Hot-melt adhesive composite fiber, nonwoven fabric, and absorbent article

Abstract

Provided are a heat-fusible composite fiber, a nonwoven fabric, and an absorbent article, which suppress consumption of fossil resources and impart both bulkiness and softness to a nonwoven fabric. A heat-fusible composite fiber is a heat-fusible composite fiber in which a first component contains a polyester-based resin and a second component contains a polyethylene-based resin having a lower melting point than the first component, and in the polyethylene-based resin, the blending ratio (weight ratio) of a biomass-derived polyethylene-based resin to a fossil resource-derived polyethylene-based resin is 20:80 to 90:10.

Description

Technical Field

[0001] This invention relates to a heat-fused composite fiber containing components derived from biomass and nonwoven fabrics and absorbent articles obtained therefrom. Background Technology

[0002] Previously, nonwoven fabrics with excellent bulk and softness could be easily obtained by using the heat energy of hot air or heated rollers to form heat-fused composite fibers. Therefore, they were widely used in hygiene materials such as diapers, sanitary napkins, and panty liners, as well as industrial materials such as household goods and filters. Especially since hygiene materials come into direct contact with human skin or need to quickly absorb liquids such as urine and menstrual blood, bulk and softness are extremely important. To achieve bulk, a representative method is to use high-rigidity resins or to achieve rigidity through high-ratio stretching; however, in these cases, the softness of the resulting nonwoven fabric decreases. On the other hand, if softness is prioritized, the bulk of the resulting nonwoven fabric decreases, and its liquid absorbency deteriorates.

[0003] Therefore, a method for obtaining fibers and nonwoven fabrics that possess both fluffiness and softness has been proposed. Patent Document 1 discloses a heat-welding composite fiber in which the first component is a polyester resin and the second component is a polyolefin resin with a melting point lower than that of the first component, and describes how a fluffi and soft nonwoven fabric can be obtained by using the fiber.

[0004] Furthermore, in recent years, with the growing calls for building a circular society, there is a desire in the materials field to break free from fossil resources, just as with energy, and the utilization of biomass-derived materials has received considerable attention. Biomass is an organic compound synthesized from carbon dioxide and water through photosynthesis (see, for example, Patent Documents 2 and 3). If materials derived from such biomass are effectively used as starting materials, the consumption of fossil resources can be reduced. For example, if biomass-derived materials such as polylactic acid are used as raw materials, even if they are incinerated after use and decomposed into carbon dioxide and water, they are still equivalent to the amount of carbon dioxide and water that entered the plant through photosynthesis, thus enabling the construction of a recycling system or carbon neutrality.

[0005] Against this backdrop, composite fibers made from biomass-derived materials have also been proposed in the field of sanitary materials. Patent document 4 discloses a polyethylene terephthalate (PET) and polyethylene (PE) composite fiber made from biomass-derived materials, describing how a nonwoven fabric with a uniform texture can be obtained by suppressing the consumption of fossil resources and polymerizing various polymers with PE.

[0006] Generally speaking, biomass-derived resins do not differ chemically from those derived from fossil resources, and therefore are considered to have no difference in quality. However, biomass-derived resins contain impurities in their raw material monomers that cannot be removed during manufacturing, resulting in decreased heat resistance and other issues. Therefore, they cannot be used in the same way as fossil-derived resins. Particularly in the manufacture of nonwoven fabrics for hygiene materials, methods such as fiber fineness reduction can be used to obtain good softness or hand feel. However, when using conventional biomass-derived resins, it is difficult to obtain fine-fine heat-fused composite fibers. Furthermore, even if fine-fine heat-fused composite fibers are obtained, the nonwoven fabrics made from these fibers have very low bulk.

[0007] [Existing Technical Documents]

[0008] [Patent Literature]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2017-214662

[0010] [Patent Document 2] Japanese Patent Application Publication No. 2009-091694

[0011] [Patent Document 3] Japanese Patent Application Publication No. 2008-150759

[0012] [Patent Document 4] Japanese Patent Application Publication No. 2012-140728 Summary of the Invention

[0013] [The problem the invention aims to solve]

[0014] Thus, in the prior art, if one wants to obtain a nonwoven fabric that has both the required level of fluffiness and softness for use as a sanitary material, it is necessary to use materials that contain only fossil resources, without obtaining a nonwoven fabric that has both fluffiness and softness while suppressing the consumption of fossil resources.

[0015] The present invention was made in the context of the prior art, and its purpose is to provide a heat-fused composite fiber that inhibits the consumption of fossil resources and imparts both bulkiness and softness to nonwoven fabrics, and a nonwoven fabric using the same.

[0016] [Technical means to solve the problem]

[0017] The inventors have conducted repeated research to solve the aforementioned problem. As a result, it was discovered that the problem can be solved by blending a biomass-derived polyethylene resin and a fossil-derived polyethylene resin in an appropriate ratio as the polyethylene resin in a heat-melting composite fiber in which the first component comprises a polyester resin and the second component comprises a polyethylene resin with a melting point lower than that of the first component. This led to the completion of the present invention.

[0018] That is, the present invention is configured in the following manner.

[0019] [1] A thermo-meltable composite fiber is a thermo-meltable composite fiber in which the first component comprises a polyester resin and the second component comprises a polyethylene resin with a melting point lower than that of the first component, wherein the polyethylene resin derived from biomass and the polyethylene resin derived from fossil resources are mixed in a ratio (by weight) of 20:80 to 90:10.

[0020] [2] According to the heat-melting composite fiber of [1], the carbon content of the biomass-derived polyethylene resin is 20% to 90%.

[0021] [3] The heat-fusion composite fiber according to [1] or [2], wherein the biomass-derived carbon content in the heat-fusion composite fiber is more than 10%.

[0022] [4] The heat-melting composite fiber according to any one of [1] to [3], wherein the carbon content of the biomass-derived polyester resin is less than 30%.

[0023] [5] The heat-fusion composite fiber according to any one of [1] to [4], wherein the fineness of the heat-fusion composite fiber is 2.2 dtex or less.

[0024] [6] The heat-fusion composite fiber according to any one of [1] to [5], wherein the heat of fusion of the polyester resin in the heat-fusion composite fiber is 24 J / g or more.

[0025] [7] The heat-fusion composite fiber according to any one of [1] to [6], wherein the heat-fusion composite fiber is a sheath-core type heat-fusion composite fiber with the first component as the core component and the second component as the sheath component.

[0026] [8] The heat-melting composite fiber according to any one of [1] to [7], wherein the polyester resin is polyethylene terephthalate and the polyethylene resin is high-density polyethylene.

[0027] [9] A nonwoven fabric comprising thermally bondable composite fibers according to any one of [1] to [8].

[0028]

[10] An absorbent article using a heat-fused composite fiber according to any one of [1] to [8].

[0029] [The effects of the invention]

[0030] According to the present invention, a heat-fused composite fiber can be provided that inhibits the consumption of fossil resources and imparts both bulkiness and softness to nonwoven fabrics. Detailed Implementation

[0031] The thermally bondable composite fiber of the present invention is characterized in that: the first component contains a polyester resin, the second component contains a polyethylene resin with a melting point lower than that of the first component, and the polyethylene resin is mixed in a ratio (by weight) of polyethylene resin derived from biomass to polyethylene resin derived from fossil resources of 20:80 to 90:10.

[0032] (First component)

[0033] The polyester resin constituting the first component of this invention is not particularly limited, but aromatic polyester resins such as polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate are preferably used. In addition to the aromatic polyester resins mentioned above, aliphatic polyester resins can also be used; examples of preferred aliphatic polyester resins include polylactic acid or polybutylene succinate. These polyester resins can be homopolymers or copolyesters. In this case, as the copolymerizing component, dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, diol components such as diethylene glycol and neopentyl glycol, and optical isomers such as L-lactic acid can be used. Examples of such copolymers include polybutylene terephthalate adipate. Furthermore, two or more of these polyester resins can be mixed and used. Among these considerations, taking into account raw material costs, the bulkiness of the nonwoven fabric, and the thermal stability of the obtained fibers, the preferred first component is an unmodified polymer containing only polyethylene terephthalate.

[0034] When the polyester resin is an aromatic polyester resin, it can be obtained, for example, by polycondensation of a diol and a dicarboxylic acid. Examples of dicarboxylic acids used in the polycondensation of polyester resins include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, and sebacic acid. Examples of diols used include ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanediethanol.

[0035] The carbon content of the biomass-derived material in the polyester resin of this invention is not particularly limited, but is preferably 30% or less, more preferably 2% to 28%, and even more preferably 6% to 24%. If the carbon content of the biomass-derived material in the polyester resin is 2% or more, the consumption of fossil resources can be reduced, so it is preferred. If it is 30% or less, it is easier to maintain the original physical properties of the polyester resin, and the nonwoven fabric can have fluffiness and softness, so it is preferred.

[0036] Here, the carbon content derived from biomass refers to the carbon content obtained through radioactive carbon (RTC). 14 C) The value is obtained by measuring the carbon content derived from biomass. It is known that atmospheric carbon dioxide contains a certain proportion (10⁷ pMC, percentage of modern carbon) of... 14 C, therefore, plants that grow by absorbing carbon dioxide from the atmosphere, such as corn 14 The carbon content is also around 107 pMC. Additionally, 14 Carbon (C) reverts to nitrogen atoms in its half-life of 5,370 years, and complete decay takes 226,000 years. Therefore, carbon dioxide and other atmospheric pollutants, once absorbed and fixed by plants and other organisms, are considered to be almost entirely absent in fossil fuels such as coal, oil, and natural gas after more than 226,000 years. 14 C. Therefore, by determining the total carbon atoms contained in the resin... 14 The proportion of C allows for the calculation of the carbon content derived from biomass. The method for calculating the carbon content derived from biomass in the resin of this invention is described in detail in the embodiments described later.

[0037] The polyester resin is not particularly limited, but in terms of suppressing the consumption of fossil resources without impairing the original physical properties of the polyester resin and giving the nonwoven fabric a fluffy and soft feel, it is preferable to include a polyester resin derived from biomass and a polyester resin derived from fossil resources. From this perspective, the mixing ratio (by weight) of the polyester resin derived from biomass to the polyester resin derived from fossil resources is not particularly limited, but is preferably 5:95 to 95:5, more preferably 20:80 to 80:20.

[0038] Here, the term "biomass-derived polyester resin" simply refers to a polyester resin that contains carbon derived from biomass, preferably with a biomass-derived carbon content of 10% or more, more preferably 20% or more. This biomass-derived polyester resin can be a polymer containing only biomass-derived monomers, or a copolymer of biomass-derived monomers and fossil-derived monomers. Examples include copolymers of biomass-derived diols and biomass-derived dicarboxylic acids, copolymers of biomass-derived diols and fossil-derived dicarboxylic acids, and copolymers of fossil-derived diols and biomass-derived dicarboxylic acids. From the viewpoint of easy availability, copolymers of biomass-derived diols and fossil-derived dicarboxylic acids are preferred.

[0039] There are no particular limitations on the biomass-derived polyester resin. Resins obtained by existing known methods can be used, as well as commercially available biomass-derived polyethylene terephthalate from companies such as Far East Textile Corporation, or commercially available biomass-derived polylactic acid from companies such as NatureWorks.

[0040] Furthermore, so-called fossil-derived polyester resins refer to polyester resins that do not contain carbon derived from biomass, that is, polyester resins with a biomass-derived carbon content of 0%. Therefore, as fossil-derived polyester resins, they are resins polymerized solely from monomers derived from fossil resources.

[0041] If the first component contains polyester resin, there are no particular limitations, but it is preferable to contain 80% or more by mass of polyester resin, and more preferably 90% or more by mass of polyester resin. Within the scope that does not impair the effects of the present invention, antioxidants, light stabilizers, ultraviolet absorbers, neutralizing agents, nucleating agents, epoxy stabilizers, lubricants, antibacterial agents, flame retardants, antistatic agents, pigments, or plasticizers may be added as needed.

[0042] (Second component)

[0043] The polyethylene resin used in this invention is not particularly limited, and examples include high-density polyethylene, linear low-density polyethylene, low-density polyethylene, or copolymers of ethylene with other components (e.g., α-olefins), or mixtures thereof. From the viewpoint of suppressing the phenomenon that the polyethylene resin exposed on the fiber surface does not completely cool and solidify and fuse with each other during spinning, it is preferable to contain only high-density polyethylene.

[0044] Importantly, the blending ratio (by weight) of the biomass-derived polyethylene resin and the fossil-derived polyethylene resin constituting the second component of this invention is 20:80 to 90:10. As with existing technologies, it is believed that when using only biomass-derived polyethylene resin, if the resin is subjected to a thermal process approaching 300°C during melting, the resin's viscosity or molecular weight will decrease, resulting in insufficient extensibility and difficulty in achieving both fineness and rigidity in the composite fiber, thus failing to obtain a soft and fluffy nonwoven fabric. This invention has discovered that by setting the blending ratio of biomass-derived polyethylene resin to 90% by weight or less, the decrease in viscosity or molecular weight of the polyethylene resin is suppressed; by maintaining a moderate elongation rate during the composite fiber formation process, both fineness and rigidity of the composite fiber can be achieved; furthermore, by setting the blending ratio of biomass-derived polyethylene resin to 20% by weight or more, not only can the carbon content of the biomass-derived composite fiber be increased and the consumption of fossil resources be suppressed, but the softness of the nonwoven fabric can also be further improved. In view of the above, the mixing ratio (by weight) of polyethylene resin derived from biomass and polyethylene resin derived from fossil resources is preferably 30:70 to 70:30, more preferably 40:60 to 50:50.

[0045] Here, the term "biomass-derived polyethylene resin" simply refers to a polymer containing carbon derived from biomass, preferably with a biomass-derived carbon content of 90% or more, more preferably 94% or more. This biomass-derived polyethylene resin can be a polymer containing only biomass-derived monomers, or a polymer of biomass-derived monomers and monomers derived from fossil resources. Examples include polymers of ethylene derived from biomass, copolymers of ethylene derived from biomass and α-olefins (propylene, butene, hexene, octene, etc.) derived from biomass, copolymers of ethylene derived from biomass and ethylene derived from fossil resources, copolymers of ethylene derived from biomass and α-olefins derived from fossil resources, or copolymers of α-olefins derived from biomass and ethylene derived from fossil resources. From the viewpoint of suppressing fiber adhesion during composite fiber forming, a biomass-derived polyethylene resin is preferably a polymer of ethylene derived from biomass or a polymer of ethylene derived from biomass and ethylene derived from fossil resources.

[0046] There are no particular limitations on the biomass-derived polyethylene resins. Resins obtained by existing known methods can be used, for example, by using microorganisms to ferment starch or sugar obtained from corn, sugarcane, sweet potatoes, etc., to produce bioethanol, followed by a dehydration reaction to produce biomass-derived ethylene, which is then polymerized. Alternatively, commercially available biomass-derived polyethylene resins from companies such as Braskem can also be used.

[0047] Furthermore, the term "fossil-derived polyethylene resin" refers to a polyethylene resin that contains no carbon derived from biomass, i.e., has a biomass-derived carbon content of 0%. Therefore, as a fossil-derived polyethylene resin, it is polymerized solely from monomers derived from fossil resources, such as polymers of ethylene derived from fossil resources, and copolymers of ethylene derived from fossil resources and α-olefins derived from fossil resources. From the viewpoint of suppressing fiber adhesion during composite fiber forming, polymers of ethylene derived from fossil resources are preferred as the fossil-derived polyethylene resin.

[0048] The density of polyethylene resins derived from biomass is not particularly limited, but 0.91 g / cm³ is an example. 3 ~0.96g / cm 3 Furthermore, the density of polyethylene-based resins derived from fossil resources is not particularly limited, but 0.91 g / cm³ can be cited as an example. 3 ~0.96g / cm 3 From the viewpoint of exhibiting moderate crystallinity and imparting rigidity to the composite fiber, 0.93 g / cm³ is preferred. 3 ~0.96g / cm 3 .

[0049] The carbon content derived from biomass in the polyethylene resin of this invention is not particularly limited, but is preferably 20% to 90%, more preferably 30% to 70%, and even more preferably 40% to 50%. If the carbon content derived from biomass in the polyethylene resin is 20% or more, it can not only suppress the consumption of fossil resources, but also impart softness to the nonwoven fabric, so it is preferred. If it is 90% or less, a fluffy nonwoven fabric can be obtained, so it is preferred.

[0050] Furthermore, the melt mass flow rate (hereinafter referred to as MFR) of the suitable polyethylene resin is not particularly limited, but is preferably 10 g / 10 min to 40 g / 10 min, more preferably 16 g / 10 min to 20 g / 10 min, and even more preferably 17 g / 10 min to 19 g / 10 min. If the MFR of the polyethylene resin is 10 g / 10 min or more, stable workability can be obtained, so it is preferred. If it is 40 g / 10 min or less, crystallization of the polyester resin can be promoted, and a fluffy nonwoven fabric can be obtained, so it is preferred. The physical properties of the polyethylene resin other than the MFR, such as Q value (weight average molecular weight / number average molecular weight), Rockwell hardness, number of branched methyl chains, etc., are not particularly limited as long as they meet the necessary conditions of the present invention.

[0051] The second component is not particularly limited as long as it contains polyethylene resin, but preferably contains 80% or more by mass of polyethylene resin, more preferably 90% or more by mass of polyethylene resin. Additives exemplified in the first component may be appropriately included as needed, without impairing the effects of the invention.

[0052] (Thermo-fusion bondable composite fiber)

[0053] As for the combination of components constituting the heat-melting composite fiber (hereinafter, sometimes referred to as "composite fiber") of the present invention, there is no particular limitation as long as the first component contains a polyester resin and the second component contains a polyethylene resin with a melting point lower than that of the first component, and the first and second components described above can be selected. Examples of specific combinations of the first and second components include polyethylene terephthalate / high-density polyethylene, polyethylene terephthalate / linear low-density polyethylene, polyethylene terephthalate / low-density polyethylene, polybutylene terephthalate / high-density polyethylene, or polylactic acid / high-density polyethylene. A preferred combination is polyethylene terephthalate / high-density polyethylene.

[0054] The carbon content of the biomass-derived composite fiber in this invention is not particularly limited, but is preferably 10% or more, more preferably 15% to 60%, and even more preferably 25% to 40%. If the carbon content of the biomass-derived composite fiber is 10% or more, the consumption of fossil resources can be suppressed, so it is preferred. If it is 60% or less, it is easier to maintain the original physical properties of the resin, and the nonwoven fabric can have fluffiness and softness, so it is preferred.

[0055] The composite fiber of the present invention is not particularly limited, but is preferably a sheath-core type heat-fused composite fiber with a first component as the core component and a second component as the sheath component. Preferably, the second component is a composite structure that completely covers the surface of the composite fiber, and more preferably, it is a concentric or eccentric sheath-core structure. Furthermore, the cross-sectional shape of the composite fiber can be any of the following: circular or elliptical, triangular or quadrangular, star-shaped or octagonal, or hollow.

[0056] There are no particular limitations on the composition ratio when the first component and the second component are combined, but a first component / second component ratio of 20 / 80 to 80 / 20 (by weight) is preferred, and a ratio of 40 / 60 to 70 / 30 (by weight) is even more preferred. By setting the composition ratio within the range described above, a good balance of strength, bulkiness, and processability of the nonwoven fabric is achieved, and therefore it is preferred.

[0057] The fineness of the composite fiber in this invention is not particularly limited, but is preferably 2.2 dtex or less, more preferably 0.5 dtex to 2.1 dtex, and even more preferably 1.6 dtex to 1.8 dtex. If the fineness of the composite fiber is 2.2 dtex or less, satisfactory softness or hand feel can be obtained, especially as a nonwoven fabric for hygiene materials.

[0058] The tensile strength of the composite fiber is not particularly limited. For example, for composite fibers used in absorbent articles, it is preferably 1.0 cN / dtex to 4.0 cN / dtex, more preferably 1.5 cN / dtex to 2.5 cN / dtex. If the tensile strength of the composite fiber is 1.0 cN / dtex or higher, a nonwoven fabric with sufficient strength can be obtained; if it is 4.0 cN / dtex or lower, the softness or hand feel of the nonwoven fabric can be improved. Furthermore, the elongation at break of the composite fiber is not particularly limited, but is preferably 30% to 170%, more preferably 50% to 150%, and even more preferably 60% to 120%. If the elongation at break of the composite fiber is 30% or higher, the softness or hand feel of the nonwoven fabric can be improved. Therefore, it is preferable that if it is 170% or lower, the rigidity of the composite fiber increases, which can improve the bulkiness of the nonwoven fabric.

[0059] Furthermore, there are no particular limitations regarding the crimping of composite fibers. The presence or absence of crimping, the number of crimps, the crimp rate, the residual crimp rate, and the crimp elastic modulus can be appropriately selected, taking into account factors such as the web-forming method or the specifications of the web-forming equipment, the productivity of the nonwoven fabric, or the required physical properties. Additionally, there are no particular restrictions on the shape of the crimping; serrated mechanical crimping, spiral crimping, or ohmic three-dimensional crimping can be appropriately selected. Moreover, crimping can be explicit or implicit in thermally bonded composite fibers.

[0060] The heat of melting of the polyester resin in the composite fiber of the present invention is not particularly limited, but is preferably 24 J / g or more, more preferably 26 J / g or more. The heat of melting of the polyester resin in the composite fiber is considered to reflect the crystallinity of the polyester resin in the composite fiber. By setting it to 24 J / g or more, the rigidity of the composite fiber is increased, which can impart fluffiness and softness to the nonwoven fabric. Furthermore, the upper limit of the heat of melting of the polyester resin in the composite fiber is not particularly limited, but is actually 35 J / g or less.

[0061] The fiber length of the heat-bonding composite fiber in this invention is not particularly limited, but is preferably 3 mm or more, and more preferably 30 mm to 64 mm. If it is within this range, it is easy to obtain a web with excellent fiber opening properties or texture in the web forming process using a carding method or the like, and a nonwoven fabric with uniform physical properties can be obtained, so it is preferred.

[0062] (Manufacturing method of thermo-fusion bondable composite fiber)

[0063] There is no particular limitation on the method for manufacturing the heat-fusion composite fiber of the present invention. Any known method for manufacturing heat-fusion composite fibers can be used. The method described later can be used as an example of a method for manufacturing the heat-fusion composite fiber with high productivity and high yield.

[0064] (Spinning process)

[0065] A polyester resin, which is the raw material for the composite fiber of the present invention, is disposed in a first component, and a polyethylene resin having a melting point lower than that of the first component is disposed in a second component. An unextended fiber composed of the first component and the second component is produced by melt spinning.

[0066] There are no particular restrictions on the temperature conditions during melt spinning, but the spinning temperature is preferably 250°C or higher, more preferably 280°C or higher, and even more preferably 300°C or higher. If the spinning temperature is 250°C or higher, it is preferable to reduce the number of filament breaks during spinning and to easily remove unextended filaments remaining after stretching, thus facilitating finer fiber processing. These effects are more pronounced at 280°C or higher, and even more pronounced at 300°C or higher. The upper limit of the temperature is not particularly limited as long as it is a suitable temperature for spinning.

[0067] Furthermore, there is no particular limitation on the spinning speed, but it is preferably 300 m / min to 1500 m / min, and more preferably 400 m / min to 1000 m / min. If the spinning speed is 300 m / min or higher, the amount of unextended yarn produced per hole when obtaining an arbitrary spinning fineness increases, thus achieving satisfactory productivity, which is preferable in this respect.

[0068] (Extended process)

[0069] In the stretching process, the unstretched fibers obtained under the aforementioned conditions are stretched. The stretching temperature is 30°C to 70°C higher than the glass transition temperature of the polyester resin constituting the first component and lower than the melting point of the polyethylene resin constituting the second component, preferably 35°C to 60°C higher than the glass transition temperature of the polyester resin and 5°C lower than the melting point of the polyethylene resin.

[0070] Here, the term "stretching temperature" refers to the temperature of the fiber at the starting point of stretching. If the stretching temperature is "the glass transition temperature of the polyester resin as the first component + 30°C" or higher, the aforementioned effect can be achieved even with high strain rates, i.e., high stretching ratios, and is therefore preferred. Furthermore, the stretching temperature needs to be set below the melting point of the polyethylene resin as the second component and to suppress instability in the stretching process caused by the fusion of fibers. For example, when stretching unstretched fibers in which polyethylene terephthalate with a glass transition temperature of 70°C is incorporated into the first component and high-density polyethylene with a melting point of 130°C is incorporated into the second component, a stretching temperature of 100°C or higher and below 130°C is set. If the stretching temperature is 100°C or higher, the heat relative to the fiber increases, and the difference in stretchability between the polyester resin and the polyethylene resin decreases. This reduces concerns about sheath-core peeling during the carding process in the nonwoven fabric manufacturing process.

[0071] The elongation ratio is not particularly limited, but is preferably 2 to 7 times, and more preferably 4 to 6 times. By setting the elongation ratio within the aforementioned range, the balance between the fineness and stiffness of the composite fiber is improved. In addition, nonwoven fabrics with excellent bulkiness and softness are easily obtained, thereby enabling the production of composite fibers with high productivity.

[0072] (Curling process)

[0073] The extended fibers obtained in the stretching process can also be mechanically crimped using a crimping machine or similar device. The number of crimps applied in the crimping process is not particularly limited, but is preferably 10 sq / 2.54 cm to 25 sq / 2.54 cm. This can be adjusted, for example, by appropriately changing the pressure in the packing box of the crimping machine.

[0074] (Heat treatment process)

[0075] The stretched fibers obtained in the stretching process can be heat-treated. By performing heat treatment after stretching, the crystallinity of the polyester resin, which is the first component of the heat-welding composite fiber, increases, thereby improving the bulkiness of the nonwoven fabric. There is no particular limitation on the heat treatment temperature, but it is preferably carried out in a temperature range that is 30°C to 70°C higher than the glass transition temperature of the polyester resin and lower than the melting point of the polyethylene resin.

[0076] (Cutting process)

[0077] When processing the composite fibers of the present invention into nonwoven fabrics, in the case of a carding process, the composite fibers need to be cut to any length in order to pass through the carding machine. From the viewpoint of fineness or the throughput performance of the carding machine, the length of the composite fibers to be cut is preferably 30 mm to 64 mm.

[0078] (Fiber treatment agent application process)

[0079] In addition, the surface of the composite fiber of the present invention can be treated with various fiber treatment agents, thereby imparting functions such as hydrophilicity, hydrophobicity, electrostatic properties, surface smoothness, and wear resistance.

[0080] Regarding the application process of fiber treatment agents, examples include applying the fiber treatment agent using a kissroll when collecting unstretched fibers, and applying the fiber treatment agent using a touch roll, impregnation, spraying, or other methods during and / or after stretching.

[0081] (Non-woven fabric)

[0082] The nonwoven fabric of the present invention contains the aforementioned heat-fused composite fibers, thus suppressing the consumption of fossil resources and exhibiting excellent bulkiness and softness.

[0083] The carbon content of the biomass-derived nonwoven fabric in this invention is not particularly limited, but from the viewpoint of suppressing the consumption of fossil resources, it is preferably 10% or more, more preferably 15% to 60%, and even more preferably 25% to 40%. To obtain such a biomass-derived carbon content of 10% or more, composite fibers with a biomass-derived carbon content of 10% or more can be used alone, or they can be mixed with other fibers to achieve a total biomass-derived carbon content of 10% or more. Other fibers may include, for example, natural fibers (wood fibers, etc.), regenerated fibers (rayon, etc.), semi-synthetic fibers (acetate, etc.), chemical fibers, synthetic fibers (polyester, acrylic, nylon, vinyl chloride, etc.). The mixing ratio of fibers other than this heat-bonding composite fiber is not limited as long as it does not impair the effect of this invention; for example, it can be set to 1% to 50% by weight.

[0084] There is no particular limitation on the unit area weight of nonwoven fabric, but it is preferably 15 g / m², especially when nonwoven fabric is used as a sanitary material. 2 ~40g / m 2 More preferably 18g / m 2 ~30g / m 2 If the weight per unit area is 15g / m² 2 The above can maintain texture or buffering properties and inhibit backflow, therefore, 40g / m³ is preferred. 2 The following properties can maintain surface smoothness or air permeability and liquid permeability, and are therefore preferred.

[0085] There is no particular limitation on the specific volume of nonwoven fabric, but in the case of nonwoven fabric used as a sanitary material, 30 cm³ is preferred. 3 / g~100cm 3 / g, more preferably 50cm 3 / g~70cm 3 / g. Specific volume is a parameter used as an indicator of bulkiness; the larger the specific volume, the more bulky the nonwoven fabric. For example, a specific volume of 30cm³... 3 A weight of / g or more will yield a fluffy material suitable for use as a sanitary material; if it is 100cm 3 When the density is below / g, the strength of the nonwoven fabric increases, and the nonwoven fabric does not become too thick. It has excellent processability into sanitary materials and is therefore preferred.

[0086] The strength in the long direction (machine direction, MD) of the nonwoven fabric is not particularly limited, but is preferably 35 N / 50 mm or more, and more preferably 45 N / 50 mm or more. If the MD strength of the nonwoven fabric is 35 N / 50 mm or more, its processability into sanitary materials is excellent, and therefore it is preferred.

[0087] The nonwoven fabric of the present invention may comprise a single-layer nonwoven fabric, or may be composed of two or more nonwoven fabrics with different fineness, composition, or density of the composite fibers used. When two or more nonwoven fabrics are layered, for example, by layering nonwoven fabrics with different fineness of composite fibers, a nonwoven fabric is produced in which the size of the gaps between the fibers varies in the thickness direction of the nonwoven fabric, allowing control over liquid permeability or liquid permeability speed, surface feel, etc. Furthermore, for example, by layering nonwoven fabrics with different compositions of composite fibers, a nonwoven fabric is produced in which the hydrophilicity and hydrophobicity of the nonwoven fabric vary in the thickness direction of the nonwoven fabric, allowing control over liquid permeability or liquid permeability speed.

[0088] Furthermore, the nonwoven fabric of the present invention is not particularly limited and can be laminated with other nonwoven fabrics or sheets such as hot-air nonwoven fabrics, air-laid nonwoven fabrics, spunbond nonwoven fabrics, meltblown nonwoven fabrics, spunlace nonwoven fabrics, needle-punched nonwoven fabrics, films, meshes, or webs. Through lamination, liquid permeability or liquid permeability speed, liquid return properties, etc., can be controlled. As for the lamination method, it is not particularly limited; examples include lamination using adhesives such as hot melt adhesives, and lamination using thermal bonding methods such as hot air or hot embossing.

[0089] Nonwoven fabrics may be subjected to shaping, perforation, electrostatic processing, waterproofing, hydrophilic processing, antibacterial processing, ultraviolet absorption processing, near-infrared absorption processing, or electret processing, etc., as appropriate, without impairing the effects of the present invention.

[0090] (Manufacturing method of nonwoven fabric)

[0091] There are no particular limitations on the manufacturing method of nonwoven fabrics. Examples include forming a web containing the aforementioned heat-fusion composite fibers and integrating them through heat or interlacing.

[0092] The method of forming the web is not particularly limited. It can be a long fiber web formed by spunbonding, meltblowing, or tow opening, or a short fiber web formed using short fibers (man-made fibers or chopped fibers) and methods such as carding, air-jet forming, or wet forming. From the viewpoint of imparting bulkiness and softness to the nonwoven fabric, carding or air-jet forming is preferred, and carding is more preferred. Furthermore, in this invention, the term "web" refers to a fiber aggregate in which fibers are not not entangled, and the intersection of the heat-fused composite fibers refers to the unfused state.

[0093] There are no particular limitations on the method of integrating the web through heat or interlacing; examples include hot air method, hot calendering method, water flow interlacing method, or needle punching method. From the viewpoint of imparting fluffiness and softness to the nonwoven fabric, the hot air method is preferred. As for the hot air method, any known equipment and conditions can be used, such as a heat treatment device (e.g., a hot air through-type heat treatment machine or a hot air blowing heat treatment machine) that uses a heat treatment device including a transport support body that supports the transport web to thermally fuse the composite fibers together.

[0094] The heat-bonding composite fibers of the present invention can be used, for example, in hygiene materials such as diapers, sanitary napkins, or incontinence pads; medical materials such as masks, gowns, or surgical gowns; interior decoration materials such as wall sheets, window paper, or interior flooring materials; household-related materials such as cover cloths, wipers, or garbage covers; toilet products such as disposable toilet seats or toilet covers; pet supplies such as pet sheets, pet diapers, or pet towels; industrial materials such as wiping materials, filters, cushioning materials, oil-absorbing materials, or ink tank absorbents; covering materials; coarse wool drapes; bedding materials; and nursing care products—in various fiber products that require fluffiness and softness while suppressing the consumption of fossil resources.

[0095] [Example]

[0096] The present invention will be further described in detail below through embodiments, but the scope of the present invention is not limited thereto.

[0097] The physical property evaluation in this invention is performed using the method shown below.

[0098] <Carbon content derived from biomass>

[0099] The total carbon and other components of the sample were determined using an accelerator mass spectrometer (AMS) (a combination of a tandem accelerator and a mass spectrometer). 14 The carbon content. Based on the total carbon in the sample and 14The carbon content is calculated using the following formula to determine the percentage of biomass-derived carbon in the sample.

[0100] Carbon content derived from biomass (%) = (carbon content derived from biomass in the sample) 14 C) Amount / Total carbon content in the sample) × 100

[0101] <Intrinsic viscosity of polyester resins>

[0102] The measurements were taken in accordance with Japanese Industrial Standards (JIS) K 7367-1.

[0103] <MFR of polyethylene resins>

[0104] The melt mass flow rate (MFR) was determined according to JIS K 7210. The determination was carried out according to conditions D (test temperature 190°C, load 2.16 kg) in Table 1 of Appendix A.

[0105] < Fineness of unstretched fibers, fineness of heat-fused composite fibers, breaking strength, and elongation at break>

[0106] The determination was carried out in accordance with JIS-L-1015.

[0107] <Heat of melting of polyester resin in thermo-meltable composite fibers>

[0108] The heat of fusion of the polyester resin in the composite fiber was determined using a PerkinElmer Japan (DSC) 8500 calorimeter in the following order: First, the composite fiber was cut to a mass of 4.20 mg to 4.80 mg and filled into a sample dish to cover it. Then, under N2 purging, the temperature was increased at a rate of 10 °C / min from 30 °C to 300 °C to obtain a melt flow chart. The obtained chart was analyzed, and the heat of fusion of the polyester resin was calculated based on the area of ​​the endothermic peak in the range of 245 °C to 250 °C.

[0109] <Weight per unit area of ​​nonwoven fabric>

[0110] Cut three pieces of nonwoven fabric into a 10cm×10cm square, measure the weight of each piece, convert it to the weight per unit area, and take the average of the obtained values ​​as the weight per unit area of ​​the nonwoven fabric.

[0111] <The fluffiness of nonwoven fabrics>

[0112] Using a digital thickness gauge manufactured by Toyo Seiki, a pressure element (load) with a diameter of 35mm is applied, resulting in a thickness of 3.5g / cm². 2 The pressure is measured, and the thickness is determined at this point. The specific volume is calculated using the following formula based on the measured thickness.

[0113] Specific volume (cm) 3 / g) = Thickness (mm) ÷ Weight per unit area (g / m²) 2 )×1000

[0114] <MD strength of nonwoven fabric>

[0115] Using an Autograph (AGX-J) manufactured by Shimadzu Corporation, the maximum strength of the nonwoven fabric is determined by stretching a sample cut long along its long side in the shape of 50mm×150mm with a chuck distance of 100mm and a stretching speed of 100mm / min.

[0116] <The softness of non-woven fabrics>

[0117] Cut the nonwoven fabric into 150mm x 150mm pieces. In terms of surface smoothness, cushioning, and drape, conduct a functional test ("good" or "poor") through a group discussion of 5 people. Determine the softness of the nonwoven fabric according to the following 3 stages.

[0118] ◎: All 5 people were rated "Good", which indicates excellent flexibility.

[0119] ○: 1 person is "poor", which can be judged as acceptable softness.

[0120] △: 2 to 3 people are "poor", which can be judged as slightly poor softness.

[0121] ×: 4 or more people is considered "poor", indicating poor flexibility.

[0122] The thermoplastic resins used in the examples and comparative examples are as described below.

[0123] <Thermoplastic Resin 1>

[0124] Biomass-derived polyethylene terephthalate (abbreviated as: bioPET) with an intrinsic viscosity of 0.65, a glass transition point of 70°C, and a carbon content of 30% derived from biomass.

[0125] <Thermoplastic Resin 2>

[0126] Polyethylene terephthalate (PET) derived from fossil resources, with an intrinsic viscosity of 0.64, a glass transition point of 70°C, and a carbon content of 0% derived from biomass.

[0127] <Thermoplastic Resin 3>

[0128] The density is 0.96 g / cm³. 3 Biomass-derived high-density polyethylene (abbreviated symbol: bioPE) with an MFR of 20g / 10min, a melting point of 130℃, and a carbon content of 94% derived from biomass.

[0129] <Thermoplastic Resin 4>

[0130] The density is 0.96 g / cm³. 3 High-density polyethylene (abbreviated symbol: fossil PE) derived from fossil resources, with an MFR of 16g / 10 minutes, a melting point of 130℃, and a carbon content of 0% derived from biomass.

[0131] [Examples 1-6, Comparative Examples 1-4]

[0132] The heat-bonding composite fibers and nonwoven fabrics of the Examples and Comparative Examples were manufactured according to the conditions shown in Tables 1 and 2.

[0133] (Manufacturing of thermo-fusion bonded composite fibers)

[0134] Using the resins shown in Tables 1 and 2, at a spinning temperature of 305°C, unextended fibers with a concentric sheath-core structure, where the first component is disposed on the core side and the second component is disposed on the sheath side, are obtained by spinning at the first component / second component ratio (by weight) shown in Table 1.

[0135] Using a stretching machine, the obtained unstretched fibers were stretched under the conditions shown in Tables 1 and 2. Then, they were wound up with a crimp of 16 mm / 2.54 cm, heat-treated for 5 minutes at the heat treatment temperature shown in Table 1, and cut to a fiber length of 44 mm to obtain heat-fused composite fibers.

[0136] (Non-woven fabric processing)

[0137] The obtained heat-fusion composite fibers are mounted on a roller carding machine to collect a fiber web. A 100cm×30cm section is cut from the fiber web and heat-treated using a hot air circulation heat treatment machine at a processing temperature of 130℃ to heat-fuse the sheath components, thereby obtaining a nonwoven fabric.

[0138] The manufacturing conditions and physical property evaluation results of each embodiment and comparative example are summarized in Tables 1 and 2.

[0139] [Table 1]

[0140]

[0141] [Table 2]

[0142]

[0143] Based on the results in Tables 1 and 2, in Examples 1 to 6 of the present invention, the ratio of biomass-derived polyethylene resin to fossil-derived polyethylene resin as the polyethylene resin was 20:80 to 90:10. This type of thermoforming composite fiber has a high carbon content derived from biomass, and even with finer fineness, the nonwoven fabric remains fluffy and possesses satisfactory softness. In particular, in Examples 1 to 3, the composite fibers have a small fineness and excellent softness.

[0144] On the other hand, in the composite fiber of Comparative Example 1, the proportion of biomass-derived polyethylene resin was high, resulting in a small specific volume (low bulk). This is believed to be due to the high proportion of biomass-derived polyethylene resin, which leads to a significant decrease in molecular weight during resin melting, resulting in insufficient extensibility and a decrease in the crystallinity of the polyester resin. Furthermore, lowering the stretching temperature to increase specific volume (improving bulk) results in increased fineness and compromised softness (Comparative Example 2). In contrast, the composite fiber of Comparative Example 3 had a low proportion of biomass-derived polyethylene resin, resulting in slightly poorer bulk and softness, making it difficult to comprehensively apply as a sanitary material. Comparative Example 4, which did not contain biomass-derived resin, achieved acceptable bulk, but not only was its softness slightly worse, but its low carbon content from biomass also failed to curb the depletion of fossil resources.

[0145] [Industry availability]

[0146] The thermally bondable composite fiber of this invention, by blending polyethylene resin derived from biomass and polyethylene resin derived from fossil resources as the second component in an appropriate ratio, provides a nonwoven fabric that inhibits the consumption of fossil resources and possesses excellent bulk and softness. Therefore, it can be used in hygiene materials such as diapers, sanitary napkins, or incontinence pads; medical materials such as masks, gowns, or surgical gowns; interior decoration materials such as wall coverings, window paper, or indoor flooring materials; household materials such as tent fabrics, cleaning cloths, or garbage covers; bathroom products such as disposable toilet seats or toilet seat pads; pet supplies such as pet mats, pet diapers, or pet towels; industrial materials such as wiping materials, filters, cushioning materials, oil-absorbing materials, or ink absorbents; covering materials; coarse wool fabrics; bedding materials; and nursing products—in various fiber products that inhibit the consumption of fossil resources and require bulk and softness.

Claims

1. A hot-melt adhesive composite fiber, which is a hot-melt adhesive composite fiber in which a first component contains a polyester-based resin and a second component contains a polyethylene-based resin having a lower melting point than the first component, the polyester-based resin is polyethylene terephthalate, the polyethylene-based resin is high-density polyethylene, and in the polyethylene-based resin, the blending ratio of a biomass-derived polyethylene-based resin to a fossil resource-derived polyethylene-based resin is 20:80 to 90:10, the blending ratio is a weight ratio, and the carbon content of the biomass-derived polyethylene-based resin in the polyethylene-based resin of the second component is 23.5% to 65.8%.

2. The hot-melt adhesive composite fiber according to claim 1, wherein the carbon content of the biomass-derived polyethylene-based resin in the hot-melt adhesive composite fiber is 10% or more.

3. The hot-melt adhesive composite fiber according to any one of claims 1 or 2, wherein the carbon content of the biomass-derived polyethylene-based resin in the polyester-based resin is 30% or less.

4. The hot-melt adhesive composite fiber according to claim 1 or 2, wherein the fineness of the hot-melt adhesive composite fiber is 2.2 dtex or less.

5. The hot-melt adhesive composite fiber according to claim 1 or 2, wherein the heat of fusion of the polyester-based resin in the hot-melt adhesive composite fiber is 24 J / g or more.

6. The hot-melt adhesive composite fiber according to claim 1 or 2, which is a sheath-core type hot-melt adhesive composite fiber in which the first component is a core component and the second component is a sheath component.

7. A nonwoven fabric comprising the hot-melt adhesive composite fiber according to any one of claims 1 to 6.

8. An absorbent article using the hot-melt adhesive composite fiber according to any one of claims 1 to 6.

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