JP2022160710A - Heat-fusible composite fiber and non-woven fabric using the same - Google Patents

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 The present invention relates to a heat-fusible composite fiber containing a biomass-derived component and a nonwoven fabric obtained using the same.

Conventionally, heat-fusible conjugate fibers, which can be molded by heat-sealing using hot air or heat energy from heating rolls, can be easily obtained into nonwoven fabrics with excellent bulkiness and flexibility. It is widely used for sanitary materials such as napkins and pads, or industrial materials such as daily necessities and filters. In particular, sanitary materials are in direct contact with human skin and need to absorb liquids such as urine and menstrual blood quickly, so bulkiness and flexibility are extremely important. In order to obtain bulkiness, a method of using a highly rigid resin or a method of imparting rigidity by stretching at a high magnification ratio is typical, but in that case, the flexibility of the resulting nonwoven fabric decreases. end up On the other hand, if softness is prioritized, the resulting nonwoven fabric will have lower bulkiness and poorer liquid absorbency.

Therefore, methods have been proposed for obtaining fibers and nonwoven fabrics capable of achieving both bulkiness and flexibility. Patent Document 1 discloses a heat-fusible composite fiber in which the first component is a polyester-based resin and the second component is a polyolefin-based resin having a lower melting point than the first component. , that a bulky and soft nonwoven fabric is obtained.

By the way, in recent years, along with the increasing demand for building a recycling-based society, there is a desire to break away from fossil resources in the material field as well as energy, and the use of biomass-derived materials is attracting attention. Biomass is an organic compound that is photosynthesised from carbon dioxide and water (see, for example, Patent Documents 2 and 3), and if such biomass-derived materials are used as starting materials, it is possible to reduce the amount of fossil resources used. For example, if a biomass-derived material such as polylactic acid is used as a raw material, even if it is incinerated after use and decomposed into carbon dioxide and water, it will be carbon dioxide and water before it is taken in by plants through photosynthesis. Equal to the amount of water, it is possible to build a recycling system or carbon neutral.

Against this background, composite fibers made from biomass-derived materials have been proposed in the field of sanitary materials as well. Patent Document 4 discloses PET and PE conjugate fibers made from biomass-derived substances as raw materials, suppressing the consumption of fossil resources, and obtaining a nonwoven fabric having a uniform texture by polymerizing PE with various polymers. It is stated that

Biomass-derived resins are generally thought to have the same chemical structure as those of conventional fossil resources, so there is no difference in quality. Impurities that could not be removed in the process remain, reducing heat resistance and making it difficult to use as it is in the same way as resins derived from fossil resources. In particular, in the production of nonwoven fabrics for sanitary materials, it is possible to reduce the fineness of fibers in order to obtain good softness and texture. It is difficult to obtain a heat-fusible conjugate fiber with a fineness, and even if a heat-fusible conjugate fiber with a fine fineness is obtained, the nonwoven fabric obtained using the fiber has a very low bulk. end up

JP 2017-214662 A JP 2009-091694 A JP 2008-150759 A JP 2012-140728 A

Thus, in the prior art, it is necessary to use a material derived from only fossil resources in order to obtain a nonwoven fabric that satisfies both bulkiness and flexibility for use as a sanitary material. However, a nonwoven fabric that is both bulky and flexible while suppressing the consumption of fossil resources has not been obtained.

The present invention has been made against the background of the above-mentioned prior art, and its object is to provide a heat-fusible composite fiber that reduces consumption of fossil resources and imparts both bulkiness and flexibility to a nonwoven fabric, and a method for using the same. It is to provide a nonwoven fabric that is

In order to solve the above problems, the inventors have made extensive research. As a result, in the heat-fusible composite fiber in which the first component is a polyester-based resin and the second component is a polyethylene-based resin having a lower melting point than the first component, the biomass-derived polyethylene-based resin is used as the polyethylene-based resin. The present inventors have found that the above problems can be solved by blending a polyethylene-based resin derived from fossil resources in an appropriate ratio, and have completed the present invention.

That is, the present invention is configured as follows.
[1] A heat-fusible conjugate fiber in which the first component is a polyester resin and the second component is a polyethylene resin having a lower melting point than the first component, wherein the polyethylene resin contains biomass-derived A heat-fusible conjugate fiber in which the compounding ratio (weight ratio) of polyethylene-based resin and polyethylene-based resin derived from fossil resources is 20:80 to 90:10.
[2] The heat-fusible composite fiber according to [1], wherein the biomass-derived carbon content in the polyethylene resin is 20 to 90%.
[3] The heat-fusible conjugate fiber according to [1] or [2], wherein the biomass-derived carbon content in the heat-fusible conjugate fiber is 10% or more.
[4] The heat-fusible composite fiber according to any one of [1] to [3], wherein the biomass-derived carbon content in the polyester resin is 30% or less.
[5] The heat-fusible conjugate fiber according to any one of [1] to [4], wherein the heat-fusible conjugate fiber has a fineness of 2.2 dtex or less.
[6] The heat-fusible conjugate fiber according to any one of [1] to [5], wherein the heat of fusion of the polyester resin in the heat-fusible conjugate fiber is 24 J/g or more.
[7] Any one of [1] to [6], wherein the heat-fusible conjugate fiber is a sheath-core heat-fusible conjugate fiber having the first component as a core component and the second component as a sheath component. The heat-fusible composite fiber according to 1.
[8] The heat-fusible conjugate 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 nonwoven fabric comprising the heat-fusible conjugate fiber according to any one of [1] to [8].
[10] An absorbent article using the heat-fusible composite fiber according to any one of [1] to [8].

According to the present invention, it is possible to provide a heat-fusible conjugate fiber that reduces consumption of fossil resources and imparts both bulkiness and flexibility to nonwoven fabrics.

In the heat-fusible composite fiber of the present invention, 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 biomass-derived polyethylene. The compounding ratio (weight ratio) of the base resin and the polyethylene base resin derived from fossil resources is 20:80 to 90:10.

(First component)
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 can be preferably used. In addition to the above aromatic polyester resins, aliphatic polyester resins can also be used, and preferred aliphatic polyester resins include polylactic acid and polybutylene succinate. These polyester-based resins may be not only homopolymers but also copolyesters (copolyesters). At this time, the copolymer components include 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 components such as L-lactic acid. Isomers are available. Examples of such copolymers include polybutylene terephthalate adipate. Furthermore, two or more of these polyester resins may be mixed and used. Among them, an unmodified polymer composed only of polyethylene terephthalate is preferable as the first component in consideration of the raw material cost, the bulkiness of the nonwoven fabric, the thermal stability of the resulting fiber, and the like.

When the polyester-based resin is an aromatic polyester-based resin, it can be obtained, for example, by polycondensation from a diol and a dicarboxylic acid. Dicarboxylic acids used for polycondensation of polyester resins include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid and sebacic acid. Diols that can be used include ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol.

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 to 28%, and further preferably 6 to 24%. preferable. If the biomass-derived carbon content of the polyester resin is 2% or more, it is preferable because the consumption of fossil resources can be reduced. It is preferable because it can impart bulkiness and flexibility to the material.

Here, the biomass-derived carbon content rate is a value obtained by measuring the content of biomass-derived carbon by radioactive carbon ( ¹⁴ C) measurement. Carbon dioxide in the atmosphere contains ¹⁴ C at a certain rate (107 pMC (percent modern carbon)), so plants that grow by taking in carbon dioxide in the atmosphere, such as corn, have a ¹⁴ C content of about 107 pMC. is known to be In addition, ¹⁴ C has a half-life of 5,370 years and returns to nitrogen atoms, and it takes 226,000 years to completely decay. Therefore, fossil fuels such as coal, petroleum, and natural gas, which are thought to have passed more than 226,000 years after carbon dioxide and other substances in the atmosphere were taken in and fixed by plants, mostly contain ¹⁴ C. known not to be included. Therefore, the biomass-derived carbon content can be calculated by measuring the ratio of ¹⁴ C contained in all carbon atoms in the resin. A method for calculating the biomass-derived carbon content rate in the resin in the present invention will be described in detail in Examples below.

The polyester resin is not particularly limited, but containing a biomass-derived polyester resin and a fossil resource-derived polyester resin suppresses the consumption of fossil resources and does not impair the original physical properties of the polyester resin. It is preferable in that it can impart bulkiness and flexibility. From this point of view, the blending ratio (weight ratio) of the biomass-derived polyester resin and the fossil resource-derived polyester resin in the polyester resin is not particularly limited, but it is preferably 5: 95 to 95: 5. , 20:80 to 80:20.

Here, the biomass-derived polyester resin may contain biomass-derived carbon, and preferably has a biomass-derived carbon content of 10% or more, more preferably 20% or more. Such a biomass-derived polyester resin may be a polymer consisting only of a biomass-derived monomer, or a copolymer of a biomass-derived monomer and a fossil resource-derived monomer. When the system resin is an aromatic polyester resin, a copolymer of biomass-derived diol and biomass-derived dicarboxylic acid, a copolymer of biomass-derived diol and fossil resource-derived dicarboxylic acid, and a fossil resource-derived diol Copolymers with biomass-derived dicarboxylic acids can be mentioned. Among them, a copolymer of a biomass-derived diol and a fossil resource-derived dicarboxylic acid is preferable from the viewpoint of availability.

The biomass-derived polyester resin is not particularly limited, and one obtained by a conventionally known method may be used, such as biomass-derived polyethylene terephthalate commercially available from Entobo Co., Ltd., or from Nature Works. Biomass-derived polylactic acid or the like may also be used.

Further, the fossil resource-derived polyester resin means a polyester resin containing no biomass-derived carbon, that is, having a biomass-derived carbon content of 0%. Therefore, the polyester-based resin derived from fossil resources is polymerized only from monomers derived from fossil resources.

The first component is not particularly limited as long as it contains a polyester resin, but preferably contains 80% by mass or more of the polyester resin, more preferably 90% by mass or more of the polyester resin. is that Antioxidants, light stabilizers, ultraviolet absorbers, neutralizers, nucleating agents, epoxy stabilizers, lubricants, antibacterial agents, flame retardants, antistatic agents, and pigments, as long as they do not interfere with the effects of the present invention. Alternatively, an additive such as a plasticizer may be added as appropriate.

(Second component)
The polyethylene-based resin in the present invention is not particularly limited, and is a high-density polyethylene, a linear low-density polyethylene, a low-density polyethylene, or a copolymer of ethylene and other components (eg, α-olefin), or these. However, from the viewpoint of suppressing the phenomenon that the polyethylene resins exposed on the fiber surface are not completely cooled and solidified during spinning and are fused together, it is preferably composed only of high-density polyethylene.

In the polyethylene resin constituting the second component in the present invention, it is important that the compounding ratio (weight ratio) of the biomass-derived polyethylene resin and the fossil resource-derived polyethylene resin is 20:80 to 90:10. be. As in the prior art, when only biomass-derived polyethylene resin is used as the polyethylene resin, if the resin is subjected to a heat history of nearly 300°C in the process of melting, the viscosity and molecular weight of the resin will decrease, and sufficient It is considered that stretchability could not be obtained, and it became difficult to achieve both fineness and rigidity of the conjugate fiber, and it was not possible to obtain a soft and bulky nonwoven fabric. In the present invention, by setting the blending ratio of the biomass-derived polyethylene resin to 90% by weight or less, the viscosity and molecular weight reduction of the polyethylene resin are suppressed, and the extension elongation in the process of forming the composite fiber is moderate. This makes it possible to achieve both fineness and rigidity of the composite fiber, and by setting the blending ratio of the biomass-derived polyethylene resin to 20% by weight or more, the biomass-derived carbon content of the composite fiber is improved and fossilized. It has been found that not only can the consumption of resources be suppressed, but also the softness of the nonwoven fabric can be further improved. From this point of view, the blending ratio (weight ratio) of the biomass-derived polyethylene resin and the fossil resource-derived polyethylene resin is preferably 30:70 to 70:30, and 40:60 to 50:50. is more preferred.

Here, the biomass-derived polyethylene resin may contain biomass-derived carbon, and preferably has a biomass-derived carbon content of 90% or more, more preferably 94% or more. Such a biomass-derived polyethylene resin may be a polymer composed only of biomass-derived monomers or a polymer of a biomass-derived monomer and a fossil resource-derived monomer. ethylene polymers, copolymers of biomass-derived ethylene and biomass-derived α-olefins (propylene, butylene, hexene, octene, etc.), copolymers of biomass-derived ethylene and fossil resource-derived ethylene, biomass copolymers of ethylene derived from fossil resources and α-olefins derived from fossil resources, or copolymers of α-olefins derived from biomass and ethylene derived from fossil resources. Among them, from the viewpoint of suppressing adhesion between fibers when forming composite fibers, the biomass-derived polyethylene resin is a polymer of biomass-derived ethylene or a polymer of biomass-derived ethylene and fossil resource-derived ethylene. is preferred.

The biomass-derived polyethylene resin is not particularly limited, and one obtained by a conventionally known method may be used. For example, bioethanol is obtained by fermenting starch and sugar obtained from corn, sugarcane, sweet potato, etc. with microorganisms. and dehydrating it to produce biomass-derived ethylene, which can be produced by polymerizing it. A biomass-derived polyethylene resin commercially available from Braskem and the like may also be used.

Further, the polyethylene-based resin derived from fossil resources means a polyethylene-based resin that does not contain biomass-derived carbon, that is, has a biomass-derived carbon content of 0%. Therefore, the polyethylene-based resin derived from fossil resources is polymerized only from monomers derived from fossil resources. A copolymer with can be mentioned. Among them, from the viewpoint of suppressing adhesion between fibers during molding of the composite fiber, the polyethylene-based resin derived from fossil resources is preferably a polymer of ethylene derived from fossil resources.

The density of the biomass-derived polyethylene resin is not particularly limited, but can be exemplified from 0.91 to 0.96 g/cm ³ . In addition, the density of the polyethylene resin derived from fossil resources is not particularly limited, but can be exemplified from 0.91 to 0.96 g / cm ³ , and from the viewpoint of expressing moderate crystallinity and imparting rigidity to the composite fiber. , 0.93 to 0.96 g/cm ³ .

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 40 to 50%. More preferred. If the biomass-derived carbon content rate in the polyethylene resin is 20% or more, it is preferable because it not only suppresses the consumption of fossil resources but also imparts flexibility to the nonwoven fabric. It is preferable because a nonwoven fabric can be obtained.

In addition, the melt mass flow rate (hereinafter abbreviated as MFR) of the polyethylene resin that can be suitably used is not particularly limited, but is preferably 10 to 40 g/10 minutes, and preferably 16 to 20 g/10 minutes. is more preferred, and 17 to 19 g/10 minutes is even more preferred. When the MFR of the polyethylene-based resin is 10 g/10 minutes or more, it is preferable because stable runnability can be obtained. is obtained. 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 satisfy the requirements of the present invention. .

The second component is not particularly limited as long as it contains a polyethylene resin, but preferably contains 80% by mass or more of the polyethylene resin, more preferably 90% by mass or more of the polyethylene resin. is that Additives exemplified for the first component may be included as appropriate, as long as the effects of the present invention are not impaired.

(Heat-fusible composite fiber)
As a combination of components constituting the heat-fusible conjugate fiber (hereinafter sometimes referred to as "conjugate fiber") in the present invention, the first component is a polyester resin, and the second component has a melting point higher than that of the first component. It is not particularly limited as long as it is composed of a polyethylene-based resin having a low viscosity, and it can be used by selecting from the above-described first component and second component. Specific first component/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 can be exemplified. A preferred combination among these is polyethylene terephthalate/high-density polyethylene.

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 to 60%, and even more preferably 25 to 40%. If the biomass-derived carbon content rate of the composite fiber is 10% or more, it is preferable because the consumption of fossil resources can be suppressed, and if it is 60% or less, it becomes easy to maintain the original physical properties of the resin, and the nonwoven fabric has bulkiness. It is preferable because it can provide flexibility.

Although the conjugate fiber of the present invention is not particularly limited, it is preferably a sheath-core heat-fusible conjugate fiber having the first component as the core component and the second component as the sheath component. Above all, it is preferable that the second component has a composite form that completely covers the surface of the composite fiber, and a concentric or eccentric sheath-core structure is more preferable. The cross-sectional shape of the conjugate fiber may be round such as circle and ellipse, square such as triangle and square, irregular shape such as star and octalobate, or hollow.

The composition ratio when combining the first component and the second component is not particularly limited, but the first component / second component is preferably 20/80 to 80/20 (weight ratio), and 40 /60 to 70/30 (weight ratio) is more preferable. By setting the composition ratio within such a range, the strength, bulkiness, and processability of the nonwoven fabric tend to be excellent in balance, which is preferable.

Although the fineness of the composite fiber in the present invention is not particularly limited, it is preferably 2.2 dtex or less, more preferably 0.5 to 2.1 dtex, and 1.6 to 1.8 dtex. More preferred. When the fineness of the composite fiber is 2.2 dtex or less, it is possible to obtain satisfactory softness and texture, especially as a nonwoven fabric for sanitary materials.

Although the breaking strength of the composite fiber is not particularly limited, it is preferably 1.0 to 4.0 cN/dtex, and 1.5 to 2.0 cN/dtex for composite fibers used in absorbent articles, for example. More preferably 5 cN/dtex. If the breaking strength of the composite fiber is 1.0 cN/dtex or more, it is possible to obtain a nonwoven fabric with sufficient strength, and if it is 4.0 cN/dtex or less, it is possible to improve the softness and texture of the nonwoven fabric. becomes. Moreover, although the breaking elongation of the conjugate fiber is not particularly limited, it is preferably 30 to 170%, more preferably 50 to 150%, and even more preferably 60 to 120%. When the breaking elongation of the conjugate fiber is 30% or more, it is preferable because the flexibility and texture of the nonwoven fabric can be improved. It is possible to

In addition, the crimping of the composite fiber is not particularly limited, and the presence or absence of crimping, the number of crimps, and the number of crimps are determined in consideration of the web forming method, the specifications of the web forming equipment, the productivity and required physical properties of the nonwoven fabric, and the like. Crimp properties such as modulus, residual crimp rate, and crimp elastic modulus can be appropriately selected. Moreover, the shape of the crimp is not particularly limited, and a zigzag-shaped mechanical crimp, a spiral-shaped or ohmic-shaped three-dimensional crimp, or the like can be appropriately selected. Furthermore, the crimp may be actual or latent in the heat-fusible conjugate fiber.

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, more preferably 26 J/g or more. The heat of fusion of the polyester resin in the composite fiber is considered to be a value that reflects the crystallinity of the polyester resin in the composite fiber. It becomes possible to impart bulkiness and softness to the nonwoven fabric. Moreover, the upper limit of the heat of fusion of the polyester resin in the composite fiber is not particularly limited, but is practically 35 J/g or less.

Although the fiber length of the heat-fusible conjugate fiber in the present invention is not particularly limited, it is preferably 3 mm or more, more preferably 30 to 64 mm. Within such a range, it is possible to easily obtain a web having excellent opening property and texture in a web forming process such as a carding method, and a nonwoven fabric having uniform physical properties can be obtained, which is preferable.

(Method for producing heat-fusible composite fiber)
The method for producing the heat-fusible conjugate fiber of the present invention is not particularly limited, and any known method for producing a heat-fusible conjugate fiber may be employed, but it is possible to achieve high productivity and high yield. As a method for producing the heat-fusible conjugate fiber, the method described later can be exemplified.

(Spinning process)
A polyester-based resin, which is a raw material for the composite fiber of the present invention, is added to the first component, a polyethylene-based resin having a melting point lower than that of the first component is added to the second component, and the first component and the second component are melt-spun. is a combined undrawn fiber.

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 still more preferably 300° C. or higher. If the spinning temperature is 250° C. or higher, the number of broken yarns during spinning can be reduced, and an undrawn yarn that tends to retain elongation after drawing can be obtained, and the fineness can be easily reduced. These effects become more pronounced, and a temperature of 300° C. or higher is even more pronounced, which is preferable. The upper limit of the temperature is not particularly limited as long as it is a temperature at which spinning can be suitably performed.

Although the spinning speed is not particularly limited, it is preferably 300 to 1500 m/min, more preferably 400 to 1000 m/min. A spinning speed of 300 m/min or more is preferable in terms of increasing the single-hole discharge rate when obtaining an undrawn yarn having an arbitrary spinning fineness and obtaining satisfactory productivity.

(Stretching process)
The undrawn fibers obtained under the above conditions are drawn in the drawing step. The stretching 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 the polyester resin. It is 35 to 60°C higher than the glass transition temperature of and 5°C or lower than the melting point of the polyethylene resin.

Here, the drawing temperature means the temperature of the fiber at the drawing start position. If the stretching temperature is "the glass transition temperature of the polyester resin as the first component + 30°C" or higher, the effect can be obtained even if the film is stretched at a high strain rate, that is, at a high magnification, which is preferable. Also, the drawing temperature must be lower than the melting point of the polyethylene resin, which is the second component, to suppress the destabilization of the drawing process due to fusion between fibers. For example, when stretching an undrawn fiber in which polyethylene terephthalate having a glass transition temperature of 70°C is used as the first component and high-density polyethylene having a melting point of 130°C is used as the second component, and the stretching temperature. When the drawing temperature is 100° C. or higher, the amount of heat applied to the fiber increases, and the difference in drawability between the polyester-based resin and the polyethylene-based resin becomes small. As a result, the risk of sheath-core peeling during card processing in the non-woven fabric manufacturing process is reduced.

The draw ratio is not particularly limited, but is preferably 2 to 7 times, more preferably 4 to 6 times. By setting the draw ratio within the above range, the fineness and rigidity of the conjugate fiber are well balanced, and a nonwoven fabric having excellent bulkiness and flexibility can be easily obtained, and furthermore, the conjugate fiber can be obtained with high productivity. becomes possible.

(Crimping process)
The drawn fibers obtained in the drawing step may be mechanically crimped by a crimper or the like. The number of crimps applied in the crimping step is not particularly limited, and is preferably 10 to 25 crimps/2.54 cm. Adjustable.

(Heat treatment process)
The drawn fibers obtained in the drawing step may be heat treated. Heat treatment after stretching increases the crystallinity of the polyester-based resin, which is the first component of the heat-fusible conjugate fiber, and improves the bulkiness of the nonwoven fabric. The heat treatment temperature is not particularly limited, but it is preferable to perform the heat treatment at a temperature higher than 30 to 70° C., which is the glass transition temperature of the polyester resin, and lower than the melting point of the polyethylene resin.

(cutting process)
When the conjugate fiber of the present invention is processed into a non-woven fabric and a carding process is employed, the conjugate fiber must be cut to an arbitrary length in order to pass through a carding machine. The length to cut the conjugate fiber and the cut length are preferably 30 to 64 mm from the viewpoint of fineness and carding machine passing performance.

(Fiber treatment agent application step)
In addition, the conjugate fiber of the present invention may have its surface treated with various fiber treatment agents, thereby imparting functions such as hydrophilicity, water repellency, antistatic properties, surface smoothness, and abrasion resistance. be able to.
Regarding the step of applying the fiber treatment agent, the method of applying the fiber treatment agent to the undrawn fiber by a kiss roll when the undrawn fiber is taken off, or the method of applying the fiber treatment agent during and/or after drawing by a touch roll method, a dipping method, a spraying method, or the like. can be exemplified.

(Nonwoven fabric)
Since the nonwoven fabric of the present invention contains the heat-fusible conjugate fibers described above, it reduces the consumption of fossil resources and is excellent in bulkiness and flexibility.

The biomass-derived carbon content of the nonwoven fabric in the present 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%. It is more preferably 40% or more. In order to obtain such a nonwoven fabric having a biomass-derived carbon content of 10% or more, only conjugate fibers having a biomass-derived carbon content of 10% or more may be used, or mixed with other fibers to obtain a total Alternatively, the biomass-derived carbon content may be 10% or more. Other fibers include, for example, natural fibers (wood fibers, etc.), regenerated fibers (rayon, etc.), semi-synthetic fibers (acetate, etc.), chemical fibers, and synthetic fibers (polyester, acrylic, nylon, vinyl chloride, etc.). It's okay. The mixing ratio of such fibers other than the heat-fusible conjugate fibers is not limited as long as the effects of the present invention are not impaired, but can be, for example, 1 to 50% by weight.

Although the basis weight of the nonwoven fabric is not particularly limited, it is preferably 15 to 40 g/m ² and more preferably 18 to 30 g/m ² when used as a nonwoven fabric for sanitary materials. If the basis weight is 15 g/m ² or more, it is preferable because the texture and cushioning properties can be maintained and liquid return can be suppressed, and if it is 40 g/m ² or less, surface smoothness, air permeability, and liquid permeability It is preferable because it can be held.

Although the specific volume of the nonwoven fabric is not particularly limited, it is preferably 30 to 100 cm ³ /g, more preferably 50 to 70 cm ³ /g, especially when used as a nonwoven fabric for sanitary materials. The specific volume is a parameter used as an index of bulkiness, and it can be evaluated that the larger the specific volume, the bulkier the nonwoven fabric. If the specific volume is ³⁰ cm ³ /g or more, it is possible to obtain a bulkiness that can be applied as a sanitary material. It is preferable because it has excellent workability into sanitary materials.

The longitudinal strength (MD strength) of the nonwoven fabric is not particularly limited, but is preferably 35 N/50 mm or more, more preferably 45 N/50 mm or more. If the MD strength of the nonwoven fabric is 35 N/50 mm or more, it is preferable because it is excellent in workability into sanitary materials.

The nonwoven fabric of the present invention may consist of one type (single-layer) nonwoven fabric, or may be a laminate of two or more types of nonwoven fabrics having different fineness, composition, density, etc. of the conjugate fibers used. When two or more types of nonwoven fabrics are laminated, for example, by laminating nonwoven fabrics with different fineness of conjugate fibers, a nonwoven fabric in which the size of the gap formed between the fibers changes in the thickness direction of the nonwoven fabric is used. It is possible to control the properties, liquid permeation rate, surface texture, etc. Further, for example, by laminating nonwoven fabrics having different conjugate fiber compositions, a nonwoven fabric in which the hydrophilicity and hydrophobicity of the nonwoven fabric change in the thickness direction of the nonwoven fabric can be obtained, and the liquid permeability and the liquid permeability can be controlled.

In addition, the nonwoven fabric of the present invention is not particularly limited, but other nonwoven fabrics such as through-air nonwoven fabrics, airlaid nonwoven fabrics, spunbond nonwoven fabrics, meltblown nonwoven fabrics, spunlace nonwoven fabrics, needle punch nonwoven fabrics, films, meshes, or nets, films, and sheets. may be laminated and integrated with. By laminating and integrating, it is possible to control liquid permeation, liquid permeation speed, liquid return, etc. The method of stacking and integrating is not particularly limited, but examples include a method of stacking and integrating using an adhesive such as hot melt, and a method of stacking and integrating by thermal bonding such as through air or heat embossing.

The nonwoven fabric is subjected to shaping processing, perforation processing, antistatic processing, water repellent processing, hydrophilic processing, antibacterial processing, ultraviolet absorption processing, near infrared absorption processing, electret processing, etc. within the range that does not impair the effects of the present invention. may be applied according to

(Method for manufacturing nonwoven fabric)
The method for producing the nonwoven fabric is not particularly limited, and a method of forming a web containing the heat-fusible conjugate fibers described above and integrating them by heat or entangling can be exemplified.

The method of forming the web is not particularly limited, and even a long fiber web formed by a spunbond method, a meltblown method, a tow opening method, or the like can be carded using short fibers (staples or chops). It may be a short fiber web formed by a method, an airlaid method, a wet method, or the like, but from the viewpoint of imparting bulkiness and flexibility to the nonwoven fabric, a card method or an airlaid method is preferable, and a card method is used. is more preferable. In the present invention, the term "web" refers to a fiber assembly in which fibers are not a little entangled, and means a state in which intersection points of heat-fusible conjugate fibers are not fused.

The method for unifying the web by heat or entangling is not particularly limited, and examples thereof include a through-air method, a heat calendering method, a hydroentangling method, or a needle punching method, but from the viewpoint of imparting bulkiness and flexibility to the nonwoven fabric. Therefore, the through-air method is preferred. As the through-air method, known equipment such as a method of heat-sealing conjugate fibers with each other by means of a heat treatment device (e.g., hot air penetration type heat treatment device, hot air blowing type heat treatment device) equipped with a transport support for supporting and transporting the web, Apply the conditions.

The heat-fusible composite fiber of the present invention can be used, for example, in sanitary materials such as diapers, napkins, or incontinence pads, medical materials such as masks, gowns, or surgical gowns, wall sheets, shoji paper, or flooring materials. Living-related materials such as interior materials, cover cloths, cleaning wipers, or garbage covers, toiletry products such as disposable toilets or toilet covers, pet products such as pet sheets, pet diapers, or pet towels, wiping Industrial materials such as materials, filters, cushioning materials, oil adsorbents, ink tank adsorbents, covering materials, poultice materials, bedding materials, nursing care products, etc. It can be used for a variety of demanding textile applications.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the scope of the present invention is not limited to these.

Evaluation of physical properties in the present invention was carried out by the following methods.
<Biomass-derived carbon content>
Samples were measured for total carbon and ¹⁴ C content using an accelerator mass spectrometer (AMS) (combined tandem accelerator and mass spectrometer). From the total carbon and ¹⁴ C contents in the sample, the biomass-derived carbon content of the carbon contained in the sample was calculated according to the following formula.
Biomass-derived carbon content (%) = (biomass-derived carbon ( ¹⁴ C) amount in sample/total carbon amount in sample) x 100
<Intrinsic viscosity of polyester resin>
Measured according to JIS K 7367-1.
<MFR of polyethylene resin>
The melt mass flow rate (MFR) was measured according to JIS K 7210. It was measured according to condition D (test temperature: 190°C, load: 2.16 kg) in Annex A Table 1.
<Fineness of undrawn fiber, fineness of heat-fusible composite fiber, breaking strength, breaking elongation>
Measured according to JIS-L-1015.
<Heat of fusion of polyester-based resin in heat-fusible conjugate fiber>
Using a differential scanning calorimeter (DSC8500) manufactured by Perkin Elmer Japan, the heat of fusion of the polyester resin in the composite fiber was measured according to the following procedure. First, the composite fiber was cut into pieces having a mass of 4.20-4.80 mg, which was filled in a sample pan and covered. Then, measurements were taken from 30° C. to 300° C. at a rate of temperature increase of 10° C./min in a N ₂ purge to obtain a melting 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.
<Nonwoven fabric basis weight>
Three pieces of nonwoven fabric were cut into squares of 10 cm x 10 cm, each weight was measured, converted to a unit area, and the average value of the obtained values was taken as the basis weight of the nonwoven fabric.
<Bulkiness of nonwoven fabric>
Using a digisickness tester manufactured by Toyo Seiki Co., Ltd., a pressure of 3.5 g/cm ² was applied by an indenter (load) with a diameter of 35 mm, 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 ) x 1000
<MD strength of nonwoven fabric>
A sample with a size of 50 mm × 150 mm and cut long in the longitudinal direction was pulled using an autograph (AGX-J) manufactured by Shimadzu Corporation at a distance between chucks of 100 mm and a tensile speed of 100 mm / min. was used as the MD intensity.
<Flexibility of nonwoven fabric>
A 150mm x 150mm piece of nonwoven fabric was cut out and subjected to a sensory test ("good" or "bad") by five panelists in terms of surface smoothness, cushioning properties, and drape properties. Judged.
⊚: All 5 panelists are "good" and can be judged to have excellent flexibility.
◯: 1 person is “bad” and can be judged to have satisfactory flexibility.
Δ: 2 to 3 people gave “bad”, and it can be judged that the flexibility is slightly inferior.
x: 4 or more persons rated "bad" and can be judged to have poor flexibility.

The thermoplastic resins used in Examples and Comparative Examples are as follows.
<Thermoplastic resin 1>
Biomass-derived polyethylene terephthalate (abbreviation: bio-PET) having an intrinsic viscosity of 0.65, a glass transition point of 70° C., and a biomass-derived carbon content of 30%
<Thermoplastic resin 2>
Fossil resource-derived polyethylene terephthalate (abbreviation: fossil PET) having an intrinsic viscosity of 0.64, a glass transition point of 70 ° C., and a biomass-derived carbon content of 0%
<Thermoplastic resin 3>
Biomass-derived high-density polyethylene (abbreviation: bio-PE) having a density of 0.96 g/cm ³ , an MFR of 20 g/10 min, a melting point of 130° C., and a biomass-derived carbon content of 94%
<Thermoplastic resin 4>
Fossil resource-derived high-density polyethylene (abbreviation: fossil PE) having a density of 0.96 g/cm ³ , an MFR of 16 g/10 min, a melting point of 130° C., and a biomass-derived carbon content of 0%

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

(Manufacturing of heat-fusible composite fiber)
Using the resins shown in Tables 1 and 2, at a spinning temperature of 305 ° C., spinning at the first component / second component ratio (weight ratio) shown in Table 1, the first component on the core side and the second component on the sheath side. An undrawn fiber having a concentric sheath-core structure was obtained.
The obtained undrawn fibers were subjected to a drawing step under the conditions shown in Tables 1 and 2 using a drawing machine. Thereafter, crimping is performed so that the number of crimps is 16 crimps/2.54 cm, heat treatment is performed for 5 minutes at the heat treatment temperature shown in Table 1, and the fiber length is cut to 44 mm. fiber was obtained.

(Nonwoven fabric processing)
The resulting heat-fusible conjugate fiber is passed through a roller card machine to obtain a fiber web, and a 100 cm x 30 cm piece is cut out from the fiber web and heat treated at a processing temperature of 130°C using a hot air circulation type heat treatment machine to remove the sheath component. A nonwoven fabric was obtained by heat-sealing.

Tables 1 and 2 collectively show the production conditions and physical property evaluation results for each example and comparative example.

From the results in Tables 1 and 2, in Examples 1 to 6 according to the present invention, the blending ratio of the polyethylene resin derived from biomass and the polyethylene resin derived from fossil resources is 20: 80 to 90: 10. Such a heat-fusible conjugate fiber has a high biomass-derived carbon content, maintains bulkiness of the nonwoven fabric even when fineness is reduced, and has satisfactory flexibility. In particular, Examples 1 to 3 had a small fineness of the conjugate fiber and were very excellent in flexibility.
On the other hand, the composite fiber of Comparative Example 1 had a high blending ratio of the biomass-derived polyethylene resin and a small specific volume (low bulk). This is because the blending ratio of the biomass-derived polyethylene resin is high, and the molecular weight decreases significantly during the melting process of the resin. It is thought that Further, when the drawing temperature was lowered in order to increase the specific volume (increase the bulk), the fineness increased and the flexibility was impaired (Comparative Example 2). In addition, the composite fiber of Comparative Example 3 had a low blending ratio of the biomass-derived polyethylene resin, resulting in slightly inferior bulkiness and flexibility, and was generally difficult to apply as a sanitary material. Comparative Example 4, which does not contain a biomass-derived resin, has an acceptable bulkiness, but is slightly inferior in flexibility, has a low biomass-derived carbon content, and cannot suppress the consumption of fossil resources. I didn't.

The heat-fusible conjugate fiber of the present invention is obtained by blending biomass-derived polyethylene-based resin and fossil resource-derived polyethylene-based resin in an appropriate ratio as the polyethylene-based resin that constitutes the second component. It is possible to provide a nonwoven fabric with reduced consumption and excellent bulkiness and flexibility. Therefore, 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, cover cloths, cleaning wipers, Or daily life-related materials such as garbage covers, toiletry products such as disposable toilets or toilet covers, pet supplies such as pet sheets, pet diapers, or pet towels, wiping materials, filters, cushion materials, oil adsorbents, Or for industrial materials such as adsorbents for ink tanks, coating materials, poultice materials, bedding materials, nursing care products, and various other textile products that require low consumption of fossil resources and are bulky and flexible. can be used.

Claims (10)

A heat-fusible composite fiber composed of a polyester-based resin as a first component and a polyethylene-based resin having a melting point lower than that of the first component as a second component, wherein the polyethylene-based resin is a polyethylene-based resin derived from biomass. and a polyethylene-based resin derived from fossil resources in a compounding ratio (weight ratio) of 20:80 to 90:10. The heat-fusible composite fiber according to claim 1, wherein the biomass-derived carbon content in the polyethylene resin is 20 to 90%. The heat-fusible conjugate fiber according to claim 1 or 2, wherein the heat-fusible conjugate fiber has a biomass-derived carbon content of 10% or more. The heat-fusible composite fiber according to any one of claims 1 to 3, wherein the polyester-based resin has a biomass-derived carbon content of 30% or less. The heat-fusible conjugate fiber according to any one of claims 1 to 4, wherein the heat-fusible conjugate fiber has a fineness of 2.2 dtex or less. The heat-fusible conjugate fiber according to any one of claims 1 to 5, wherein the heat of fusion of the polyester-based resin in the heat-fusible conjugate fiber is 24 J/g or more. The heat-fusible conjugate fiber according to any one of claims 1 to 6, wherein the heat-fusible conjugate fiber is a sheath-core type heat-fusible conjugate fiber having the first component as a core component and the second component as a sheath component. heat-fusible composite fiber. The heat-fusible conjugate fiber according to any one of claims 1 to 7, wherein the polyester-based resin is polyethylene terephthalate, and the polyethylene-based resin is high-density polyethylene. A nonwoven fabric comprising the heat-fusible conjugate fiber according to any one of claims 1 to 8. An absorbent article using the heat-fusible conjugate fiber according to any one of claims 1 to 8.