Heat-fusible composite fibers and nonwoven fabrics using the same

Abstract

To provide a heat-fusible composite fiber that suppresses consumption of fossil resources and imparts both bulkiness and flexibility to non-woven fabrics, and a non-woven fabric using the same.SOLUTION: There is provided a heat-fusible composite fiber containing a polyester-based resin as a first component and a polyethylene-based resin having a lower melting point than that of the first component as a second component, in which a mixing ratio (weight ratio) between a biomass-derived polyethylene-based resin and a fossil-resource-derived polyethylene-based resin in the polyethylene resin is 20:80 to 90:10.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a heat-fusible composite fiber containing biomass-derived components and a nonwoven fabric obtained using the same. [Background technology]

[0002] Conventionally, heat-fusible composite fibers, which can be molded by heat fusion using the thermal energy of hot air or heated rolls, are widely used in sanitary materials such as diapers, napkins, and pads, as well as in household goods and industrial materials such as filters, because it is easy to obtain nonwoven fabrics with excellent bulkiness and flexibility. In particular, sanitary materials come into direct contact with human skin and need to quickly absorb liquids such as urine and menstrual blood, so bulkiness and flexibility are of extremely high importance. Typical methods for obtaining bulkiness include using high-rigidity resins or increasing rigidity by stretching at high magnification, but in that case, the resulting nonwoven fabric has reduced flexibility. On the other hand, if flexibility is prioritized, the resulting nonwoven fabric has reduced bulkiness and poor liquid absorbency.

[0003] Therefore, methods have been proposed to obtain fibers and nonwoven fabrics that can achieve both bulkiness and flexibility. Patent Document 1 discloses a heat-fusible composite fiber in which the first component is a polyester resin and the second component is a polyolefin resin with a lower melting point than the first component, and it is stated that a bulky and flexible nonwoven fabric can be obtained by using this fiber.

[0004] Incidentally, in recent years, with the growing demand for the creation of a circular economy, there is a desire to move away from fossil resources in the materials field, just as there is a desire for energy, and the use of biomass-derived materials is attracting attention. Biomass is an organic compound produced by photosynthesis from carbon dioxide and water (see, for example, Patent Documents 2 and 3), and if such biomass-derived materials are used as starting materials, the amount of fossil resources used 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, these amounts are equal to the amount of carbon dioxide and water before they were taken up by plants through photosynthesis, making it possible to create a recycling system or carbon neutrality.

[0005] Against this backdrop, composite fibers made from biomass-derived materials have been proposed in the field of sanitary materials. Patent document 4 discloses PET and PE composite fibers made from biomass-derived materials, and states that it reduces the consumption of fossil resources and that a nonwoven fabric with a uniform structure can be obtained by polymerizing various polymers with PE.

[0006] Generally, biomass-derived resins are thought to have no difference in quality because their chemical structure is the same as those derived from conventional fossil resources. However, the raw material monomers of biomass-derived resins may contain impurities that could not be removed during the manufacturing process, resulting in reduced heat resistance and making them difficult to use in the same way as resins derived from fossil resources. In particular, in the manufacture of nonwoven fabrics for sanitary materials, one method to obtain good flexibility and texture is to reduce the fiber fineness. However, when conventional biomass-derived resins are used, it is difficult to obtain fine-fiber heat-fusible composite fibers, and even if fine-fiber heat-fusible composite fibers are obtained, the nonwoven fabric obtained using those fibers will have a very low bulk. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2017-214662 [Patent Document 2] Japanese Patent Publication No. 2009-091694 [Patent Document 3] Japanese Patent Publication No. 2008-150759 [Patent Document 4] Japanese Patent Publication No. 2012-140728 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Thus, with conventional technology, in order to obtain a nonwoven fabric that achieves a satisfactory level of bulkiness and flexibility for suitable use as a sanitary material, it is necessary to use materials derived solely from fossil resources. As a result, a nonwoven fabric that achieves both bulkiness and flexibility while reducing the consumption of fossil resources has not yet been obtained.

[0009] This invention was made against the backdrop of the above-mentioned prior art, and its purpose is to provide a heat-fusible composite fiber that reduces the consumption of fossil resources and gives nonwoven fabrics both bulkiness and flexibility, and a nonwoven fabric using the same. [Means for solving the problem]

[0010] The inventors diligently conducted research to solve the above problems. As a result, they discovered that the above problems can be solved by blending a polyethylene resin derived from biomass and a polyethylene resin derived from fossil resources in an appropriate ratio as the polyethylene resin in a heat-fusible composite fiber composed of a polyester resin as the first component and a polyethylene resin with a lower melting point than the first component as the second component, thus completing the present invention.

[0011] In other words, the present invention is constructed as follows. [1]A heat-sealable composite fiber composed of a polyester-based resin as the first component and a polyethylene-based resin having a lower melting point than the first component, wherein in the polyethylene-based resin, the blending ratio (weight ratio) of the biomass-derived polyethylene-based resin to the fossil resource-derived polyethylene-based resin is 20:80 to 90:10. [2]The heat-sealable composite fiber according to [1], wherein the biomass-derived carbon content in the polyethylene-based resin is 20 to 90%. [3]The heat-sealable composite fiber according to [1] or [2], wherein the biomass-derived carbon content in the heat-sealable composite fiber is 10% or more. [4]The heat-sealable composite fiber according to any one of [1] to [3], wherein the biomass-derived carbon content in the polyester-based resin is 30% or less. [5]The heat-sealable composite fiber according to any one of [1] to [4], wherein the fineness of the heat-sealable composite fiber is 2.2 dtex or less. [6]The heat-sealable composite fiber according to any one of [1] to [5], wherein the heat of fusion of the polyester-based resin in the heat-sealable composite fiber is 24 J / g or more. [7]The heat-sealable composite fiber according to any one of [1] to [6], wherein the heat-sealable composite fiber is a sheath-core type heat-sealable composite fiber having the first component as the core component and the second component as the sheath component. [8]The heat-sealable composite fiber according to any one of [1] to [7], wherein the polyester-based resin is polyethylene terephthalate and the polyethylene-based resin is high-density polyethylene. [9]A non-woven fabric containing the heat-sealable composite fiber according to any one of [1] to [8].

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

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a heat-sealable composite fiber that suppresses the consumption of fossil resources and gives both bulkiness and flexibility to a non-woven fabric.

Modes for Carrying Out the Invention

[0013] The heat-fusible composite fiber of the present invention is characterized in that the first component is a polyester resin and the second component is a polyethylene resin having a lower melting point than the first component, and the polyethylene resin is characterized in that the blending ratio (by weight) of biomass-derived polyethylene resin and fossil resource-derived polyethylene resin is 20:80 to 90:10.

[0014] (Component 1) The polyester resin constituting the first component in the present 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, and preferred aliphatic polyester resins include polylactic acid and polybutylene succinate. These polyester resins may be homopolymers as well as copolymerized polyesters (copolyesters). In this case, 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 as copolymer components. Polybutylene terephthalate adipate is an example of such copolymer. Furthermore, two or more of these polyester resins may be mixed and used. Among these, considering raw material costs, bulkiness of the nonwoven fabric, and thermal stability of the resulting fibers, an unmodified polymer composed solely of polyethylene terephthalate is preferred as the first component.

[0015] When the polyester resin is an aromatic polyester resin, it can be obtained, for example, by condensation polymerization from a diol and a dicarboxylic acid. Examples of dicarboxylic acids used in the condensation polymerization 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-cyclohexanedimethanol.

[0016] The biomass-derived carbon content in the polyester resin in the present invention is not particularly limited, but is preferably 30% or less, more preferably 2-28%, and even more preferably 6-24%. A biomass-derived carbon content of 2% or more in the polyester resin is preferable because it can reduce the consumption of fossil resources, and a biomass-derived carbon content of 30% or less is preferable because it makes it easier to maintain the original physical properties of the polyester resin and allows the nonwoven fabric to have bulkiness and flexibility.

[0017] Here, the biomass-derived carbon content refers to radioactive carbon ( 14 C) This is the value of the carbon content derived from biomass measured by the measurement. Atmospheric carbon dioxide contains 14 Because it contains a certain percentage of carbon (107 pMC (percent modern carbon)), plants that take in carbon dioxide from the atmosphere to grow, such as corn, 14 It is also known that the C content is approximately 107 pMC. 14 Carbon dioxide (C) has a half-life of 5,370 years and returns to nitrogen atoms, and it takes 226,000 years for it to completely decay. Therefore, fossil fuels such as coal, oil, and natural gas, which are thought to have been fixed after being absorbed by plants and other organisms in the atmosphere for more than 226,000 years, contain carbon dioxide. 14 It is known that it contains almost no carbon. Therefore, the total carbon atoms in the resin are 14By measuring the proportion of C, the biomass-derived carbon content can be calculated. The method for calculating the biomass-derived carbon content in the resin according to the present invention will be described in detail in the examples below.

[0018] While the polyester resin is not particularly limited, it is preferable that it contains both biomass-derived and fossil-derived polyester resins, as this reduces the consumption of fossil resources, preserves the inherent properties of the polyester resin, and provides bulkiness and flexibility to the nonwoven fabric. From this viewpoint, the blending ratio (by weight) of biomass-derived polyester resin and fossil-derived polyester resin in the polyester resin is not particularly limited, but is preferably 5:95 to 95:5, and more preferably 20:80 to 80:20.

[0019] Here, a biomass-derived polyester resin is defined as a resin that contains biomass-derived carbon, preferably with a biomass-derived carbon content of 10% or more, and more preferably 20% or more. Such a biomass-derived polyester resin may be a polymer consisting only of biomass-derived monomers, or a copolymer of biomass-derived monomers and fossil resource-derived monomers. For example, if the polyester resin is an aromatic polyester resin, examples include a copolymer of a biomass-derived diol and a biomass-derived dicarboxylic acid, a copolymer of a biomass-derived diol and a fossil resource-derived dicarboxylic acid, and a copolymer of a fossil resource-derived diol and a biomass-derived dicarboxylic acid. Among these, a copolymer of a biomass-derived diol and a fossil resource-derived dicarboxylic acid is preferred from the viewpoint of availability.

[0020] The biomass-derived polyester resin is not particularly limited, and may be obtained by conventionally known methods, or it may be biomass-derived polyethylene terephthalate commercially available from companies such as Far East Spinning Co., Ltd., or biomass-derived polylactic acid commercially available from NatureWorks Inc.

[0021] Furthermore, fossil resource-derived polyester resins refer to polyester resins that do not contain biomass-derived carbon, i.e., those with a biomass-derived carbon content of 0%. Therefore, fossil resource-derived polyester resins are those polymerized solely from monomers derived from fossil resources.

[0022] The first component is not particularly limited as long as it contains a polyester resin, but preferably contains 80% by mass or more of a polyester resin, and more preferably contains 90% by mass or more of a polyester resin. Within the limits that do not hinder the effects of the present invention, additives such as 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 appropriate and as needed.

[0023] (Second component) The polyethylene resin in the present invention is not particularly limited, and examples include high-density polyethylene, linear low-density polyethylene, low-density polyethylene, copolymers of ethylene and other components (e.g., α-olefins), or mixtures thereof. However, from the viewpoint of suppressing the phenomenon in which polyethylene resins exposed on the fiber surface fuse together without completely cooling and solidifying during spinning, it is preferable that the resin be composed solely of high-density polyethylene.

[0024] In the present invention, it is important that the polyethylene resin constituting the second component has a mixing ratio (by weight) of 20:80 to 90:10 between biomass-derived polyethylene resin and fossil resource-derived polyethylene resin. In conventional technology, when only biomass-derived polyethylene resin is used as the polyethylene resin, the resin is subjected to a heat history of nearly 300°C during the melting process, which causes a decrease in viscosity and molecular weight of the resin, resulting in insufficient stretchability. This makes it difficult to achieve both fineness and rigidity in the composite fibers, and it is believed that a flexible and bulky nonwoven fabric could not be obtained. In the present invention, by setting the mixing ratio of biomass-derived polyethylene resin to 90% by weight or less, the decrease in viscosity and molecular weight of the polyethylene resin is suppressed, and the elongation during the formation process of the composite fibers is made appropriate, enabling both fineness and rigidity in the composite fibers. Furthermore, by setting the mixing ratio of biomass-derived polyethylene resin to 20% by weight or more, it is possible not only to improve the biomass-derived carbon content of the composite fibers and reduce the consumption of fossil resources, but also to further improve the flexibility of the nonwoven fabric. From this perspective, the blending ratio (by weight) of biomass-derived polyethylene resin and fossil resource-derived polyethylene resin is preferably 30:70 to 70:30, and more preferably 40:60 to 50:50.

[0025] Here, the biomass-derived polyethylene resin only needs to contain biomass-derived carbon, preferably with a biomass-derived carbon content of 90% or more, and more preferably 94% or more. Such a biomass-derived polyethylene resin may be a polymer consisting only of biomass-derived monomers, or a polymer of biomass-derived monomers and fossil resource-derived monomers. Examples include a polymer of biomass-derived ethylene, a copolymer of biomass-derived ethylene and biomass-derived α-olefins (propylene, butylene, hexene, octene, etc.), a copolymer of biomass-derived ethylene and fossil resource-derived ethylene, a copolymer of biomass-derived ethylene and fossil resource-derived α-olefins, or a copolymer of biomass-derived α-olefins and fossil resource-derived ethylene. In particular, from the viewpoint of suppressing the adhesion of fibers during the molding of composite fibers, the biomass-derived polyethylene resin is preferably a polymer of biomass-derived ethylene or a polymer of biomass-derived ethylene and fossil resource-derived ethylene.

[0026] The biomass-derived polyethylene resin is not particularly limited, and may be obtained by conventionally known methods. For example, it can be produced by fermenting starch or sugar obtained from corn, sugarcane, sweet potatoes, etc., with microorganisms to produce bioethanol, then dehydrating it to produce biomass-derived ethylene, and finally polymerizing it. Alternatively, commercially available biomass-derived polyethylene resins from companies such as Braskem may be used.

[0027] In addition, the fossil resource-derived polyethylene resin means a polyethylene resin that does not contain biomass-derived carbon, that is, the biomass-derived carbon content is 0%. Therefore, the fossil resource-derived polyethylene resin is polymerized only from monomers derived from fossil resources. For example, polymers of ethylene derived from fossil resources and copolymers of ethylene derived from fossil resources and α-olefins derived from fossil resources can be mentioned. Among them, from the viewpoint of suppressing adhesion between fibers during the molding of composite fibers, the fossil resource-derived polyethylene resin is preferably a polymer of ethylene derived from fossil resources.

[0028] The density of the biomass-derived polyethylene resin is not particularly limited, but examples thereof include 0.91 to 0.96 g / cm 3 The density of the fossil resource-derived polyethylene resin is not particularly limited, but examples thereof include 0.91 to 0.96 g / cm 3 From the viewpoint of exhibiting appropriate crystallinity and imparting rigidity to the composite fiber, it is preferably 0.93 to 0.96 g / cm 3

[0029] The biomass-derived carbon content in the polyethylene resin in the present 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 biomass-derived carbon content in the polyethylene resin is 20% or more, it is preferable because it can not only suppress the consumption of fossil resources but also impart flexibility to the non-woven fabric. If it is 90% or less, it is preferable because a bulky non-woven fabric can be obtained.

[0030] ​Furthermore, while there are no particular limitations on the melt mass flow rate (hereinafter abbreviated as MFR) of the polyethylene resin that can be suitably used, it is preferably 10 to 40 g / 10 min, more preferably 16 to 20 g / 10 min, and even more preferably 17 to 19 g / 10 min. An MFR of 10 g / 10 min or more is preferred because it provides stable operability, and an MFR of 40 g / 10 min or less is preferred because it can promote the crystallization of the polyester resin and produce a bulky nonwoven fabric. The physical properties of the polyethylene resin other than the MFR, such as the Q value (weight-average molecular weight / number-average molecular weight), Rockwell hardness, and number of branched methyl chains, are not particularly limited as long as they satisfy the requirements of the present invention.

[0031] The second component is not particularly limited as long as it contains a polyethylene resin, but preferably it contains 80% by mass or more of a polyethylene resin, and more preferably it contains 90% by mass or more of a polyethylene resin. Additives exemplified in the first component may be included as appropriate, as long as they do not hinder the effects of the present invention.

[0032] (Heat-fusible composite fiber) The combination of components constituting the heat-fusible composite fiber (hereinafter sometimes referred to as "composite fiber") in the present invention is not particularly limited, as long as the first component is a polyester resin and the second component is a polyethylene resin having a lower melting point than the first component, and can be selected from the first and second components described above. Specific examples of first / second component combinations 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. Among these, the preferred combination is polyethylene terephthalate / high-density polyethylene.

[0033] The biomass-derived carbon content of the composite fiber in the present invention is not particularly limited, but is preferably 10% or more, more preferably 15-60%, and even more preferably 25-40%. A biomass-derived carbon content of 10% or more in the composite fiber is preferable because it can reduce the consumption of fossil resources, and a content of 60% or less is preferable because it makes it easier to maintain the original properties of the resin and allows the nonwoven fabric to have bulkiness and flexibility.

[0034] The composite fiber of the present invention is not particularly limited, but it is preferably a sheath-core type heat-fusible composite fiber having a first component as a core component and a second component as a sheath component. In particular, it is preferable that the second component completely covers the surface of the composite fiber, and a concentric or eccentric sheath-core structure is more preferable. Furthermore, the cross-sectional shape of the composite fiber can be any of the following: round, such as a circle or ellipse; angular, such as a triangle or square; irregular, such as a star or octave; or hollow.

[0035] While there are no particular restrictions on the composition ratio when combining the first and second components, it is preferable that the ratio of the first and second components be 20 / 80 to 80 / 20 (by weight), and more preferably 40 / 60 to 70 / 30 (by weight). This range of composition ratio is preferable because it tends to result in an excellent balance of strength, bulkiness, and processability of the nonwoven fabric.

[0036] 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 to 2.1 dtex, and even more preferably 1.6 to 1.8 dtex. When the fineness of the composite fiber is 2.2 dtex or less, it is possible to obtain satisfactory flexibility and texture, especially for nonwoven fabrics used in sanitary materials.

[0037] The tensile strength of the composite fiber is not particularly limited, but for composite fibers used in absorbent articles, for example, it is preferably 1.0 to 4.0 cN / dtex, and more preferably 1.5 to 2.5 cN / dtex. If the tensile strength of the composite fiber is 1.0 cN / dtex or higher, it is possible to obtain a nonwoven fabric with sufficient strength, and if it is 4.0 cN / dtex or lower, it is possible to improve the flexibility and texture of the nonwoven fabric. Furthermore, the elongation at break of the composite fiber is not particularly limited, but it 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, it is preferable because it can improve the flexibility and texture of the nonwoven fabric, and if it is 170% or lower, the rigidity of the composite fiber increases, and it is possible to improve the bulkiness of the nonwoven fabric.

[0038] Furthermore, the crimping of the composite fibers is not particularly limited, and the crimping characteristics such as the presence or absence of crimping, the number of crimps, the crimping rate, the residual crimping rate, and the crimping modulus can be appropriately selected considering the web formation method, the specifications of the web formation equipment, the productivity of the nonwoven fabric, and the required physical properties. Also, the shape of the crimping is not particularly limited, and mechanical crimping of a zigzag shape, or three-dimensional crimping of a spiral or ohm shape can be appropriately selected. Moreover, the crimping may be apparent or latent in the heat-fusible composite fibers.

[0039] The heat of fusion of the polyester resin in the composite fiber of the present invention is not particularly limited, but is preferably 24 J / g or more, and more preferably 26 J / g or more. The heat of fusion of the polyester resin in the composite fiber is considered to reflect the degree of crystallinity of the polyester resin in the composite fiber, and setting it to 24 J / g or more improves the rigidity of the composite fiber, making it possible to impart bulkiness and flexibility to the nonwoven fabric. Furthermore, the upper limit of the heat of fusion of the polyester resin in the composite fiber is not particularly limited, but in reality it is 35 J / g or less.

[0040] The fiber length of the heat-fusible composite fiber in the present invention is not particularly limited, but is preferably 3 mm or longer, and more preferably 30 to 64 mm. Within this range, it is easier to obtain a web with excellent fiber opening properties and texture in the web formation process, such as by the carding method, and a nonwoven fabric with uniform physical properties can be obtained, which is therefore preferable.

[0041] (Method for manufacturing heat-fusible composite fibers) The method for producing the heat-fusible composite fiber of the present invention is not particularly limited, and any known method for producing heat-fusible composite fiber may be used. However, the method described below can be exemplified as a method for producing the heat-fusible composite fiber with high productivity and high yield.

[0042] (Spinning process) The present invention provides an undrawn fiber in which a polyester resin, which is the raw material for the composite fiber, is arranged as the first component, and a polyethylene resin having a lower melting point than the first component is arranged as the second component, and the first component and the second component are combined by melt spinning.

[0043] The temperature conditions during melt spinning are not particularly limited, but the spinning temperature is preferably 250°C or higher, more preferably 280°C or higher, and even more preferably 300°C or higher. A spinning temperature of 250°C or higher is preferable because it reduces the number of yarn breaks during spinning and allows for the production of undrawn yarn that retains elongation after drawing, making it easier to achieve finer denier. These effects become more pronounced at 280°C or higher, and even more pronounced at 300°C or higher, which is preferable. The upper limit of the temperature is not particularly limited and can be any temperature at which spinning can be performed satisfactorily.

[0044] Furthermore, while the spinning speed is not particularly limited, it is preferably 300 to 1500 m / min, and more preferably 400 to 1000 m / min. A spinning speed of 300 m / min or higher is preferable because it increases the single-hole discharge amount when trying to obtain undrawn yarn of a desired spinning fineness, thereby achieving satisfactory productivity.

[0045] (Stretching process) The undrawn fibers obtained under the above conditions are subjected to a drawing process. The drawing temperature is 30 to 70°C higher than the glass transition temperature of the polyester resin constituting the first component, and below the melting point of the polyethylene resin constituting the second component. Preferably, it is 35 to 60°C higher than the glass transition temperature of the polyester resin and 5°C or less below the melting point of the polyethylene resin.

[0046] Here, the stretching temperature refers to the temperature of the fiber at the stretching start position. It is preferable that the stretching temperature be "glass transition temperature of the polyester resin, which is the first component + 30°C" or higher, as this allows the effect to be obtained even when stretching at a high strain rate, i.e., at a high magnification. Furthermore, the stretching temperature should be below the melting point of the polyethylene resin, which is the second component, in order to suppress instability in the stretching process due to fusion of fibers. For example, when stretching an unstretched fiber in which polyethylene terephthalate, which has a glass transition temperature of 70°C, is used as the first component and high-density polyethylene, which has a melting point of 130°C, is used as the second component, the stretching temperature should be between 100°C and 130°C. When the stretching temperature is 100°C or higher, the amount of heat applied to the fiber increases, and the difference in stretchability between the polyester resin and the polyethylene resin decreases. This reduces the risk of sheath-core delamination during carding in the nonwoven fabric process.

[0047] The stretching ratio is not particularly limited, but is preferably 2 to 7 times, and more preferably 4 to 6 times. By setting the stretching ratio within the above range, a good balance between the fineness and rigidity of the composite fibers is achieved, making it easier to obtain a nonwoven fabric with excellent bulkiness and flexibility, and further enabling the production of composite fibers with high productivity.

[0048] (Crimping process) Mechanical crimping may be applied to the drawn fibers obtained in the drawing process using a crimper or the like. The number of crimps applied in the crimping process is not particularly limited, but is preferably 10 to 25 crimps / 2.54 cm, and can be adjusted by appropriately changing, for example, the stuffing box pressure in a push-type crimper.

[0049] (Heat treatment process) The stretched fibers obtained in the stretching process may be heat-treated. By heat-treating after stretching, the crystallinity of the polyester resin, which is the first component of the heat-fusible composite fiber, can be increased, thereby improving the bulkiness of the nonwoven fabric. The heat treatment temperature is not particularly limited, but it is preferable to perform it at a temperature of 30 to 70°C or higher, which is above the glass transition temperature of the polyester resin, and below the melting point of the polyethylene resin.

[0050] (Cutting process) When processing a nonwoven fabric using the composite fibers of the present invention, if a carding process is employed, the composite fibers need to be cut to a desired length in order to pass through the carding machine. From the viewpoint of fineness and the passability of the carding machine, the length to which the composite fibers are cut, or cut length, is preferably 30 to 64 mm.

[0051] (Process of applying fiber treatment agent) Furthermore, the composite fibers of the present invention may have their surfaces treated with various fiber treatment agents, thereby imparting functions such as hydrophilicity, water repellency, antistatic properties, surface smoothness, and abrasion resistance. Regarding the process of applying the fiber treatment agent, examples of methods include applying the fiber treatment agent with a kiss roll when the undrawn fibers are taken up, or applying it during and / or after drawing using methods such as the touch roll method, immersion method, or spraying method.

[0052] (Non-woven fabric) Because the nonwoven fabric of the present invention contains the heat-fusible composite fibers described above, it reduces the consumption of fossil resources and is also highly bulky and flexible.

[0053] The biomass-derived carbon content of the nonwoven fabric in the present invention is not particularly limited, but from the viewpoint of reducing the consumption of fossil resources, it is preferably 10% or more, more preferably 15-60%, and even more preferably 25-40% or more. To obtain a nonwoven fabric with a biomass-derived carbon content of 10% or more, only composite fibers with a biomass-derived carbon content of 10% or more may be used, or they may 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 (such as wood fibers), regenerated fibers (such as rayon), semi-synthetic fibers (such as acetate), chemical fibers, and synthetic fibers (such as polyester, acrylic, nylon, and polyvinyl chloride). The mixing ratio of fibers other than such heat-fusible composite fibers is not limited as long as it does not hinder the effects of the present invention, but for example, it can be 1-50% by weight.

[0054] While there are no particular limitations on the basis weight of nonwoven fabrics, when used as nonwoven fabrics for sanitary materials, it is typically 15-40 g / m². 2 Preferably, it is 18-30 g / m 2 It is more preferable that the basis weight is 15g / m². 2 The above is preferable because it can maintain the texture and cushioning properties and suppress liquid return, and is 40g / m². 2 The following conditions are preferable because they allow for the maintenance of surface smoothness, air permeability, and liquid permeability.

[0055] The specific volume of the nonwoven fabric is not particularly limited, but especially when used as a nonwoven fabric for sanitary materials, it is 30 to 100 cm³. 3 It is preferable that the amount be / g, and the length is 50-70 cm. 3 It is more preferable that the specific volume is / g. Specific volume is a parameter used as an indicator of bulkiness; the larger the specific volume, the bulkier the nonwoven fabric is considered to be. Specific volume of 30 cm³ 3 If the amount is 100cm or more, it can be obtained to achieve a bulk height suitable for use as a sanitary material. 3A value of less than / g is preferable because it increases the strength of the nonwoven fabric, prevents it from becoming too thick, and results in excellent processability for use as a sanitary material.

[0056] The longitudinal strength (MD strength) of the nonwoven fabric is not particularly limited, but it is preferably 35 N / 50 mm or more, and more preferably 45 N / 50 mm or more. An MD strength of 35 N / 50 mm or more is preferable because it results in excellent processability for sanitary materials.

[0057] The nonwoven fabric of the present invention may consist of one type (single layer) of nonwoven fabric, or it may consist of two or more types of nonwoven fabrics laminated together, each having different fineness, composition, or density of the composite fibers used. When two or more types of nonwoven fabrics are laminated together, for example, by laminating nonwoven fabrics with different fineness of composite fibers, the size of the gaps formed between the fibers changes in the thickness direction of the nonwoven fabric, thereby allowing control of liquid permeability, liquid permeability, and surface texture. Alternatively, for example, by laminating nonwoven fabrics with different compositions of composite fibers, the hydrophilicity and hydrophobicity of the nonwoven fabric change in the thickness direction, thereby allowing control of liquid permeability and liquid permeability.

[0058] Furthermore, the nonwoven fabric of the present invention is not particularly limited, but may be laminated and integrated with other nonwoven fabrics, films, or sheets such as through-air nonwoven fabrics, airlaid nonwoven fabrics, spunbond nonwoven fabrics, meltblown nonwoven fabrics, spunlace nonwoven fabrics, needle-punched nonwoven fabrics, films, meshes, or nets. By laminating and integrating, it is possible to control liquid permeability, liquid permeability, liquid return properties, etc. There are no particular limitations on the method of lamination and integration, but examples include lamination and integration using adhesives such as hot melt, and lamination and integration using thermal bonding such as through-air or thermal embossing.

[0059] The nonwoven fabric may be subjected to shaping, perforation, antistatic treatment, water-repellent treatment, hydrophilic treatment, antibacterial treatment, ultraviolet absorption treatment, near-infrared absorption treatment, or electret treatment, as appropriate, to the extent that it does not impair the effects of the present invention.

[0060] (Method of manufacturing nonwoven fabrics) The method for manufacturing the nonwoven fabric is not particularly limited, but an example is a method in which a web containing the heat-fusible composite fibers described above is formed and integrated by heat or entanglement.

[0061] The method for forming the web is not particularly limited. It may be a long-fiber web formed by the spunbond method, meltblown method, or tow opening method, or a short-fiber web formed using short fibers (staples or chops) by the carding method, airlaid method, or wet method. However, from the viewpoint of imparting bulkiness and flexibility to the nonwoven fabric, the carding method or airlaid method is preferred, and the carding method is more preferred. In this invention, "web" refers to a fiber aggregate in which fibers are somewhat entangled, and the intersections of heat-fusible composite fibers are not fused.

[0062] The method for integrating the web by heat or entanglement is not particularly limited, and examples include the through-air method, thermal calendering method, water flow entanglement method, or needle punching method. However, the through-air method is preferred from the viewpoint of imparting bulkiness and flexibility to the nonwoven fabric. For the through-air method, known equipment and conditions can be applied, such as a method of heat fusing composite fibers together using a heat treatment device equipped with a conveying support for supporting and transporting the web (for example, a hot air penetration type heat treatment machine or a hot air blowing type heat treatment machine).

[0063] The heat-fusible composite fiber of the present invention can be used in a variety of textile products that require reduced consumption of fossil resources, as well as bulkiness and flexibility, such as sanitary materials like diapers, napkins, or incontinence pads; medical supplies like masks, gowns, or surgical gowns; interior materials like wall sheets, shoji paper, or flooring; lifestyle-related materials like cover cloths, cleaning wipers, or garbage covers; toiletries like disposable toilets or toilet covers; pet supplies like pet sheets, pet diapers, or pet towels; industrial materials like wiping materials, filters, cushioning materials, oil absorbents, or ink tank absorbents; covering materials, humping materials, bedding materials, and nursing care products. [Examples]

[0064] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited thereto.

[0065] The physical properties in this invention were evaluated by the following method. <Biomass-derived carbon content> The sample was analyzed using an accelerator-based mass spectrometer (AMS) (a combination of a tandem accelerator and a mass spectrometer) to determine the total carbon content and 14 The C content was measured. The total carbon and 14 Based on the C content, the biomass-derived carbon content of the sample was calculated using the following formula. Biomass-derived carbon content (%) = (carbon content from biomass in the sample) 14 C) (amount / total amount of carbon in the sample) × 100 <Intrinsic viscosity of polyester resins> Measurements were taken in accordance with JIS K 7367-1. <Polyethylene resin MFR> The melt mass flow rate (MFR) was measured in accordance with JIS K 7210. The measurement was performed according to condition D (test temperature 190°C, load 2.16 kg) in Appendix A, Table 1. <Fineness of undrawn fibers, fineness, breaking strength, and elongation at breaking of heat-fusible composite fibers> Measurements were taken in accordance with JIS-L-1015. <Heat of fusion of polyester resins in heat-fusible composite fibers> The heat of fusion of polyester resin in composite fibers was measured using a differential scanning calorimetry (DSC8500) manufactured by PerkinElmer Japan, following the procedure below. First, composite fibers were cut to a mass of 4.20 to 4.80 mg, packed into a sample pan, and covered. Next, the temperature was measured from 30°C to 300°C in an N2 purge at a heating rate of 10°C / min to obtain a melt chart. The obtained chart was analyzed, and the heat of fusion of the polyester resin was calculated from the area of ​​the endothermic peak in the range of 245°C to 250°C. <Balance weight of nonwoven fabric> Three 10cm x 10cm squares of nonwoven fabric were cut out, their respective weights were measured, converted to weights per unit area, and the average of the resulting values ​​was used as the basis weight of the nonwoven fabric. <Bulkiness of nonwoven fabrics> Using a Toyo Seiki digital nest tester, a pressure element (load) with a diameter of 35 mm was measured at 3.5 g / cm². 2 The pressure was applied, and the thickness at that time was measured. The specific volume was calculated from the measured thickness using the following formula. Specific volume (cm 3 / g) = Thickness (mm) ÷ Basis Weight (g / m 2 ) × 1000 <MD strength of nonwoven fabrics> A sample measuring 50mm x 150mm, cut lengthwise, was subjected to a tensile test using a Shimadzu Autograph (AGX-J) machine with a chuck distance of 100mm and a tensile speed of 100mm / min. The maximum strength measured during this test was defined as the MD strength of the nonwoven fabric. <Flexibility of nonwoven fabrics> Nonwoven fabric was cut into 150mm x 150mm pieces, and a sensory test ("good" or "bad") was conducted by five panelists based on surface smoothness, cushioning, and drape, and the flexibility of the nonwoven fabric was judged on the following three-point scale. ◎: All five individuals are "good," indicating excellent flexibility. ○: One person is "bad," but this can be judged as a satisfactory level of flexibility. △: Two to three people were rated "bad," indicating a slight lack of flexibility. ×: Four or more people are "bad," indicating a lack of flexibility.

[0066] The thermoplastic resins used in the examples and comparative examples are as follows: <Thermoplastic resin 1> Biomass-derived polyethylene terephthalate (abbreviation: BioPET) has an intrinsic viscosity of 0.65, a glass transition temperature of 70°C, and a biomass-derived carbon content of 30%. <Thermoplastic resin 2> This is polyethylene terephthalate (abbreviation: fossil PET) derived from fossil resources, with an intrinsic viscosity of 0.64, a glass transition temperature of 70°C, and a biomass-derived carbon content of 0%. <Thermoplastic resin 3> Density 0.96g / cm 3 Biomass-derived high-density polyethylene (abbreviation: BioPE) has an MFR of 20g / 10min, a melting point of 130℃, and a biomass-derived carbon content of 94%. <Thermoplastic resin 4> Density 0.96g / cm 3 High-density polyethylene derived from fossil resources (abbreviation: fossil PE) has an MFR of 16g / 10min, a melting point of 130℃, and a biomass-derived carbon content of 0%.

[0067] [Examples 1-6, Comparative Examples 1-4] Heat-fusible composite fibers and nonwoven fabrics of the examples and comparative examples were manufactured according to the conditions shown in Tables 1 and 2.

[0068] (Manufacturing of heat-fusible composite fibers) Using the resins shown in Tables 1 and 2, and spinning at a spinning temperature of 305°C, we obtained undrawn fibers with a concentric sheath-core structure, where the first component was located on the core side and the second component on the sheath side. The obtained undrawn fibers were subjected to a drawing process using a drawing machine under the conditions shown in Tables 1 and 2. Afterward, the fibers were crimped to a crimp count of 16 crimps / 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-fusible composite fibers.

[0069] (Non-woven fabric processing) The obtained heat-fusible composite fibers were passed through a roller carding machine to collect a fiber web. A 100cm x 30cm section was cut from the fiber web and heat-treated at a processing temperature of 130°C using a hot air circulation type heat treatment machine to heat-fuse the sheath components and obtain a nonwoven fabric.

[0070] Tables 1 and 2 summarize the manufacturing conditions and physical property evaluation results for each example and comparative example.

[0071] [Table 1]

[0072] [Table 2]

[0073] From the results in Tables 1 and 2, Examples 1 to 6 of the present invention used polyethylene resins with a blending ratio of biomass-derived polyethylene resin to fossil resource-derived polyethylene resin of 20:80 to 90:10. Such heat-fusible composite fibers had a high biomass-derived carbon content, and even with finer fiber counting, the nonwoven fabric maintained its bulkiness and exhibited satisfactory flexibility. In particular, Examples 1 to 3 had very fine composite fibers and exhibited excellent flexibility. On the other hand, the composite fiber of Comparative Example 1 had a high proportion of biomass-derived polyethylene resin, resulting in a low specific volume (low bulk). This is thought to be due to a significant decrease in molecular weight during the resin melting process caused by the high proportion of biomass-derived polyethylene resin, resulting in insufficient stretchability and a decrease in the crystallinity of the polyester resin. Furthermore, lowering the stretching temperature to increase the specific volume (high bulk) resulted in increased fineness and a loss of flexibility (Comparative Example 2). The composite fiber of Comparative Example 3 had a low proportion of biomass-derived polyethylene resin, resulting in slightly inferior bulk and flexibility, making it unsuitable for use as a sanitary material overall. Comparative Example 4, which did not contain biomass-derived resin, achieved acceptable bulk, but was slightly inferior in flexibility, and its low biomass-derived carbon content meant it could not reduce the consumption of fossil resources. [Industrial applicability]

[0074] The heat-fusible composite fiber of the present invention, by blending a polyethylene resin derived from biomass and a polyethylene resin derived from fossil resources in an appropriate ratio as the second component, can provide a nonwoven fabric that reduces the consumption of fossil resources and has excellent bulkiness and flexibility. Therefore, it can be used in a variety of textile products that require reduced consumption of fossil resources, as well as bulkiness and flexibility, such as sanitary materials such as diapers, napkins, or incontinence pads; medical materials such as masks, gowns, or surgical gowns; interior materials such as wall sheets, shoji paper, or flooring materials; lifestyle-related materials such as cover cloths, cleaning wipers, or garbage covers; toiletries such as disposable toilets or toilet covers; pet supplies such as pet sheets, pet diapers, or pet towels; industrial materials such as wiping materials, filters, cushioning materials, oil absorbents, or ink tank absorbents; covering materials, humping materials, bedding materials, and nursing care products.

Claims

1. A heat-fusible composite fiber comprising a polyester resin as the first component and a polyethylene resin having a lower melting point than the first component, The aforementioned polyester resin is polyethylene terephthalate. The polyethylene resin is high-density polyethylene. In the aforementioned polyethylene resin, the blending ratio (by weight) of the biomass-derived polyethylene resin and the fossil resource-derived polyethylene resin is 20:80 to 90:

10. In the aforementioned polyester resin, the blending ratio (by weight) of the biomass-derived polyester resin and the fossil resource-derived polyester resin is 25:75 to 50:

50. The biomass-derived carbon content in the aforementioned biomass-derived polyester resin is 30% or less. The biomass carbon content in the aforementioned heat-fusible composite fiber is 25 to 40%. The fineness of the heat-fusible composite fiber is 2.2 dtex or less. Heat-fusible composite fiber.

2. The heat-fusible composite fiber according to claim 1, wherein the biomass-derived carbon content in the polyethylene resin is 20 to 90%.

3. The heat-fusible composite fiber according to claim 1 or 2, wherein the heat of fusion of the polyester resin in the heat-fusible composite fiber is 24 J / g or more.

4. The heat-fusible composite fiber according to any one of claims 1 to 3, wherein the heat-fusible composite fiber is a sheath-core type heat-fusible composite fiber having the first component as a core component and the second component as a sheath component.

5. A nonwoven fabric comprising the heat-fusible composite fiber described in any one of claims 1 to 4.

6. An absorbent article using heat-fusible composite fibers as described in any one of claims 1 to 4.

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