, it is an aliphatic diol other than a linear diol terminated at both ends (α,ω-linear diol). The main chain of the aliphatic diol (a1-1) may be a molecular chain located between the two hydroxyl groups. Furthermore, the "branched chain" in the aliphatic diol (a1-1) usually refers to a partial structure branching from the "main chain" in the aliphatic diol (a1-1). The aliphatic diol (a1-1) may or may not have any branched chain other than a branched chain consisting of an alkyl group. Furthermore, the number of carbon atoms in the aliphatic diol (a1-1) is the sum of the number of carbon atoms in the main chain and the number of carbon atoms in the branched chain. When the polyhydric alcohol (a1) contains an aliphatic diol (a1-1) having 4 or more carbon atoms and an alkyl group as a branched chain, the biodegradability of the resulting nonwoven fabric tends to be improved.

[0024] In the aliphatic diol (a1-1), the number of branched chains consisting of alkyl groups is preferably one or two, more preferably one, from the viewpoints of biodegradability and improving low heat shrinkage and extensibility. Furthermore, from the same viewpoints, the branched chains are preferably methyl groups, ethyl groups, and propyl groups, more preferably methyl groups and ethyl groups, and even more preferably methyl groups. Furthermore, when the aliphatic diol (a1-1) has multiple branched chains, the respective branched chains may be the same or different. Furthermore, from the viewpoints of biodegradability and improving low heat shrinkage and extensibility, the branched chain is preferably bonded to a carbon atom between carbon atoms bonding to two hydroxyl groups.

[0025] From the viewpoint of biodegradability, the number of carbon atoms in the aliphatic diol (a1-1) is preferably 10 or less, more preferably 9 or less, even more preferably 8 or less, and still more preferably 7 or less. From the viewpoint of improving low heat shrinkage and extensibility, the number of carbon atoms in the aliphatic diol (a1-1) is 4 or more, preferably 5 or more, and more preferably 6 or more. From the viewpoint of improving biodegradability, low heat shrinkage and extensibility, the number of carbon atoms in the aliphatic diol (a1-1) is preferably 4 to 10, more preferably 5 to 10, even more preferably 6 to 9, still more preferably 6 to 8 or less, and still more preferably 6 to 7.

[0026] Examples of the aliphatic diol (a1-1) include 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-methyl-1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 2,3-pentanediol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 1,4-pentanediol, and 2-methyl-1,5-pentanediol. 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 2,5-hexanediol, 1,2-heptanediol, 1,2-octanediol, 2-ethyl-1,6-hexanediol, 1,2-nonanediol, 2-methyl-1,8-octanediol, and 1,2-decanediol. The aliphatic diol (a1-1) is preferably 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, or 2,4-diethyl-1,5-pentanediol, and more preferably 3-methyl-1,5-pentanediol. The aliphatic diol (a1-1) may be used alone or in combination of two or more.

[0027] In one embodiment, the content of units derived from the aliphatic diol (a1-1) in the units derived from the polyhydric alcohol (a1) is preferably 90 mol% or more, more preferably 95 mol% or more, even more preferably 99 mol% or more, and may be 100 mol%, from the viewpoint of improving low heat shrinkage and elongation. In a specific embodiment, the polyhydric alcohol (a1) is an aliphatic diol (a1-1). In another embodiment, the total amount of the aliphatic diol (a1-1) in the polyhydric alcohol (a1) may be less than 90 mol%.

[0028] The polyhydric alcohol (a1) may contain a polyhydric alcohol (a1-2) other than the aliphatic diol (a1-1). The polyhydric alcohol (a1-2) may be used singly or in combination of two or more. The polyhydric alcohol (a1-2) has two or more hydroxyl groups. The upper limit of the number of hydroxyl groups in the polyhydric alcohol (a1-2) is not limited as long as the intended effects of the present invention are not excessively impaired, but is, for example, 8 or less, 6 or less, or 4 or less. The polyhydric alcohol (a1-2) has 2 or more carbon atoms, preferably 16 or less. The polyhydric alcohol may also contain an ether bond. Examples of the polyhydric alcohol (a1-2) include diols having 3 or less carbon atoms, linear diols having 4 or more carbon atoms at both ends, and polyhydric alcohols having 3 or more hydroxyl groups.

[0029] Examples of the polyhydric alcohol (a1-2) include ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, dibutylene glycol, tributylene glycol, tetrabutylene glycol, trimethylolpropane, glycerin, erythritol, sorbitol, pentaerythritol, and dipentaerythritol.

[0030] In the polyester resin (A), from the viewpoint of improving low heat shrinkage and extensibility, the content of units derived from polyhydric alcohol (a1-2) in the units derived from polyhydric alcohol (a1) is preferably 10 mol % or less, more preferably 5 mol % or less, even more preferably 1 mol % or less, and even more preferably substantially 0 mol %. Here, "substantially 0 mol %" refers to the case where units derived from polyhydric alcohol (a1-2) are unintentionally contained, for example, the case where polyhydric alcohol (a1-2) is contained as an impurity in the raw material aliphatic diol (a1-1).

[0031] <Polycarboxylic Acid (a2)> The polycarboxylic acid (a2) is a compound having two or more carboxy groups. There are no limitations on the polycarboxylic acid (a2) as long as the effects of the present invention are not impaired. The upper limit of the number of carboxy groups in the polycarboxylic acid (a2) is not limited as long as the expected effects of the present invention are not excessively impaired, and is, for example, 8 or less, 6 or less, or 4 or less. From the viewpoint of improving low heat shrinkability and extensibility, the number of carboxy groups in the polycarboxylic acid (a2) is preferably 2 or more, and from the same viewpoint, it is preferably 8 or less, more preferably 6 or less, even more preferably 4 or less, and still more preferably 2.

[0032] Examples of the polycarboxylic acid (a2) include aliphatic dicarboxylic acids (a2-1), aromatic dicarboxylic acids (a2-2), and alicyclic dicarboxylic acids (a2-3). Among these, from the viewpoints of biodegradability and improving low heat shrinkage and extensibility, one or more selected from aliphatic dicarboxylic acids (a2-1) and alicyclic dicarboxylic acids (a2-3) are preferred, and aliphatic dicarboxylic acids (a2-1) are more preferred. Among the units derived from the polycarboxylic acid (a2), from the viewpoints of biodegradability and improving low heat shrinkage and extensibility, the content of units derived from one or more selected from aliphatic dicarboxylic acids (a2-1) and alicyclic dicarboxylic acids (a2-3) is preferably 50 mol% or more, more preferably 75 mol% or more, even more preferably 90 mol% or more, and may even be 100 mol%. Furthermore, from the viewpoints of biodegradability and improving low heat shrinkage and extensibility, the content of units derived from aliphatic dicarboxylic acid (a2-1) in the units derived from polycarboxylic acid (a2) is preferably 50 mol % or more, more preferably 75 mol % or more, even more preferably 90 mol % or more, and even more preferably substantially 100 mol %. Here, "substantially 100 mol %" refers to the case where a polycarboxylic acid other than aliphatic dicarboxylic acid (a2-1) is unintentionally contained, for example, the case where a polycarboxylic acid other than aliphatic dicarboxylic acid (a2-1) is contained in the raw material aliphatic dicarboxylic acid (a2-1).

[0033] In one embodiment, the polycarboxylic acid (a2) is an aliphatic dicarboxylic acid (a2-1). From the viewpoint of heat resistance, the polycarboxylic acid (a2) may contain an aromatic dicarboxylic acid (a2-2). From the viewpoint of biodegradability and improving low heat shrinkage and extensibility, the content of units derived from aromatic dicarboxylic acid (a2-2) in the units derived from the polycarboxylic acid (a2) is preferably 50 mol% or less, more preferably 25 mol% or less, even more preferably 10 mol% or less, and may even be 0 mol%.

[0034] From the viewpoint of exhibiting good extensibility, the number of carbon atoms in the polycarboxylic acid (a2) is preferably 4 or more, more preferably 5 or more, and even more preferably 6 or more. From the viewpoint of exhibiting even better biodegradability and improving low heat shrinkage and extensibility, the number of carbon atoms in the polycarboxylic acid (a2) is preferably 12 or less, more preferably 10 or less, and even more preferably 8 or less. That is, the number of carbon atoms in the polycarboxylic acid (a2) is preferably 4 to 12, more preferably 5 to 10, and even more preferably 6 to 10. The number of carbon atoms in the polycarboxylic acid (a2) is the sum of the number of carbon atoms in the carboxy groups and the number of carbon atoms in the moieties other than the carboxy groups. Furthermore, the preferred embodiment of the number of carbon atoms in the aliphatic dicarboxylic acid (a2-1) is the same as above.

[0035] Examples of the aliphatic dicarboxylic acid (a2-1) include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, decanedicarboxylic acid, dodecylsuccinic acid, dodecenylsuccinic acid, octenylsuccinic acid, maleic acid, and fumaric acid. From the viewpoint of improving low heat shrinkage and elongation, the aliphatic dicarboxylic acid (a2-1) is preferably at least one selected from adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. In a specific embodiment, the aliphatic dicarboxylic acid (a2-1) is at least one of adipic acid and sebacic acid, preferably adipic acid or sebacic acid. One aliphatic dicarboxylic acid (a2-1) may be used alone, or two or more may be used in combination.

[0036] Examples of the aromatic dicarboxylic acid (a2-2) include phthalic acid, terephthalic acid, isophthalic acid, diphenic acid, 4,4'-biphenyldicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 2,3-furandicarboxylic acid, 2,4-furandicarboxylic acid, 2,5-furandicarboxylic acid, and 3,4-furandicarboxylic acid. From the viewpoint of heat resistance, the aromatic dicarboxylic acid (a2-2) is preferably at least one selected from terephthalic acid and isophthalic acid. The aromatic dicarboxylic acid (a2-2) may be used alone or in combination of two or more kinds.

[0037] Examples of the alicyclic dicarboxylic acid (a2-3) include 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, cycloheptanedicarboxylic acid, cyclooctanedicarboxylic acid, cyclodecanedicarboxylic acid, decahydro-1,4-naphthalenedicarboxylic acid, 1,3-adamantanedicarboxylic acid, etc. The alicyclic dicarboxylic acid (a2-3) may be used alone or in combination of two or more.

[0038] (Ratio of (a1) / (a2)) From the viewpoint of making the terminal groups of the polyester resin (A) hydroxyl groups, it is preferable that the content (mol) of units derived from the polyhydric alcohol (a1) is greater than the content (mol) of units derived from the polycarboxylic acid (a2). This can be adjusted by the charge ratio when preparing the resin composition. From the same viewpoint, the ratio (molar ratio) of the content of units derived from the polyhydric alcohol (a1) to the content of units derived from the polycarboxylic acid (a2) is preferably more than 50 / less than 50 to 75 / 25, more preferably 50.5 / 49.5 to 75 / 25, and even more preferably 51 / 49 to 70 / 30. The molar ratio can be determined by the method described in the Examples section.

[0039] From the viewpoint of making the terminal groups of the polyester resin (A) hydroxyl groups, it is preferable that the total number of hydroxyl groups in the units derived from the polyhydric alcohol (a1) is greater than the total number of carboxyl groups in the units derived from the polycarboxylic acid (a2). This can be adjusted by the charging ratio of raw materials when producing the polyester resin (A). From the same viewpoint, the ratio of the total number of hydroxyl groups in the units derived from the polyhydric alcohol (a1) to the total number of carboxyl groups in the units derived from the polycarboxylic acid (a2) is preferably more than 50 / less than 50 to 75 / 25, more preferably 50.5 / 49.5 to 75 / 25, and even more preferably 51 / 49 to 70 / 30. The number of hydroxyl groups and the number of carboxyl groups can be determined by the method described in the Examples section.

[0040] From the same viewpoint, when the polyester resin (A) is composed of units derived from an aliphatic diol (a1-1) and an aliphatic dicarboxylic acid (a2-1), it is preferable that the content (mol) of units derived from the aliphatic diol (a1-1) is greater than the content (mol) of units derived from the aliphatic dicarboxylic acid (a2-1). This can also be adjusted by the feed ratio of the raw materials used in producing the polyester resin (A). From the same viewpoint, the ratio (molar ratio) of the content of units derived from the polyhydric alcohol (a1) to the content of units derived from the polycarboxylic acid (a2) is preferably greater than 50 / less than 50 to 75 / 25, more preferably 50.5 / 49.5 to 75 / 25, and even more preferably 51 / 49 to 70 / 30. The molar ratio can be determined by the method described in the Examples section.

[0041] As a combination of the polyhydric alcohol (a1) and the polycarboxylic acid (a2), from the viewpoint of improving low heat shrinkage and elongation, for example, a combination of at least one selected from the group consisting of 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and 2,4-diethyl-1,5-pentanediol with at least one selected from the group consisting of adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid is an example of a preferred embodiment, and examples of the combination include a combination of 2-methyl-1,3-propanediol and adipic acid, a combination of 3-methyl-1,5-pentanediol and adipic acid, a combination of 2,4-diethyl-1,5-pentanediol and adipic acid, a combination of 2-methyl-1,3-propanediol and pimelic acid, and a combination of 3-methyl-1,5-pentanediol and adipic acid. More preferred embodiments include a combination of 3-methyl-1,5-pentanediol and pimelic acid, a combination of 2,4-diethyl-1,5-pentanediol and sebacic acid, and a combination of 2,4-diethyl-1,5-pentanediol and sebacic acid. Further preferred embodiments include a combination of 3-methyl-1,5-pentanediol and adipic acid, a combination of 2,4-diethyl-1,5-pentanediol and adipic acid, a combination of 3-methyl-1,5-pentanediol and pimelic acid, a combination of 3-methyl-1,5-pentanediol and sebacic acid, and a combination of 2,4-diethyl-1,5-pentanediol and pimelic acid. Further preferred embodiments include a combination of 3-methyl-1,5-pentanediol and adipic acid, and a combination of 3-methyl-1,5-pentanediol and sebacic acid.

[0042] The polyester resin (A) may or may not contain a unit (a') other than the unit derived from the polyhydric alcohol (a1) and the unit derived from the polycarboxylic acid (a2). The monomer constituting the unit (a') is not particularly limited as long as it does not impair the effects of the present invention.

[0043] A first example of the monomer constituting the unit (a') is a monomer copolymerizable with at least one of the polyhydric alcohol (a1) and the polycarboxylic acid (a2). The molecular weight of the copolymerizable monomer is preferably 300 or less. Specific examples include polyhydric phenols, such as catechol, resorcinol, and bisphenol A.

[0044] Second examples of the monomer constituting the unit (a') include a terminal functionalizing agent and a terminal blocking agent. Here, the two or more terminal groups of the polymer constituting the polyester resin (A) are usually either hydroxyl groups or carboxyl groups derived from the polyhydric alcohol (a1) and the polycarboxylic acid (a2), and in one embodiment, the polyester resin (A) is a polyester diol. The terminal functionalizing agent and the terminal blocking agent react with the hydroxyl groups or carboxyl groups that are the terminal groups of the polyester resin (A), and as a result, the terminal groups of the polyester resin (A) contain groups derived from the terminal functionalizing agent and the terminal blocking agent. Therefore, in another embodiment, at least one of the two or more terminal groups of the polyester resin (A) is preferably -COR ａ (R ａ is an alkyl group having 1 to 12 carbon atoms, or an acyl group represented by —OCOR ｂ (R ｂ is an alkyl group having 1 to 12 carbon atoms. ) is an acyloxy group represented by the formula: The molecular weight of the compound constituting the terminal functionalizing agent and the terminal blocking agent is preferably 300 or less. Specific examples include monovalent aliphatic carboxylic acids, such as acetic acid, propionic acid, hexanoic acid, caprylic acid, 2-ethylhexanoic acid, capric acid, and lauric acid.

[0045] From the viewpoint of improving low heat shrinkage and extensibility, the content of units (a') in polyester resin (A) is preferably 50 mol% or less, more preferably 30 mol% or less, even more preferably 20 mol% or less, still more preferably 15 mol% or less, and particularly preferably 10 mol% or less. From the viewpoint of improving low heat shrinkage and extensibility, the total content of units derived from polyhydric alcohol (a1) and units derived from polycarboxylic acid (a2) in polyester resin (A) is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, still more preferably 85 mol% or more, particularly preferably 90 mol% or more, and may even be 100 mol%.

[0046] <Number Average Molecular Weight of Polyester Resin (A)> From the viewpoints of heat shrinkability and extensibility, the number average molecular weight of the polyester resin (A) is preferably 500 or more, more preferably 1,000 or more, even more preferably 1,500 or more, still more preferably 2,000 or more, and still more preferably 2,500 or more. From the viewpoints of moldability and compatibility with the polylactic acid polymer (B), the number average molecular weight of the polyester resin (A) is preferably 100,000 or less, more preferably 50,000 or less, even more preferably 20,000 or less, still more preferably 10,000 or less, and still more preferably 5,000 or less.

[0047] In one embodiment of the present invention, the number average molecular weight of the polyester resin (A) is preferably 500 to 100,000, more preferably 1,000 to 100,000, even more preferably 1,500 to 50,000, still more preferably 2,000 to 20,000, still more preferably 2,000 to 10,000, and still more preferably 2,000 to 5,000, from the viewpoints of heat shrinkability and extensibility, moldability, and compatibility with the polylactic acid polymer (B).

[0048] The number average molecular weight of the polyester resin (A) can be determined by gel permeation chromatography (GPC) in terms of standard polystyrene. When a commercially available product is used, the value listed in the catalog may be used.

[0049] In one aspect of the present invention, from the viewpoint of improving low heat shrinkage and extensibility, preferably, the polycarboxylic acid (a2) is an aliphatic dicarboxylic acid (a2-1), the aliphatic dicarboxylic acid (a2-1) includes adipic acid, and the number average molecular weight of the polyester resin (A) is preferably 500 to 100,000, more preferably 1,000 to 100,000, even more preferably 2,000 to 100,000, still more preferably 2,000 to 10,000, and still more preferably 2,000 to 5,000.

[0050] In another aspect of the present invention, from the viewpoint of improving low heat shrinkage and extensibility, preferably, the polyvalent carboxylic acid (a2) is an aliphatic dicarboxylic acid (a2-1), the aliphatic dicarboxylic acid (a2-1) includes sebacic acid, and the number average molecular weight of the polyester resin (A) is 500 to 100,000, more preferably 1,000 to 100,000, even more preferably 2,000 to 100,000, still more preferably 2,000 to 10,000, and still more preferably 2,000 to 5,000.

[0051] <<Method for Producing Polyester Resin (A)>> The polyester resin (A) can be produced by a conventional method. For example, it can be produced by subjecting a polyhydric alcohol (a1) and a polycarboxylic acid (a2) to a polycondensation reaction, preferably in the presence of a catalyst, at a temperature of 150 to 250°C. From the viewpoint of the efficiency of the condensation polymerization reaction, preferred catalysts include tin compounds and titanium compounds, and preferred catalysts include tin di(2-ethylhexanoate), dibutyltin oxide, and tetraisopropyl titanate.

[0052] <Polylactic Acid Polymer (B)> Examples of the polylactic acid polymer (B) used in this embodiment include at least one selected from the group consisting of a homopolymer of L-lactic acid, a homopolymer of D-lactic acid, a copolymer of L-lactic acid and D-lactic acid, a homopolymer of DL-lactic acid, a copolymer of DL-lactic acid and L-lactic acid, a copolymer of DL-lactic acid and D-lactic acid, and a polymer of lactide, which is a cyclic dimer of lactic acid.

[0053] The polylactic acid polymer (B) may also be a copolymer of lactic acid with an aliphatic hydroxycarboxylic acid other than lactic acid, an aliphatic dicarboxylic acid, an aliphatic diol, an aromatic dicarboxylic acid, etc. The copolymer preferably contains 70 mol % or more, more preferably 90 mol % or more, of units derived from lactic acid.

[0054] Among these, from the viewpoints of strength and heat resistance, the polylactic acid polymer (B) is preferably a homopolymer of L-lactic acid, a homopolymer of D-lactic acid, or a copolymer of L-lactic acid and D-lactic acid, with a homopolymer of L-lactic acid being more preferred. When the polylactic acid polymer (B) contains units derived from D-lactic acid, from the viewpoint of low heat shrinkage, the content of units derived from D-lactic acid in the polylactic acid polymer (B) is preferably 40 mol% or less, more preferably 30 mol% or less, even more preferably 20 mol% or less, and even more preferably 10 mol% or less. When the polylactic acid polymer (B) contains units derived from L-lactic acid, from the viewpoint of low heat shrinkage, the content of units derived from L-lactic acid in the polylactic acid polymer (B) is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, still more preferably 90 mol% or more, and even more preferably 98 mol% or more. The polylactic acid polymer (B) may be used alone or in combination of two or more kinds.

[0055] Commercially available polylactic acid polymers (B) may be used, such as those available under the trade name "Ingeo series" from NatureWorks, those available under the trade name "Luminy series" from Total Energies Corbion, those available under the trade name "Revode" from Zhejiang Hisun Biomaterials Co., Ltd., and those available under the trade name "SUPLA" from SUPLA Material Technology Co., Ltd.

[0056] The melt mass flow rate (MFR) of the polylactic acid polymer (B), measured under conditions of a temperature of 190°C and a load of 2.16 kg, is preferably 3 g / 10 min or more, more preferably 10 g / 10 min or more, and even more preferably 20 g / 10 min or more from the viewpoint of reducing the diameter of the nonwoven fabric during production, and is preferably 80 g / 10 min or less, more preferably 60 g / 10 min or less, and even more preferably 40 g / 10 min or less from the viewpoint of suppressing yarn breakage during the melt spinning step. The MFR can be measured in accordance with JIS K 7210-1:2014 using a commercially available measuring device.

[0057] The crystallization exothermic peak temperature Tc(B) of the polylactic acid polymer (B) is not particularly limited, but is generally in the range of 85° C. to 120° C. The crystallization exothermic peak temperature Tc(B) of the polylactic acid polymer (B) can be measured in accordance with JIS K7121:2012 using a commercially available differential scanning calorimeter, by producing a nonwoven fabric from the polylactic acid polymer (B) as a test piece.

[0058] <Cyclic Ester Compound (C)> The resin composition in this embodiment may further contain a cyclic ester compound (C). By including the cyclic ester compound (C), the glass transition temperature of the kneaded product of the resin composition in this embodiment tends to be increased, while if the content of the cyclic ester compound (C) is too high, the glass transition temperature will be decreased. From the viewpoint of more reliably increasing the glass transition temperature and from the viewpoint of low thermal shrinkage, the amount of the cyclic ester compound (C) is preferably less than 30% by mass, more preferably 25% by mass or less, even more preferably 15% by mass or less, even more preferably 5% by mass or less, and even more preferably 3% by mass or less, relative to 100% by mass of the polyester resin (A).

[0059] The cyclic ester compound (C) is not particularly limited, and may be a cyclized product of a hydroxycarboxylic acid such as an intermolecular cyclic ester of an α-hydroxycarboxylic acid, a γ-hydroxycarboxylic acid, a 3-hydroxycarboxylic acid, or the like; a condensed cyclized product of an alcohol such as a lactone and a carboxylic acid; or another cyclic compound having an ester structure.

[0060] Examples of α-hydroxycarboxylic acids that form intermolecular cyclic esters include glycolic acid, L- and / or D-lactic acid, α-hydroxybutyric acid, α-hydroxyisobutyric acid, α-hydroxyvaleric acid, α-hydroxycaproic acid, α-hydroxyisocaproic acid, α-hydroxyheptanoic acid, α-hydroxyoctanoic acid, α-hydroxydecanoic acid, α-hydroxymyristic acid, α-hydroxystearic acid, and alkyl-substituted derivatives thereof.

[0061] Examples of lactones include β-propiolactone, β-butyrolactone, pivalolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, and ε-caprolactone.

[0062] Other examples of cyclic compounds having an ester structure include dioxanones such as trimethylene carbonate, etc. When the cyclic ester has an asymmetric carbon, it may be in the D-form, L-form, or racemic form.

[0063] These cyclic esters can be used either alone or in combination of two or more.

[0064] From the viewpoint of increasing the glass transition temperature of the kneaded resin composition, the cyclic ester compound (C) preferably contains units derived from an aliphatic diol (c1) and an aliphatic dicarboxylic acid (c2), i.e., is preferably a cyclic ester compound obtained by reacting an aliphatic diol (c1) with an aliphatic dicarboxylic acid (c2).

[0065] The aliphatic diol (c1) is not particularly limited, but examples thereof include the same aliphatic diols as the above-mentioned aliphatic diol (a1-1).

[0066] The aliphatic dicarboxylic acid (c2) is not particularly limited, but examples thereof include the same as the above aliphatic dicarboxylic acid (a2-1).

[0067] As a combination of the aliphatic diol (c1) and the aliphatic dicarboxylic acid (c2), from the viewpoint of increasing the glass transition temperature of the kneaded product of the resin composition, a combination of at least one selected from the group consisting of 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and 2,4-diethyl-1,5-pentanediol with at least one selected from the group consisting of adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid is an example of a preferred embodiment, and examples thereof include a combination of 2-methyl-1,3-propanediol and adipic acid, a combination of 3-methyl-1,5-pentanediol and adipic acid, a combination of 2,4-diethyl-1,5-pentanediol and adipic acid, a combination of 2-methyl-1,3-propanediol and pimelic acid, and a combination of 3-methyl-1,5-pentanediol and sebacic acid. More preferred embodiments include a combination of 3-methyl-1,5-pentanediol and pimelic acid, a combination of 3-methyl-1,5-pentanediol and sebacic acid, and a combination of 2,4-diethyl-1,5-pentanediol and sebacic acid. Further preferred embodiments include a combination of 3-methyl-1,5-pentanediol and adipic acid, a combination of 2,4-diethyl-1,5-pentanediol and adipic acid, a combination of 3-methyl-1,5-pentanediol and pimelic acid, a combination of 3-methyl-1,5-pentanediol and sebacic acid, and a combination of 2,4-diethyl-1,5-pentanediol and pimelic acid. Further preferred embodiments include a combination of 3-methyl-1,5-pentanediol and adipic acid, and a combination of 3-methyl-1,5-pentanediol and sebacic acid.

[0068] From the viewpoint of increasing the glass transition temperature of the kneaded resin composition, the cyclic ester compound (C) containing units derived from the aliphatic diol (c1) and the aliphatic dicarboxylic acid (c2) is preferably a cyclic ester compound (4-methyl-1,7-dioxacyclotridecane-8,13-dione) obtained by reacting 3-methyl-1,5-pentanediol with adipic acid.

[0069] The method for producing the cyclic ester compound (C) is not particularly limited, but it can be produced by a known condensation reaction using a hydroxycarboxylic acid or an alcohol and a carboxylic acid as raw materials.

[0070] <Content Ratio> From the viewpoint of improving low heat shrinkage and extensibility, the resin composition in this embodiment contains preferably 0.1 to 50 parts by mass, more preferably 1 to 40 parts by mass, even more preferably 3 to 40 parts by mass, still more preferably 3 to 35 parts by mass, still more preferably 9 to 27 parts by mass, and even more preferably 12 to 22 parts by mass of the polyester resin (A) per 100 parts by mass of the polylactic acid polymer (B). From the viewpoint of further improving the extensibility of the nonwoven fabric, the resin composition contains preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and even more preferably 9 parts by mass or more of the polyester resin (A) per 100 parts by mass of the polylactic acid polymer (B).

[0071] In addition, from the viewpoint of improving low heat shrinkage and extensibility, the total content of the polyester resin (A) and the polylactic acid polymer (B) in the resin composition in this embodiment is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, and even more preferably 98% by mass or more, and may be 100% by mass. With this content ratio, the effects of the present invention are more significantly exhibited.

[0072] When the resin composition in this embodiment further contains a cyclic ester compound (C) in addition to the polyester resin (A) and the polylactic acid polymer (B), the cyclic ester compound (C) is preferably contained in an amount of 0.001 to 3.0 parts by mass, more preferably 0.005 to 2.5 parts by mass, even more preferably 0.01 to 2.0 parts by mass, still more preferably 0.01 to 1.5 parts by mass, still more preferably 0.01 to 1.0 part by mass, still more preferably 0.01 to 0.5 parts by mass, and still more preferably 0.01 to 0.1 parts by mass, relative to 100 parts by mass of the polylactic acid polymer (B).

[0073] The resin composition in this embodiment may contain at least one resin component selected from the group consisting of biomass resins and biodegradable resins other than the polyester resin (A), the polylactic acid polymer (B), and the cyclic ester compound (C).

[0074] Examples of such biomass resins or biodegradable resins include polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT), polyglycolic acid (PGA), polyethylene furanoate (PEF), polyhydroxyalkanoate (PHA) [e.g., polyhydroxybutyrate (PHB), polyhydroxybutyrate valerate (PHBV), 3-hydroxybutyric acid-3-hydroxyhexanoic acid copolymer polyester, etc.], cellulose acetate (CA), and starch polyester (Mater-Bi (registered trademark)).

[0075] As long as the intended effects of the present invention are not excessively impaired, the resin composition in this embodiment may or may not contain resin components other than the polyester resin (A), polylactic acid polymer (B), cyclic ester compound (C), biomass resin, and biodegradable resin. Examples of such resin components include polyolefin resins (e.g., polypropylene resins). The polyolefin resin may be a polypropylene resin having a melt mass flow rate (MFR) of less than 250 g / 10 min measured at a temperature of 230°C and a load of 2.16 kg, or a polypropylene resin having an MFR (230°C, 2.16 kg) of 250 g / 10 min or more. When the resin composition in this embodiment contains resin components other than the polyester resin (A), polylactic acid polymer (B), cyclic ester compound (C), biomass resin, and biodegradable resin, the content of the resin components is preferably 5% by mass or less, more preferably 3% by mass or less, and more preferably 1% by mass or less, from the viewpoint of improving low heat shrinkage and elongation. In a specific embodiment, the resin composition does not contain a polyolefin-based resin, and preferably does not contain any resin components other than the polyester-based resin (A), the polylactic acid-based polymer (B), the cyclic ester compound (C), the biomass resin, and the biodegradable resin.

[0076] <Additives> The resin composition in this embodiment may contain additives other than the polyester resin (A) and the polylactic acid polymer (B). Examples of additives include inorganic fillers, softeners, heat aging inhibitors, antioxidants, hydrolysis resistance inhibitors, light stabilizers, antistatic agents, release agents, flame retardants, foaming agents, pigments, dyes, brighteners, UV absorbers, lubricants, and impact modifiers. These may be used alone or in combination of two or more. When using the above additives, the content of the additives in the resin composition may be appropriately determined depending on the desired physical properties of the resin composition.

[0077] <Method for producing resin composition> There are no particular limitations on the method for producing the resin composition in this embodiment, and it is sufficient to uniformly mix the polyester resin (A), the polylactic acid polymer (B), and, if necessary, the cyclic ester compound (C) and additives.

[0078] Examples of the mixing method include a method of melt-kneading using a single-screw extruder, a multi-screw extruder, a Banbury mixer, a heated roll, a Brabender, various kneaders, etc., or a method of feeding each component through a separate inlet and melt-kneading the components.

[0079] Alternatively, preblending may be carried out before melt-kneading. Examples of preblending methods include methods using a mixer such as a Henschel mixer, a high-speed mixer, a V-blender, a ribbon blender, a tumbler blender, or a conical blender. The temperature during melt-kneading can be arbitrarily selected, preferably within the range of 140 to 250°C, taking into consideration the melting point and decomposition temperature of the polyester resin (A).

[0080] For example, a nonwoven fabric can be provided by forming the molded product into a fibrous body. Before forming the fibrous body, the molded product may or may not be shaped into strands, pellets, sheets, rods, particles, or the like.

[0081] [Physical Properties of Nonwoven Fabric] (Basis Weight) The basis weight of the nonwoven fabric according to this embodiment is not particularly limited, but is preferably adjusted depending on the application. ２ and may be in the range of 1 to 300 g / m ２and may be in the range of 2 to 200 g / m ２ and may be in the range of 5 to 100 g / m ２ and may be in the range of 10 to 30 g / m ２ The basis weight of the nonwoven fabric can be measured in accordance with JIS L 1096:2020. Specifically, the basis weight of the nonwoven fabric can be measured by the method described in the Examples section.

[0082] (Thickness) The thickness of the nonwoven fabric according to this embodiment is not particularly limited, but is preferably adjusted depending on the intended use. The thickness of the nonwoven fabric may be within the range of 0.001 to 10 mm, 0.001 to 5 mm, or 0.001 to 3 mm. According to the present invention, the diameter of the fibers that can form the nonwoven fabric can be reduced, thereby making it possible to reduce the thickness of the nonwoven fabric. In a preferred embodiment, the thickness of the nonwoven fabric is preferably within the range of 0.001 to 3 mm, more preferably within the range of 0.001 to 2 mm, even more preferably within the range of 0.01 to 1 mm, and even more preferably within the range of 0.05 to 0.3 mm. The thickness of the nonwoven fabric under standard conditions can be measured using a commercially available thickness measuring device. Specifically, the thickness of the nonwoven fabric can be measured using the method described in the Examples section.

[0083] (Air Permeability) In one aspect of the present embodiment, a nonwoven fabric having low air permeability can be produced by using a meltblown method. In this case, the nonwoven fabric preferably has an air permeability of 150 cm or less as measured in accordance with the Frazier method of JIS L 1913:2010 "General Nonwoven Fabric Testing Methods." ３ / (cm ２ s) or less, more preferably 125 cm ３ / (cm ２ s), more preferably less than 120 cm ３ / (cm ２ s), and even more preferably less than 100 cm ３ / (cm ２According to the present invention, it is possible to reduce the diameter of the fibers that can form the nonwoven fabric, so in a preferred embodiment, the breathability of the nonwoven fabric is preferably 90 cm3 / (cm2·s) or less, more preferably 80 cm3 / (cm2·s) or less. ３ / (cm ２ The lower limit of the breathability of the nonwoven fabric is naturally determined depending on the average fiber diameter of the fibers that can form the nonwoven fabric. ３ / (cm ２ ・s) or more, 15cm ３ / (cm ２ ・s) or more, 25cm ３ / (cm ２ ・s) or more, 50cm ３ / (cm ２ ・s) or more, or 60 cm ３ / (cm ２ ・s) or more may be used.

[0084] In another embodiment, a nonwoven fabric having low breathability can be produced by using a spunbond method. In this case, the lower limit of the breathability of the nonwoven fabric is preferably 100 cm ３ / (cm ２ s) or more, more preferably 150 cm ３ / (cm ２ s) or more, more preferably 200 cm ３ / (cm ２ The upper limit of the breathability of the nonwoven fabric is naturally determined depending on the basis weight of the nonwoven fabric and the average fiber diameter of the fibers that can form the nonwoven fabric. ３ / (cm ２ ・s) below, 450cm ３ / (cm ２ s) or less, or 400 cm ３ / (cm ２ ・s) or less may be used.

[0085] (Crystallization exothermic peak temperature) The nonwoven fabric according to this embodiment tends to have the characteristic of a low crystallization exothermic peak temperature. Specifically, the nonwoven fabric according to this embodiment has a crystallization exothermic peak temperature Tc of preferably 90°C or less, more preferably 85°C or less, and even more preferably 80°C or less. The lower limit of the crystallization exothermic peak temperature Tc is naturally determined depending on the composition of the resin composition used, but may be, for example, 50°C or more, 55°C or more, or 60°C or more. The crystallization exothermic peak temperature Tc can be measured in accordance with JIS K7121:2012 using a commercially available differential scanning calorimeter. Specifically, the crystallization exothermic peak temperature Tc can be measured using the method described in the Examples section.

[0086] (Low Heat Shrinkage) The nonwoven fabric according to this embodiment has excellent low heat shrinkage properties. The reason for this low heat shrinkage is believed to be that the aliphatic diol (a1) contained in the polyester resin (A) contributes to improved amorphousness and a lower glass transition temperature, thereby realizing stress relaxation during nonwoven fabric production and reducing residual stress. Low heat shrinkage can be evaluated, for example, by dry heat shrinkage (%). Specifically, the dry heat shrinkage of the nonwoven fabric according to this embodiment is preferably 11% or less, more preferably 10% or less, even more preferably 9% or less, and even more preferably 8% or less. The lower limit of the dry heat shrinkage is naturally determined depending on the composition of the resin composition used, but may be, for example, greater than 0%. The dry heat shrinkage can be determined by measuring the dimensions of the nonwoven fabric before and after heating, preferably at 100°C, and converting the ratio of the two values ​​into a percentage. Specifically, the dry heat shrinkage can be measured using the method described in the Examples section.

[0087] The nonwoven fabric according to this embodiment preferably has small anisotropy of low heat shrinkage in the plane of the nonwoven fabric, although this depends on the manufacturing method, etc. The absolute value of the difference between the dry heat shrinkage percentage (%) in the length direction and the dry heat shrinkage percentage (%) in the width direction of the nonwoven fabric according to this embodiment is preferably within 5%, more preferably within 4%, and even more preferably within 3%.

[0088] (Extensibility) The nonwoven fabric according to this embodiment has excellent extensibility. The excellent extensibility is thought to be due to the excellent compatibility between the polyester resin (A) and the polylactic acid polymer (B). Extensibility can be evaluated, for example, by the standard elongation (%). Specifically, the standard elongation of the nonwoven fabric according to this embodiment is preferably 8% or more, more preferably 10% or more, even more preferably 20% or more, and even more preferably 25% or more. The upper limit of the elongation is naturally determined depending on the composition of the resin composition used, but may be, for example, 90% or less, 80% or less, 70% or less, or 60% or less. The standard elongation can be measured in accordance with JIS L 1913:2010 "General Nonwoven Fabric Testing Methods." Specifically, the dry heat shrinkage can be measured using the method described in the Examples section.

[0089] The nonwoven fabric according to this embodiment may or may not have anisotropy in its in-plane extensibility, depending on its manufacturing method, etc. The absolute value of the difference between the standard elongation percentage (%) in the length direction and the standard elongation percentage (%) in the width direction of the nonwoven fabric according to this embodiment is preferably within 30%, more preferably within 25%, and even more preferably within 20%.

[0090] (Biodegradability) The nonwoven fabric according to this embodiment tends to have excellent biodegradability. Qualitatively, biodegradability can be evaluated using a polylactic acid-based nonwoven fabric containing fibers formed from fibers made of polylactic acid-based polymer (B) as a standard. The resin composition used in the nonwoven fabric according to this embodiment contains a polyester-based resin (A), which is more biodegradable than a polyolefin-based resin. Furthermore, the resin composition used in the nonwoven fabric according to this embodiment does not contain a polyolefin-based resin, which is generally known to have poor biodegradability, or if it does contain one, the content is small, so that the excellent biodegradability of polylactic acid-based nonwoven fabrics tends to be maintained.

[0091] <Additives> The nonwoven fabric according to this embodiment may contain additives in addition to the fibers formed from the resin composition in the above-described embodiment.

[0092] Examples of additives include inorganic fillers, softeners, heat aging inhibitors, antioxidants, hydrolysis resistance inhibitors, light stabilizers, antistatic agents, release agents, flame retardants, foaming agents, pigments, dyes, brighteners, ultraviolet absorbers, lubricants, impact resistance improvers, fibers other than the fibers formed from the resin compositions in the above-described embodiments, etc. These may be used alone or in combination of two or more.

[0093] When the above-mentioned additives are used, the content of the additives in the nonwoven fabric may be appropriately determined depending on the desired physical properties of the nonwoven fabric. The content of the additives in the nonwoven fabric according to this embodiment may be, for example, 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, 5% by mass or less, or even 0% by mass. The content of the fibers formed from the resin composition in the above-mentioned embodiment in the nonwoven fabric according to this embodiment may be, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or even 100% by mass.

[0094] <Composite> The nonwoven fabric according to this embodiment may or may not constitute a composite, such as a laminate, together with any substrate (e.g., another nonwoven fabric, a sheet material other than a nonwoven fabric). The formation of the composite usually involves heating and stretching, and the effects of the nonwoven fabric according to this embodiment are enjoyed, so a nonwoven fabric that is part of such a composite is also an example of this embodiment.

[0095] [Method for manufacturing nonwoven fabric] The nonwoven fabric according to the above-described embodiment can be obtained by, for example, a known method for manufacturing a nonwoven fabric. As illustrated in the Examples section, the nonwoven fabric according to the above-described embodiment has excellent low thermal shrinkage properties and excellent elongation, and therefore, according to the present invention, a method for manufacturing a nonwoven fabric having excellent low thermal shrinkage properties and excellent elongation can be provided.

[0096] Furthermore, as illustrated in the Examples section, the nonwoven fabric according to the above-described embodiment has excellent productivity, and therefore, according to the present invention, a method for producing a nonwoven fabric with excellent productivity can be provided.

[0097] In a specific aspect, a method for producing a nonwoven fabric includes a step of melt-kneading a resin composition containing a polyester resin (A) and a polylactic acid polymer (B) to obtain a melt, and a step of melt-blown or spunbonding the melt to obtain a nonwoven fabric, and these steps are used to produce the nonwoven fabric according to the above-mentioned embodiment. This can improve spinning stability, thereby providing a method for producing a nonwoven fabric with higher productivity. From the viewpoint of reducing the diameter of the fibers, the method for producing a nonwoven fabric according to a specific aspect preferably includes a step of obtaining a nonwoven fabric by the melt-blown method.

[0098] (Meltblown method) In the meltblown method, a nonwoven fabric can be produced by supplying the resin composition used for the nonwoven fabric according to the embodiment described above to a meltblown nonwoven fabric production apparatus. The produced nonwoven fabric is collected on the collection surface of a conveyor, preferably a net conveyor, installed near the meltblown nonwoven fabric production apparatus. Note that such a conveyor may be part of the meltblown nonwoven fabric production apparatus.

[0099] An example of the manufacturing process in a meltblown nonwoven fabric manufacturing apparatus will be described. A resin composition containing a polyester resin (A) and a polylactic acid polymer (B) supplied to the meltblown nonwoven fabric manufacturing apparatus is melt-kneaded in an extruder at a temperature ranging from 180°C to 250°C, for example, to form a melt. This melt is supplied to a die and subsequently discharged through a number of nozzles (spinning holes) formed in the die. This results in the melt becoming fibrous. The fibrous melt is exposed to hot air blown from a blower, for example, at a temperature ranging from 230°C to 350°C and at a flow rate ranging from 0.5 to 35 m / min, preferably 0.5 to 25 m / min, and more preferably 0.5 to 18 m / min. This achieves further diameter reduction of the melt. The diameter-reduced melt is collected on the collection surface of a conveyor as a nonwoven fabric. The collected nonwoven fabric may further undergo a process such as thermocompression bonding.

[0100] (Spunbond Method) In the spunbond method, a nonwoven fabric can be produced by supplying the resin composition used for the nonwoven fabric according to the embodiment described above to a spunbond nonwoven fabric production apparatus. The produced nonwoven fabric is collected on the collection surface of a conveyor, preferably a net conveyor, installed near the spunbond nonwoven fabric production apparatus. Note that such a conveyor may be part of the spunbond nonwoven fabric production apparatus.

[0101] An example of a manufacturing process in a spunbond nonwoven fabric manufacturing apparatus will be described. A resin composition containing a polyester resin (A) and a polylactic acid polymer (B) is supplied to the spunbond nonwoven fabric manufacturing apparatus, and is melt-kneaded at a temperature in the range of, for example, 200°C to 280°C to form a melt, which is then discharged through a number of nozzles (spinning holes). This makes the melt fibrous. The fibrous melt is subjected to a stretching process, thereby achieving further diameter reduction of the melt. During the stretching process, the melt is cooled as necessary. The diameter-reduced melt or its cooled counterpart is collected on the collecting surface of a conveyor as a nonwoven fabric. The collected nonwoven fabric may further undergo a process such as thermocompression bonding.

[0102] [Uses of Nonwoven Fabric] The uses of the nonwoven fabric according to the above-described embodiment and the nonwoven fabric obtained by the method for producing a nonwoven fabric according to the above-described embodiment are not particularly limited, and the nonwoven fabric can be effectively used for, for example, filters for food materials such as coffee filters and tea bag filters, various filters such as mask filters, air filters and liquid filters, various composite sheets (e.g., agricultural sheets, building material sheets, etc.) laminated and / or combined with other materials (e.g., nonwoven fabrics made only of polylactic acid, spunbonded nonwoven fabrics, spunlaced nonwoven fabrics, thermal-bonded nonwoven fabrics, etc.), pleated filters, work clothes, caps, etc.

[0103] The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these.

[0104] [Measurement and Evaluation Methods] Various physical properties were measured or evaluated by the following methods. The results are shown in Tables 1 and 2.

[0105] <Number Average Molecular Weight of Polyester Resin (A)> The polyester resins obtained in the Production Examples were used as samples, and the number average molecular weight (Mn) was determined by gel permeation chromatography (GPC) in terms of standard polystyrene. The specific measurement method is as follows.

[0106] (1) When Mn is less than 15,000, a tetrahydrofuran (THF) solution was used as the eluent, and 10 mg of the sample, calculated as resin, was weighed and dissolved in 1 mL of the eluent. The solution was passed through a 0.2 μm membrane filter to prepare a measurement sample. The specific measurement method is as follows. (Measurement conditions) Apparatus: HLC-EcoSEC8320GPC (manufactured by Tosoh Corporation) Column: Three columns, KF-803, KF-802.5, and KF-802 (manufactured by Showa Denko K.K.), were connected in series. Eluent: tetrahydrofuran Flow rate: 0.9 mL / min Sample injection amount: 30 μL Column temperature: 40°C Standard polystyrene: PSt Oligomer Kit (molecular weight 589 to 98,900) manufactured by Tosoh Corporation was used, and cubic approximation was performed. Detector: RI detector

[0107] (2) When Mn was 15,000 or more, a tetrahydrofuran (THF) solution was used as the eluent. 1.0 mg of the sample was weighed in terms of resin and dissolved in 1 mL of the above eluent. The solution was passed through a 0.2 μm membrane filter to prepare a measurement sample. The measurement conditions were as follows. (Measurement conditions) Apparatus: HLC-8220GPC (manufactured by Tosoh Corporation) Column: Two TSK-gel SuperMultipore HZ-M (manufactured by Tosoh Corporation) connected in series. Eluent: tetrahydrofuran Flow rate: 0.35 mL / min Sample injection amount: 10 μL Column temperature: 40°C Standard polystyrene: Polystyrene molecular weight standard (molecular weight 580 to 1,214,000) manufactured by GL Sciences Inc. was used for cubic approximation. Detector: RI detector

[0108] <Ratio (molar ratio) of each component of polyester-based resin> The polyester-based resin obtained in the production example was used as a sample, and the ratio (molar ratio) of each component of the polyester-based resin was calculated as follows: １The molar ratio was determined by H-NMR measurement. The measurement conditions were as follows. The molar ratio was calculated from the area ratio of the signals derived from each component in the obtained spectrum. (Measurement conditions) Apparatus: 400YH (manufactured by JEOL Ltd.) Solvent: deuterated chloroform (CDCl ３ ) Measurement temperature: 23°C Number of accumulations: 32 (Signals) For aliphatic diols, the signal was the proton bonded to the carbon at the β-position of the OH group, and for polycarboxylic acids, the signal was the proton bonded to the carbon to which the carbonyl group is bonded. Note that in aliphatic diols, if no proton is bonded to the carbon at the β-position of the OH group, the signal was the proton bonded to the carbon to which the OH group is bonded, and in polycarboxylic acids, if no proton is bonded to the carbon to which the carbonyl group is bonded, the signal was the proton bonded to the carbon to which the β-position is bonded. Note that the signals of the aliphatic diols and polycarboxylic acids used in the production examples are as follows: 3-methyl-1,5-pentanediol: 4.0-4.2 ppm Adipic acid: 2.2-2.4 ppm

[0109] <Measurement of Melt Mass Flow Rate (MFR) of Resin> The MFR of the resin composition and the polylactic acid polymer (B) was measured in accordance with JIS K 7210-1: 2014 using a commercially available measuring device (Melt Indexer G-02, manufactured by Toyo Seiki Seisaku-sho, Ltd.) Note that the catalog value was used for the MFR of the polyolefin resin (D-1).

[0110] <Evaluation of Productivity> The nonwoven fabrics obtained in the examples and comparative examples were visually inspected for the occurrence of shots (polymer lumps) and fly dust, and the number of shots per unit area and the mass of fly dust per unit time were measured.

[0111] The observation results were evaluated based on the following criteria: "A": 0.1 shots / m ２ "B": Both shots and fly occurred, with the number of shots being 0.1 / m or less. ２ 1 piece / m or more ２At least one of the following requirements was met: and the requirement that the fly was 10 mg / min or more and 100 mg / min or less. "C": Both shots and fly were generated, with the number of shots being 1 / m. ２ At least one of the requirements of more than 100 mg / min and the requirement of more than 100 mg / min of fly dust was satisfied. Even if one of the shots and fly dust satisfied the requirement of criterion "B" above, if the other satisfied the requirement of criterion "C," the evaluation result was rated "C." It is known that shots and fly dust can occur when spinning stability is poor during nonwoven fabric production. Therefore, in this example, the number of shots generated per unit area and the mass of fly dust generated per unit time were used as evaluation criteria for yield (productivity).

[0112] <Basis Weight of Nonwoven Fabric> Square test pieces with sides of 20 cm were taken from the nonwoven fabrics obtained in the Examples and Comparative Examples. When taking the test pieces, two opposing sides of the square were aligned with the conveyor movement direction (MD direction) during nonwoven fabric production. Next, for each test piece, three locations were selected along the width direction of the test piece (direction perpendicular to the conveyor movement direction: TD direction), and the basis weight was measured in accordance with JIS L 1096:2020. The average value of these measurements was then taken as the basis weight of the nonwoven fabric.

[0113] <Thickness of Nonwoven Fabric> Square measurement samples with sides of 20 cm were taken from the nonwoven fabrics obtained in the Examples and Comparative Examples. Each measurement sample was left to stand under a standard environment (temperature: 20°C, relative humidity: 65%) for 4 hours or more to obtain a measurement sample. Thereafter, the thickness was measured using a thickness measuring instrument "Digital Thickness Meter No. 132" (measuring probe: φ16 mm, load: 20 gf / cm) manufactured by Toyo Seiki Seisakusho Co., Ltd. ２ The thickness (mm) of the nonwoven fabric was measured at five points, namely, the center and four corners of the sample. The average of these measurements was taken as the thickness (mm) of the nonwoven fabric.

[0114] <Air Permeability of Nonwoven Fabric> The air permeability of the nonwoven fabrics obtained in the examples and comparative examples was measured in accordance with the Frazier test method of JIS L 1913:2010 "General Testing Methods for Nonwoven Fabrics." A commercially available Frazier tester ("FX3300" manufactured by TEXTEST Co., Ltd.) was used, and the measurement area was 38 cm.２ The measurement was carried out under the condition of a measurement pressure of 125 Pa.

[0115] <Crystallization exothermic peak temperature of nonwoven fabric> Using a differential scanning calorimeter (TA Instrument "DSC25"), the nonwoven fabrics obtained in the examples and comparative examples were heated from 30°C to 220°C at a rate of 10°C / min under a nitrogen flow rate (100 mL / min), held at 220°C for 5 minutes, and then cooled to -90°C at a rate of 10°C / min. After holding at -90°C for 5 minutes, the fabric was heated to 220°C at a rate of 10°C / min to obtain a DSC curve. The crystallization peak temperature determined from the DSC curve and described in JIS K7121:2012 was taken as the crystallization exothermic peak temperature Tc (°C).

[0116] <Evaluation of Low Heat Shrinkage: Measurement of Dry Heat Shrinkage of Nonwoven Fabric> Test pieces measuring 20 cm wide x 20 cm long were cut out from the nonwoven fabrics obtained in the Examples and Comparative Examples. When cutting out the test pieces, one pair of opposing sides was aligned with the direction of conveyor movement (MD) during nonwoven fabric production. Next, the TD dimension A0 and MD dimension B0 of each test piece were measured.

[0117] Thereafter, each test piece was placed in a thermostatic oven at 100°C and left there for 1 minute to be heated, and then removed from the oven and cooled to room temperature. Next, the TD dimension A1 and MD dimension B1 of the test piece after being removed from the oven were measured.

[0118] The dry heat shrinkage percentage ΔA(TD) (%) in the TD direction and the dry heat shrinkage percentage ΔA(MD) (%) in the MD direction of the nonwoven fabric were then calculated using the following formulas: ΔA(TD)={(A0-A1) / A0}×100 (In the above formula, A0 is the TD dimension (cm) of the test piece before it was placed in the oven, and A1 is the TD dimension (cm) of the test piece after it was removed from the oven.) ΔA(MD)={(B0-B1) / B0}×100 (In the above formula, B0 is the MD dimension (cm) of the test piece before it was placed in the oven, and B1 is the MD dimension (cm) of the test piece after it was removed from the oven.)

[0119] <Evaluation of extensibility of nonwoven fabrics: measurement of elongation percentage> Five first test pieces (50 mm wide, 20 cm long test pieces) along the warp direction of the nonwoven fabric and five second test pieces (50 mm wide, 20 cm long test pieces) along the weft direction of the nonwoven fabric were taken from the nonwoven fabrics obtained in the Examples and Comparative Examples according to JIS L 1913:2010 "Testing methods for general nonwoven fabrics." Here, the warp direction was the direction of movement of the conveyor during nonwoven fabric production (MD direction), and the weft direction was the direction perpendicular to the MD direction (TD direction).

[0120] Next, for the first test piece and the second test piece, the standard elongation was measured using an "Autograph" manufactured by Shimadzu Corporation in accordance with JIS L 1913:2010 "Testing methods for general nonwoven fabrics" at a grip distance of 100 mm and a pulling speed of 300 mm / min. The average value of the measured values ​​for the first test piece was taken as the elongation in the machine direction ΔE (MD) (%), and the average value of the measured values ​​for the second test piece was taken as the elongation in the width direction ΔE (TD) (%).

[0121] <Qualitative Evaluation of Biodegradability> The biodegradability of the nonwoven fabrics obtained in the Examples and Comparative Examples was evaluated using the nonwoven fabric of Comparative Example 1 as the standard, according to the following evaluation criteria. "A": From the resin composition used, biodegradability equivalent to that of the nonwoven fabric of Comparative Example 1 was expected. "B": From the resin composition used, biodegradability sufficient for practical use, although not equivalent to that of the nonwoven fabric of Comparative Example 1, was expected. "C": From the resin composition used, biodegradability insufficient for practical use was expected. Note that when the content of the less biodegradable component in the resin composition is relatively high compared to that of Comparative Example 1, it is considered that the resin composition is expected to have poor biodegradability, while when the content of the less biodegradable component in the resin composition is relatively low compared to that of Comparative Example 1, it is considered that the resin composition is expected to have excellent biodegradability.

[0122] [Materials] The materials used in the examples and comparative examples are as follows.

[0123] (Polyester Resin (A)) Polyester Resin (A-1): Polyester diol obtained in Production Example 1 below [Production Example 1] 3-methyl-1,5-pentanediol and adipic acid were charged into a flask equipped with a vacuum pump and an apparatus capable of distilling off the generated liquid, in a molar ratio of 3-methyl-1,5-pentanediol / adipic acid = 1.12 / 1. The mixture was heated under a nitrogen atmosphere at normal pressure at 160°C for 3 hours, and then at 220°C for 3 hours, to carry out a reaction while distilling off volatile components such as water. Next, 150 μL of tetraisopropyl titanate was added, and the pressure was reduced to 2,000 Pa to carry out a reaction for 3 hours. After that, the pressure was further reduced to 80 Pa and the reaction was continued while checking as necessary until the number average molecular weight reached 3,000. During the reaction, the volatile components were continuously distilled off, and the cyclic ester compound (C) was discharged from the system. This resulted in a polyester diol as polyester resin (A-1).

[0124]

[0125] (Polylactic acid polymer (B)) Polylactic acid polymer (B-1): "Luminy L105" manufactured by Total Energy Corbion (D-lactic acid:L-lactic acid = 1:99 (molar ratio), MFR (190°C, 2.16 kg): 30 g / 10 min)

[0126] (Cyclic Ester Compound (C)) Cyclic Ester Compound (C-1): 4-methyl-1,7-dioxacyclotridecane-8,13-dione

[0127] [Production Example 2] A separatory funnel was charged with the distillate obtained in Production Example 1, toluene, and water in a mass ratio of distillate / toluene / water = 1 / 10 / 10, and 4-methyl-1,7-dioxacyclotridecane-8,13-dione contained in the distillate was extracted into toluene. The toluene layer was added to an eggplant flask and air-dried overnight at 20°C to volatilize the toluene, and then dried in a vacuum dryer at 20°C and 100 Pa for 1 hour to obtain crystals of 4-methyl-1,7-dioxacyclotridecane-8,13-dione (cyclic ester compound (C-1)), a cyclic ester compound.

[0128] (Other Components (D)) Polyolefin Resin (D-1): "S13B" manufactured by Prime Polymer Co., Ltd. (MFR (230°C, 2.16 kg): 300 g / 10 min)

[0129] [Example 1] (Preparation of resin composition) The polyester resin (A-1) and polylactic acid polymer (B-1) obtained in the production example were charged into a twin-screw kneader ("ULTnano 50" manufactured by Technovel Co., Ltd.) in the formulation shown in Table 2, and extruded into strands at a cylinder temperature of 200 ° C., a screw rotation speed of 50 rpm, and a residence time of 1 minute. The resulting strands were cut into pellets to obtain a resin composition. The MFR (190 ° C., 2.16 kg) of the resulting resin composition was measured in accordance with JIS K 7210-1:2014 using a commercially available measuring device, and was found to be 60 g / 10 min.

[0130] (Production of nonwoven fabric) The obtained resin composition was dried at 80 ° C. for 5 hours. The dried resin composition was supplied to a general meltblown nonwoven fabric production apparatus, and a nonwoven fabric was produced by the meltblown method as follows. This nonwoven fabric production apparatus was an apparatus including an extruder, a die formed with a nozzle (spinning hole), and a blower formed with a slit. The nozzle of the die had a nozzle single hole diameter D (diameter) of 0.30 mm, a nozzle single hole length L / nozzle single hole diameter D of 10, a nozzle hole pitch of 0.75 mm, and the number of spinning holes was 1300 holes / m (single row arrangement). The slit of the blower was provided in the vicinity of the spinning hole.

[0131] Specifically, the supplied resin composition was first melted in an extruder set at 220°C, then fed into a die set at 280°C, and extruded from the nozzle of the die at a single-hole discharge rate of 0.3 g / min / h. At the same time, the resin composition was blown out from the slit of the blower at a temperature of 280°C and a flow rate of 15.7 Nm per 1 m width. ３Hot air was blown out at a rate of 1 / min. This reduced the diameter of the discharged fibers. The reduced-diameter fibers were then collected on the collection surface of a net conveyor. This net conveyor was positioned so that its collection surface was horizontal and 15 cm vertically below the bottom surface of the die nozzle. The net conveyor operated at a speed of 17.6 m / min in the MD direction during nonwoven fabric production. In this way, the nonwoven fabric of Example 1 was produced. The size of the nonwoven fabric was 30 cm wide and 30 m long.

[0132] (Measurement and Evaluation of Nonwoven Fabric) The nonwoven fabric obtained was subjected to the above-described measurement and evaluation. The results are shown in Table 2.

[0133] [Example 2] A resin composition was obtained in the same manner as in Example 1, except that the formulation was changed as shown in Table 2. The MFR (190°C, 2.16 kg) of the obtained resin composition was measured in the same manner as above and was found to be 80 g / 10 min. When a nonwoven fabric was produced from the obtained resin composition, the volume of hot air blown out of the slit was 13.7 Nm per 1 m width. ３ A nonwoven fabric according to Example 2 was produced in the same manner as in Example 1, except that the speed was changed to / min. The nonwoven fabric obtained was subjected to measurements and evaluations in the same manner as in Example 1. The results are shown in Table 2.

[0134] [Example 3] A resin composition was obtained in the same manner as in Example 1, except that the formulation was changed as shown in Table 2. The MFR (190°C, 2.16 kg) of the obtained resin composition was measured in the same manner as above and was found to be 120 g / 10 min. When a nonwoven fabric was produced from the obtained resin composition, the volume of hot air blown out of the slit was 12.6 Nm per 1 m width. ３ A nonwoven fabric according to Example 3 was produced in the same manner as in Example 1, except that the speed was changed to / min. The nonwoven fabric obtained was subjected to measurements and evaluations in the same manner as in Example 1. The results are shown in Table 2.

[0135] [Example 4] A resin composition was obtained in the same manner as in Example 1, except that the formulation was changed as shown in Table 2. The MFR (190°C, 2.16 kg) of the obtained resin composition was measured in the same manner as above and was found to be 180 g / 10 min. In producing a nonwoven fabric from the obtained resin composition, the die temperature and the hot air temperature of the air blower were set to 260°C, and the volume of hot air blown from the slit was 14.8 Nm per meter width. ３ A nonwoven fabric according to Example 4 was produced in the same manner as in Example 1, except that the flow rate was changed to / min. The nonwoven fabric thus obtained was subjected to measurements and evaluations in the same manner as in Example 1. The results are shown in Table 2.

[0136] [Example 5] A resin composition was obtained in the same manner as in Example 1, except for changing the formulation as shown in Table 2. The MFR (190°C, 2.16 kg) of the obtained resin composition was measured in the same manner as above, and was found to be above the upper limit of measurement, estimated to be 200 g / 10 min or more. In producing a nonwoven fabric from the obtained resin composition, the extruder temperature was set to 210°C, the die temperature and the hot air temperature of the air blower were set to 255°C, and the volume of hot air blown from the slit was set to 16.8 Nm per meter width. ３ A nonwoven fabric according to Example 5 was produced in the same manner as in Example 1, except that the speed was changed to / min. The nonwoven fabric obtained was subjected to measurements and evaluations in the same manner as in Example 1. The results are shown in Table 2.

[0137] [Example 6] A resin composition was obtained in the same manner as in Example 1, except that the formulation was changed as shown in Table 2. The MFR (190°C, 2.16 kg) of the obtained resin composition was measured in the same manner as above and was found to be 80 g / 10 min. When a nonwoven fabric was produced from the obtained resin composition, the volume of hot air blown out of the slit was 13.7 Nm per 1 m width. ３ A nonwoven fabric according to Example 6 was produced in the same manner as in Example 1, except that the speed was changed to / min. The nonwoven fabric obtained was subjected to measurements and evaluations in the same manner as in Example 1. The results are shown in Table 2.

[0138] [Example 7] A resin composition was obtained in the same manner as in Example 1, except that the formulation was changed as shown in Table 2. The MFR (190°C, 2.16 kg) of the obtained resin composition was measured in the same manner as above and was found to be 80 g / 10 min. When a nonwoven fabric was produced from the obtained resin composition, the volume of hot air blown out of the slit was 13.7 Nm per 1 m width. ３ A nonwoven fabric according to Example 7 was produced in the same manner as in Example 1, except that the flow rate was changed to / min. The nonwoven fabric obtained was subjected to measurements and evaluations in the same manner as in Example 1. The results are shown in Table 2.

[0139] [Comparative Example 1] Instead of the resin composition of Example 1, polylactic acid polymer (B-1) was used alone. That is, in Comparative Example 1, polyester resin (A-1) and other components (D-1) were not used. When producing a nonwoven fabric from polylactic acid polymer (B-1), the volume of hot air blown out of the slit was 16.8 Nm per meter width. ３ A nonwoven fabric according to Comparative Example 1 was produced in the same manner as in Example 1, except that the flow rate was changed to / min. The nonwoven fabric obtained was subjected to measurements and evaluations in the same manner as in Example 1. The results are shown in Table 2.

[0140] Comparative Example 2 A resin composition was obtained in the same manner as in Example 5, except for the formulation shown in Table 2. That is, in Comparative Example 2, 25 parts by mass of a polyolefin resin was used as the other component (D-1) instead of 25 parts by mass of the polyester resin (A-1). The MFR (230°C, 2.16 kg) of the obtained resin composition was measured in the same manner as above and found to be 65 g / 10 min. A nonwoven fabric according to Comparative Example 2 was produced from the obtained resin composition in the same manner as in Example 5. The obtained nonwoven fabric was then subjected to measurements and evaluations in the same manner as in Example 5. The results are shown in Table 2. The obtained nonwoven fabric contained scattered shot and fly lint and had a poor yield for practical use, suggesting that the spinning stability during production was not as excellent as that of Example 5.

[0141] [Comparative Example 3] When a nonwoven fabric was produced in the same manner as in Example 1 using the resin composition obtained in Comparative Example 1, the volume of hot air blown out of the slit was 18.8 Nm per meter width. ３When the spinning speed was changed to / min, a large amount of fly fluff was generated per unit area. Since the spinning stability during production was not excellent and the yield was also not excellent, the nonwoven fabric of Comparative Example 3 was not subjected to measurement and evaluation.

[0142]

[0143] A comparison between the Examples and Comparative Example 1 revealed that the nonwoven fabrics according to the Examples had excellent low heat shrinkage and excellent extensibility. Furthermore, it was found that the nonwoven fabrics according to the Examples were comparable to the nonwoven fabric according to Comparative Example 2 in terms of heat shrinkage, and superior to the nonwoven fabric according to Comparative Example 2 in terms of extensibility. A comparison between Comparative Examples 1 and 2 revealed that the polyolefin resin had no effect of improving the extensibility of the polylactic acid polymer, and therefore the excellent extensibility of the nonwoven fabrics according to the Examples was an unexpected effect.

[0144] Furthermore, by comparing the Examples with the Comparative Examples, it was found that the nonwoven fabrics according to the Examples had excellent yield and productivity. Therefore, it was found that the Examples can provide a method for manufacturing a nonwoven fabric with excellent productivity.

[0145] Furthermore, it was found that the nonwoven fabric of Example 5 was significantly superior in terms of breathability to the nonwoven fabric of Comparative Example 2, despite employing the same manufacturing conditions as the nonwoven fabric of Comparative Example 2. Therefore, it was found that the resin composition used in the examples allows for the reduction of fiber diameters when producing nonwoven fabrics.

[0146] Furthermore, since polyester-based resins are generally more biodegradable than polyolefin-based resins, it was expected that the nonwoven fabrics according to the examples would be more biodegradable than the nonwoven fabric according to Comparative Example 2.

Claims

1. A nonwoven fabric comprising fibers formed from a resin composition containing a polyester resin (A) and a polylactic acid polymer (B), wherein the polyester resin (A) contains units derived from a polyhydric alcohol (a1) and units derived from a polycarboxylic acid (a2), and the polyhydric alcohol (a1) contains an aliphatic diol (a1-1) having 4 or more carbon atoms and having an alkyl group as a branched chain.

2. The nonwoven fabric according to claim 1, wherein the polycarboxylic acid (a2) is an aliphatic dicarboxylic acid (a2-1).

3. The nonwoven fabric according to claim 2, wherein the aliphatic dicarboxylic acid (a2-1) is at least one selected from the group consisting of adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.

4. The nonwoven fabric according to claim 1, wherein the number average molecular weight of the polyester resin (A) is 500 to 100,000.

5. The nonwoven fabric according to claim 1, which contains 0.1 to 50 parts by mass of the polyester resin (A) per 100 parts by mass of the polylactic acid polymer (B).

6. The nonwoven fabric according to claim 1, wherein the polycarboxylic acid (a2) is an aliphatic dicarboxylic acid (a2-1), the aliphatic dicarboxylic acid (a2-1) includes adipic acid, and the number average molecular weight of the polyester resin (A) is 500 to 100,000.

7. The nonwoven fabric according to claim 1, wherein the polycarboxylic acid (a2) is an aliphatic dicarboxylic acid (a2-1), the aliphatic dicarboxylic acid (a2-1) includes sebacic acid, and the number average molecular weight of the polyester resin (A) is 500 to 100,000.

8. The nonwoven fabric according to claim 1, which contains 0.001 to 3.0 parts by mass of a cyclic ester compound (C) per 100 parts by mass of the polylactic acid polymer (B).

9. The nonwoven fabric according to claim 1, wherein the polyester resin (A) is a polyester diol.

10. The nonwoven fabric according to claim 1, wherein the melt mass flow rate (MFR) of the resin composition measured under conditions of a temperature of 190°C and a load of 2.16 kg is 40 g / 10 min or more and 300 g / 10 min or less.

11. A method for producing a nonwoven fabric according to any one of claims 1 to 10, comprising the steps of melt-kneading a resin composition containing a polyester resin (A) and a polylactic acid polymer (B) to obtain a molten material, and subjecting the molten material to a melt-blown method or a spunbond method to obtain a nonwoven fabric.

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