JP2018168513A - Thermoplastic resin fiber and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-strength fiber. SOLUTION: The thermoplastic resin fiber of the present invention is formed by dispersing fine cellulose fibers in a fiber-forming thermoplastic resin. The average fiber diameter of the fine cellulose fibers is preferably 0.1 nm or more and 300 nm or less. It is also preferable that the fine cellulose fiber has a structure in which an aliphatic hydrocarbon group having 1 or more carbon atoms and / or an aromatic hydrocarbon group is bonded. It is also preferable that the thermoplastic resin is one or more resins selected from the group consisting of polyolefins and polyesters. [Selection diagram] None

Description

  The present invention relates to a thermoplastic resin fiber and a method for producing the same.

  In recent years, technologies that have a low environmental impact have come to the spotlight. Under such technical background, materials using cellulose fibers, which are biomass that exists naturally in large quantities, have attracted attention. For example, in Non-Patent Documents 1 to 3, acicular fine cellulose fibers called cellulose nanowhiskers are dispersed in an organic solvent such as toluene, cyclohexane, or chloroform to obtain a dispersion. It is described that a composite material of lactic acid and cellulose nanowhiskers is obtained. In the technologies described in these documents, an anionic surfactant such as a phenyl group-containing phosphate ester is allowed to act on cellulose nanowhiskers to hydrophobize cellulose nanowhiskers in an organic solvent of cellulose nanowhiskers. Enables stable dispersion.

  Patent Document 1 describes that a composite material having both high mechanical strength and transparency can be obtained by blending a fine cellulose fiber composite adsorbed with a surfactant into various resins. .

  There is also an attempt to improve the properties of the resin by mixing fine cellulose fibers with a resin to form a resin composition. For example, Patent Document 2 describes an epoxy resin composite composed of finely modified cellulose fibers obtained by treating fine cellulose fibers with an organic onium compound and an epoxy resin. Patent Document 3 describes a wiring board made of a fiber-reinforced composite material containing acetylated fine cellulose fibers and a matrix material made of a synthetic polymer. In Patent Document 4, for the purpose of obtaining a resin composition having a low linear expansion coefficient and high transparency, an organic fiber comprising a fine cellulose fiber having a diameter of 4 to 1000 nm and an organic cationic compound is hydrophobic. It is described that it is contained in a functional resin.

JP 2011-140738 A JP 2010-59304 A JP 2011-1559 A JP 2011-47084 A

L. Heux, et al. Langmuir, 16 (21), 2000. C. Bonini, et al. , Langmuir, 18 (8), 2002. L. Petersson, et al. , Composites Science and Technology, 67, 2007.

  As described above, the fine cellulose fiber is used in combination with various materials and is used to enhance the function of the material, but the fine cellulose fiber is used in combination with a fiber-forming thermoplastic resin, No consideration has been given to enhancing functionality.

  Accordingly, an object of the present invention is to provide a fiber having various functions improved more than before and a fiber product including the fiber. Moreover, the subject of this invention is providing the suitable manufacturing method of such a fiber and a textile product.

  The present invention solves the above-mentioned problems by providing a thermoplastic resin fiber in which fine cellulose fibers are dispersed in a fiber-forming thermoplastic resin.

  Moreover, this invention provides the nonwoven fabric containing the said thermoplastic resin fiber.

Furthermore, the present invention provides a method for producing the thermoplastic resin fiber as described above.
The present invention provides a method for producing a thermoplastic resin fiber having a step of melt spinning a thermoplastic resin composition containing fine cellulose fibers and a fiber-forming thermoplastic resin.

  According to the present invention, a high-strength fiber and a high-strength nonwoven fabric are provided. Moreover, according to the present invention, there is provided a method in which yarn breakage hardly occurs during melt spinning and a thin fiber can be easily produced.

  Hereinafter, the present invention will be described based on preferred embodiments thereof. The present invention relates to thermoplastic resin fibers. The thermoplastic resin fiber of the present invention is one in which fine cellulose fibers are dispersed in a fiber-forming thermoplastic resin. The thermoplastic resin fiber of the present invention may be in any form of staple fiber and continuous filament depending on the production method and specific application. When the fiber of the present invention is a staple fiber, the fiber length can be, for example, 2 mm or more and 100 mm or less. Whether the fibers of the present invention are in the form of continuous filaments such as staple fibers, spunbond fibers, or meltblown fibers, the thickness should be set appropriately according to the fiber manufacturing method and specific application. Can do.

  Specifically, in the case of a meltblown fiber, the average fiber diameter of the fiber of the present invention is preferably 1500 nm or less, more preferably 1000 nm or less, and even more preferably 750 nm or less. In the case of a melt blown fiber, the average fiber diameter of the fiber of the present invention is preferably 150 nm or more, more preferably 250 nm or more, and further preferably 350 nm or more. In the case of a meltblown fiber, the average fiber diameter of the fiber of the present invention is preferably 150 nm to 1500 nm, more preferably 250 nm to 1000 nm, and further preferably 350 nm to 750 nm.

  In the case of a spunbond fiber, the average fiber diameter of the fiber of the present invention is preferably 70 μm or less, more preferably 45 μm or less, and even more preferably 20 μm or less. In the case of a spunbond fiber, the average fiber diameter of the fiber of the present invention is preferably 5 μm or more, more preferably 7.5 μm or more, and even more preferably 10 μm or more. In the case of a spunbond fiber, the average fiber diameter of the fiber of the present invention is preferably 5 μm or more and 70 μm or less, more preferably 7.5 μm or more and 45 μm or less, and further preferably 10 μm or more and 20 μm or less.

  In the case of staple fibers, the average fiber diameter of the fibers of the present invention is preferably 70 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. In the case of staple fibers, the average fiber diameter of the fibers of the present invention is preferably 5 μm or more, more preferably 8 μm or more, and even more preferably 11 μm or more. In the case of staple fibers, the average fiber diameter of the fibers of the present invention is preferably 5 μm or more and 70 μm or less, more preferably 8 μm or more and 50 μm or less, and even more preferably 11 μm or more and 30 μm or less.

  The thickness of the fiber is generally the same at any position when viewed along the length direction of the fiber, but depending on the fiber manufacturing method and the specific use of the fiber, the length direction The thickness along the line may change regularly or irregularly.

  When the fiber of the present invention is in a fiber state that is not used for a nonwoven fabric, the average fiber diameter is obtained by measuring the fiber diameter of 300 fibers and calculating the average value. When the fiber of the present invention is in the form of a nonwoven fabric, first, five small sample samples are randomly collected from the nonwoven fabric. Next, an enlarged photograph is taken with a scanning electron microscope or the like so that about 20 to 60 fibers are reflected in the field of view. Then, for each photograph, all the fibers in the field of view are measured once, that is, the fiber diameter is measured so as to count about 100 to 300 in total, and the average value is calculated.

  The thermoplastic resin fiber of the present invention may be a single fiber mainly composed of a single resin or a blend of two or more resins, or a composite fiber such as a core-sheath type or a side-by-side type. May be. The cross section of the fiber is generally circular or substantially circular, but depending on the method of manufacturing the fiber and the specific use of the fiber, it may be a deformed fiber having a cross section other than circular.

  The thermoplastic resin fiber of the present invention may be a non-crimped fiber or a crimped fiber depending on the fiber production method and the specific use of the fiber. Alternatively, it may be a non-crimped fiber in a state before use, and a fiber in which crimp is expressed by an external factor before or during use, that is, a latently crimped fiber. As an external factor, for example, application of heat can be cited. When the thermoplastic resin fiber of the present invention is crimped, the number of crimps (JIS L0208) is preferably set to, for example, 9 pieces / 25 mm or more and 30 pieces / 25 mm or less according to the specific use of the fiber. .

  The thermoplastic resin fiber of the present invention may be a heat-shrinkable fiber whose length is shortened by application of heat, or may be a heat-extensible fiber whose length is increased by application of heat.

  The thermoplastic resin fiber of the present invention contains a fiber-forming thermoplastic resin. As the fiber-forming thermoplastic resin, those similar to those conventionally used in the technical field can be used without particular limitation. For example, polyolefin, polyester, polyamide, polyacrylonitrile, polyphenylene sulfide, polyether ether ketone and the like can be mentioned. Examples of the polyolefin include polyethylene, polypropylene, and an ethylene-α-olefin copolymer. Examples of the polyester include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, wholly aromatic polyester, and polylactic acid. Examples of polyamide include nylon 6 and nylon 66. These resins may be used alone or in combination of two or more. Among these resins, it is particularly preferable to use one or more resins selected from the group consisting of polyolefins and polyesters from the viewpoint of suitability for melt spinning in which fine cellulose fibers are dispersed. In particular, it is preferable to use a polypropylene resin because it is particularly excellent in suitability for melt spinning in which fine cellulose fibers are dispersed. The type of the thermoplastic resin can be confirmed by analyzing it by a known means such as differential scanning calorimetry measurement or solid nuclear magnetic resonance measurement.

  The thermoplastic resin fiber of the present invention has a fiber-forming thermoplastic resin as a matrix, and fine cellulose fibers as a dispersed phase are dispersed in the matrix. When observing an arbitrary cross section of the thermoplastic resin fiber of the present invention, the fine cellulose fiber is preferably in a dispersed state so as to be observed with almost the same probability in any cross section. In other words, the fine cellulose fibers are preferably uniformly dispersed in the fiber-forming thermoplastic resin matrix.

As a result of the inventor's investigation, it has been found that the strength of the fiber, for example, the tensile strength is improved by dispersing the fine cellulose fiber in the fiber-forming thermoplastic resin. It is preferable that the tensile strength of the fiber is improved since it is difficult to cut the fiber when the fiber is processed to produce a fiber product. From the viewpoint of making such advantageous effects even more remarkable, the content of fine cellulose fibers in the thermoplastic resin fiber of the present invention is preferably 0.01% by mass or more, and 0.05% by mass or more. More preferably, it is more preferably 0.1% by mass or more. Further, it is preferably 50% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less. Specifically, the content of fine cellulose fibers in the thermoplastic resin fiber of the present invention is preferably 0.01% by mass or more and 50% by mass or less, and 0.05% by mass or more and 10% by mass or less. Is more preferable, and more preferably 0.1% by mass or more and 5% by mass or less.
When the content of the fine cellulose fiber in the thermoplastic resin fiber is equal to or higher than the lower limit, the effect due to the inclusion of the fine cellulose fiber can be successfully obtained, and when the content is equal to or lower than the upper limit, the fiber can be easily spun. .
The content of the fine cellulose fiber in the thermoplastic resin fiber can be confirmed by analyzing by a known means such as differential scanning calorimetry measurement or solid nuclear magnetic resonance measurement. For example, the content of a thermoplastic resin is analyzed by differential scanning calorimetry, and the content of fine cellulose fibers is calculated based on the difference between them, or the thermoplastic resin and cellulose-derived materials measured by solid nuclear magnetic resonance method are used. This can be done from the ratio to the signal.

  From the same viewpoint as described above, the content of the fiber-forming thermoplastic resin in the thermoplastic resin fiber of the present invention is preferably 50% by mass or more, more preferably 90% by mass or more, and 95% by mass. % Or more is more preferable. Moreover, it is preferable that it is 99.99 mass% or less, it is more preferable that it is 99.95 mass% or less, and it is still more preferable that it is 99.9 mass% or less. Specifically, the content of the fiber-forming thermoplastic resin in the thermoplastic resin fiber of the present invention is preferably 50% by mass or more and 99.99% by mass or less, and 90% by mass or more and 99.95% by mass. More preferably, it is 95 mass% or more and 99.9 mass% or less.

  The fine cellulose fiber contained in the thermoplastic resin fiber of the present invention has a fine average fiber diameter of preferably 300 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less. There is no restriction | limiting in particular in the lower limit of the average fiber diameter of a fine cellulose fiber, and it is so preferable that it is thin, for example, it is preferable that it is a thin diameter about 0.1 nm from a viewpoint which expresses the effect of this invention notably. Specifically, the average fiber diameter of the fine cellulose fibers is preferably from 0.1 nm to 300 nm, more preferably from 0.1 nm to 100 nm, and even more preferably from 0.1 nm to 50 nm. . The fiber diameter of the fine cellulose fiber is measured by the following measuring method.

<Measurement method of fiber diameter>
For the fine cellulose fiber used as a raw material, an aqueous dispersion of fine cellulose fiber having a solid content concentration of 0.0001% by mass was prepared, and the dispersion was dropped on mica (mica) and dried to be an observation sample. Using an atomic force microscope (NanoNaViII, SPA400, manufactured by Hitachi High-Tech Science Co., Ltd., the probe uses SI-DF40Al manufactured by the same company), the fiber height of the fine cellulose fibers in the observed sample is measured. And in the microscope image which can confirm a fine cellulose fiber, five or more fine cellulose fibers are extracted, and an average fiber diameter is computed from those fiber heights. In general, the smallest unit of fine cellulose fibers prepared from higher plants is packed in a square shape with 6 x 6 molecular chains, so the height that can be analyzed with an atomic force microscope image is the width of the fiber. Can be considered.
For the fine cellulose fibers dispersed in the thermoplastic resin fibers, cut out a section of the thermoplastic resin fibers and extract five or more fine cellulose fibers in the section by a known method such as a transmission microscope or an atomic force microscope. Measure and calculate the average fiber diameter.

  In addition to the fine cellulose fibers, the fine cellulose fibers preferably have a cellulose carboxyl group content within a predetermined range. Specifically, the carboxyl group content of the cellulose constituting the fine cellulose fiber is preferably 0.1 mmol / g or more, more preferably 0.4 mmol / g or more, particularly preferably 0.6 mmol / g or more, And it is preferably 3 mmol / g or less, more preferably 2 mmol / g or less, and particularly preferably 1.8 mmol / g or less. More specifically, it is preferably 0.1 mmol / g or more and 3 mmol / g or less, more preferably 0.4 mmol / g or more and 2 mmol / g or less, and particularly preferably 0.6 mmol / g or more and 1.8 mmol / g or less. . The carboxyl group content of the fine cellulose fiber is measured by the following measuring method.

<Measurement method of carboxyl group content>
Take a dry cellulose 0.5g fine cellulose fiber in a 100mL beaker, add deionized water to make a total of 55mL, add 5M 0.01M sodium chloride solution to prepare a dispersion, and fine cellulose fiber is fully dispersed The dispersion is stirred until 0.1M hydrochloric acid is added to this dispersion to adjust the pH to 2.5-3, and an automatic titrator (AUT-50, manufactured by Toa DKK Corporation) is used to add a 0.05M sodium hydroxide aqueous solution to a waiting time of 60. The solution is dropped into the dispersion under the condition of seconds, and the conductivity and pH values are measured every minute. Measurement is continued until pH 11 is obtained to obtain a conductivity curve. From this conductivity curve, the sodium hydroxide titration amount is obtained, and the carboxyl group content of the fine cellulose fiber is calculated by the following formula.
Carboxyl group content (mmol / g) = sodium hydroxide titration × sodium hydroxide aqueous solution concentration (0.05 M) / mass of fine cellulose fiber (0.5 g)

The average aspect ratio (fiber length / fiber diameter) of the fine cellulose fibers is preferably 10 or more, more preferably 20 or more, still more preferably 50 or more, and still more preferably 100 or more. Further, it is preferably 1000 or less, more preferably 500 or less, still more preferably 400 or less, and still more preferably 350 or less. The average aspect ratio is, for example, preferably 10 or more and 1000 or less, more preferably 20 or more and 500 or less, still more preferably 50 or more and 400 or less, and still more preferably 100 or more and 350 or less. When fine cellulose fibers having an average aspect ratio in this range are blended with a fiber-forming thermoplastic resin, fibers having excellent dispersibility in the resin and high mechanical strength can be obtained.
For the fine cellulose fibers used as a raw material, the average aspect ratio is determined from the relationship between the concentration of fine cellulose fibers in the dispersion and the specific viscosity of the dispersion with respect to water using the following formula (1). Is calculated in reverse. The following formula (1) is obtained from the viscosity formula (8.138) of the rigid rod-like molecule described in The Theory of Polymer Dynamics, M. DOI and DF EDWARDS, CLARENDON PRESS, OXFORD, 1986, P312 and Lb ² × ρ = M / relationship _{N a} (where, L is the fiber length, b is the fiber width (the fine cellulose fiber cross section is a square), [rho is the fine cellulose fiber concentration (kg ^{/ m} 3), ^M is the molecular weight, _{N a} Represents the Avogadro number.) In the viscosity formula (8.138), the rigid rod-like molecule is a fine cellulose fiber. In the following formula (1), η _sp is the specific viscosity, π is the circumference ratio, ln is the natural logarithm, P is the aspect ratio (L / b), γ = 0.8, ρ _s is the density of the dispersion medium (kg / m ³ ), ρ ₀ represents the density of the cellulose crystals (kg / m ³ ), and C represents the mass concentration of the cellulose (C = ρ / ρ _s ). The average aspect ratio measured by the above measuring method is that of “fine cellulose fiber” to which a structure formed by bonding an aliphatic hydrocarbon group having 1 or more carbon atoms and / or an aromatic hydrocarbon group is not added. However, it is substantially the same as the “fine cellulose fiber composite” described later. Therefore, when the measurement of the aspect ratio of the fine cellulose fiber composite is not easy, the aspect ratio of the fine cellulose fiber may be measured instead of the measurement.

  Regarding the aspect ratio of the fine cellulose fiber dispersed in the thermoplastic resin fiber, a section of the thermoplastic resin fiber is cut out, and the fine cellulose fiber in the section is removed by a known method such as a transmission microscope or an atomic force microscope. The average aspect ratio is calculated by extracting more than one and measuring their fiber length and fiber diameter.

  Fine cellulose fiber can be used in the state of the dispersion liquid, for example. Or it can also be used in the state of the dried material which dried this dispersion liquid as it is. The dried product may be pulverized by mechanical processing. Further, an aqueous dispersion of fine cellulose fibers may be mixed with a non-aqueous solvent such as alcohol to aggregate the fine cellulose fibers, and the aggregate may be used in a dried state.

  The fine cellulose fiber used in the present invention is a fine cellulose fiber composite having a structure formed by bonding an aliphatic hydrocarbon group having 1 or more carbon atoms and / or an aromatic hydrocarbon group. It is preferable from the viewpoint that hydrophobicity can be imparted. Among these, from the viewpoint of achieving both dispersibility in a thermoplastic resin and suitability for the production process of a fine cellulose composite, it is more preferable to have a structure in which an aliphatic hydrocarbon group is bonded. Unless otherwise indicated, the term “fine cellulose fiber” in the present specification does not add a structure in which an aliphatic hydrocarbon group and / or an aromatic hydrocarbon group having 1 or more carbon atoms are bonded. “Fine cellulose fiber” and “fine cellulose fiber composite” in which a structure formed by bonding an aliphatic hydrocarbon group and / or an aromatic hydrocarbon group having 1 or more carbon atoms to “fine cellulose fiber” is added. It is a concept.

  When hydrophobicity is imparted to the fine cellulose fibers, the fine cellulose fibers are more easily dispersed in the fiber-forming thermoplastic resin, and the strength of the fibers is further improved. In this respect, the aliphatic hydrocarbon group preferably has 2 or more carbon atoms, more preferably 3 or more. Moreover, the upper limit of the number of carbon atoms of the aliphatic hydrocarbon group is preferably 30 or less, and more preferably 20 or less, from the viewpoint of suitability for the fine cellulose composite production process. Specifically, the aliphatic hydrocarbon group preferably has 1 to 30 carbon atoms, more preferably 2 to 30 carbon atoms, and even more preferably 3 to 20 carbon atoms. Regarding the aromatic hydrocarbon group, a group having a substituted or unsubstituted aromatic ring is preferably used, and the number of carbon atoms thereof is preferably 8 or more, and more preferably 9 or more. The upper limit of the number of carbon atoms of the aromatic hydrocarbon group is preferably 36 or less, and more preferably 26 or less. Specifically, the carbon number of the aromatic hydrocarbon group is preferably 1 or more and 36 or less, more preferably 8 or more and 36 or less, and still more preferably 9 or more and 26 or less.

  In particular, the fine cellulose fiber has a structure in which an aliphatic hydrocarbon group having 1 or more carbon atoms and / or an aromatic hydrocarbon group is connected to the cellulose main chain of the fine cellulose fiber via an amide bond. A composite is preferable from the viewpoint of further increasing hydrophobicity. In addition, when introducing an aliphatic hydrocarbon group having 1 or more carbon atoms and / or an aromatic hydrocarbon group, the heat resistance of the fine cellulose fiber is improved by using an amide bond, and it can sufficiently withstand kneading at a high temperature. And dispersibility in the resin is improved.

Among aliphatic hydrocarbon groups having 1 or more carbon atoms and / or aromatic hydrocarbon groups bonded via an amide bond, examples of the aliphatic hydrocarbon group include saturated or unsaturated groups having 1 to 30 carbon atoms. A linear or branched hydrocarbon group is mentioned. Specific examples include the following hydrocarbon groups.
-A hydrocarbon group having 1 carbon atom: a methyl group.
-C2-C30 saturated, linear hydrocarbon group: ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, nonyl group, decyl group, dodecyl group, octadecyl group, docosyl group An octacosanyl group.
-Unsaturated, linear hydrocarbon group having 2 to 30 carbon atoms: oleyl group, myristol group, palmitoleyl group, linoleyl group, linolenyl group, eicosanyl group.
A saturated branched hydrocarbon group having 2 to 30 carbon atoms: isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, t-pentyl group, isohexyl group, 2-hexyl group , Dimethylbutyl group, ethylbutyl group.

In addition to the saturated or unsaturated linear or branched hydrocarbon group, an alicyclic hydrocarbon group such as a cyclopentyl group and a cyclohexyl group can be used.
Examples of the aromatic hydrocarbon group having 1 or more carbon atoms include aromatic hydrocarbon groups such as a benzyl group and a phenyl group.

  Further, in addition to the hydrocarbon group, a hydrocarbon group having a hydrophilic group such as hydroxyethyl group and hydroxypropyl group, a polyether chain such as ethylene glycol and propylene glycol, and a hydrocarbon chain having a polyester chain such as lactide and caprolactone. The group is also suitably used as an aliphatic hydrocarbon group having 1 or more carbon atoms and / or an aromatic hydrocarbon group bonded via an amide bond in the fine cellulose fiber used in the present invention.

The average bonding amount of hydrocarbon groups in the fine cellulose fiber composite (average bonding amount per unit mass of the fine cellulose fiber) is preferably 0.1 mmol / g or more, more preferably 0.5 mmol / g or more, and Preferably it is 3 mmol / g or less, More preferably, it is 2 mmol / g or less, Most preferably, it is 1 mmol / g or less. More specifically, it is preferably 0.1 mmol / g or more and 3 mmol / g or less, more preferably 0.1 mmol / g or more and 2 mmol / g or less, and particularly preferably 0.5 mmol / g or more and 1 mmol / g or less. The average bond amount of the hydrocarbon group is calculated by the following formula. In the following formula, “carboxyl group content of fine cellulose fiber before introduction of hydrocarbon group” is measured by the above <Method for measuring carboxyl group content of fine cellulose fiber>, and “fine cellulose fiber after introduction of hydrocarbon group” The “carboxyl group content of the composite” is measured according to <Measurement method of carboxyl group content of fine cellulose fiber composite> described later.
Bond amount of hydrocarbon group (mmol / g) = carboxyl group content of fine cellulose fiber before introduction of hydrocarbon group (mmol / g) −carboxyl group content of fine cellulose fiber composite after introduction of hydrocarbon group (mmol) / G)

  As described above, the fine cellulose fiber composite preferably has an aliphatic hydrocarbon group having 1 or more carbon atoms and / or an aromatic hydrocarbon group introduced through an amide group. More preferably, an aliphatic hydrocarbon group having 1 or more carbon atoms and / or an aromatic hydrocarbon group is introduced by amidating the carboxyl group of the fiber. In this case, all of the carboxyl groups in the fine cellulose fiber composite may be amidated, or the carboxyl groups may remain without being amidated. Further, the carboxyl group may remain in a state of being primary or tertiary amine chloride or quaternary ammonium chloride. The carboxyl group content of the fine cellulose fiber composite used in the present invention is preferably 0 mmol / g or more, more preferably 0.2 mmol / g or more, and preferably 2.9 mmol / g or less, more preferably 1 mmol / g. Hereinafter, it is particularly preferably 0.8 mmol / g or less. More specifically, it is preferably 0 mmol / g or more and 2.9 mmol / g or less, more preferably 0 mmol / g or more and 1 mmol / g or less, and particularly preferably 0.2 mmol / g or more and 0.8 mmol / g or less. The carboxyl group content of the fine cellulose fiber composite is measured as follows.

<Measuring method of carboxyl group content of fine cellulose fiber composite>
Take a fine cellulose fiber composite with a dry mass of 0.5 g in a 100 mL beaker, add deionized water or a mixed solvent of methanol / water = 2/1 to make a total of 55 mL, and add 5 mL of 0.01M sodium chloride aqueous solution to it. In addition, a dispersion is prepared, and the dispersion is stirred until the fine cellulose fiber composite is sufficiently dispersed. To this dispersion, 0.1M hydrochloric acid was added to adjust the pH to 2.5-3, and 0.05M sodium hydroxide aqueous solution was used using an automatic titrator (trade name “AUT-50” manufactured by Toa DKK Corporation). Is dropped into the dispersion under the condition of a waiting time of 60 seconds, and the electric conductivity and pH value are measured every minute, and the measurement is continued until the pH reaches 11, thereby obtaining an electric conductivity curve. From this conductivity curve, the sodium hydroxide titration amount is obtained, and the carboxyl group content of the fine cellulose fiber composite is calculated by the following equation.
Carboxyl group content of fine cellulose fiber composite (mmol / g) = sodium hydroxide titration × sodium hydroxide aqueous solution concentration (0.05 M) / mass of fine cellulose fiber composite (0.5 g)

  As described above, the fine cellulose fiber composite used in the present invention preferably has an aliphatic hydrocarbon group and / or an aromatic hydrocarbon group having 1 or more carbon atoms introduced through an amide group. A primary or secondary amine compound having an aliphatic hydrocarbon group and / or an aromatic hydrocarbon group having 1 or more carbon atoms in the fiber (hereinafter, these are also collectively referred to as “amine compound”). More preferably, an aliphatic hydrocarbon group having 1 or more carbon atoms and / or an aromatic hydrocarbon group is introduced by bonding via an amide bond.

  The fine cellulose fiber can be obtained, for example, by a production method including an oxidation reaction step of obtaining a reaction product fiber by oxidizing natural cellulose fiber, and a refinement step of making the reaction product fiber fine. Specifically, fine cellulose fibers can be obtained by oxidizing natural cellulose fibers in the presence of an N-oxyl compound. The amine compound described above is bonded to the main chain of the fine cellulose fiber thus obtained through an amide bond. The amine compound to be used constitutes a hydrocarbon group bonded through an amide bond in the fine cellulose fiber composite which is a production object.

  Examples of the primary amine include monoalkylamines such as methylamine, ethylamine, propylamine, isopropylamine, butylamine, hexylamine, octylamine, decylamine, dodecylamine, octadecylamine, and oleylamine. Examples of the secondary amine include dialkylamines such as dimethylamine, diethylamine, dibutylamine, and dioctadecylamine.

  In the amidation reaction between an amine compound and fine cellulose fibers, the temperature of the reaction system (reaction temperature of the amidation reaction) is preferably 20 ° C. or higher and 80 ° C. or lower, and the reaction time is preferably 1 hour or longer and 24 hours or shorter. is there. After completion of the amidation reaction, the reaction system is washed and filtered according to a conventional method to remove impurities such as unreacted substances and various by-products. In this way, a fine cellulose fiber composite in which hydrocarbon groups are bonded to fine cellulose fibers via amide bonds is obtained. The fine cellulose fiber composite may be a swollen gel impregnated with a solvent (for example, acetone) used at the time of washing, or may be a dried fiber or powder.

  As long as the raw material can be melt-spun, the thermoplastic resin fiber of the present invention may contain a resin other than the resin of the fiber-forming thermoplastic resin and a substance other than the fine cellulose fiber. Examples of such resins and substances include crystal nucleating agents, antibacterial agents, fungicides, flame retardants, light stabilizers, hydrophilic agents, water repellents, pigments and the like.

  The thermoplastic resin fiber of the present invention is preferably produced by melt spinning a thermoplastic resin composition containing fine cellulose fibers and a fiber-forming thermoplastic resin. For melt spinning, for example, a master batch made of a thermoplastic resin composition containing fine cellulose fibers and a fiber-forming thermoplastic resin is manufactured, and the master batch is supplied to an extruder and melt-kneaded. The melted resin composition is extruded from the spinneret attached to, and is taken up and wound up. You may perform extending | stretching operation after taking over. Or you may perform extending | stretching operation during the taking-up operation of the molten resin extruded from the spinneret by the high-speed melt spinning of the winding speed of 1000 m / min or more.

  In order to produce a thermoplastic resin composition containing fine cellulose fibers and a fiber-forming thermoplastic resin, for example, when the fine cellulose fibers are powder, a mixture of the fine cellulose fibers and the fiber-forming thermoplastic resin is extruded. The mixture may be supplied to a machine, melted and kneaded, and the molten mixture may be extruded into a strand shape, which is cut into a master batch made of pellets. When the fine cellulose fibers are in a dispersion state, the dispersion liquid and the fiber-forming thermoplastic resin are supplied to an explosion-proof extruder and melt-kneaded while volatilizing the dispersion medium. What is necessary is just to extrude in the shape of a strand, cut | judge this, and you may make it the masterbatch consisting of a pellet. In any case, as the extruder, known apparatuses such as a single-screw kneading extruder, a twin-screw kneading extruder, and a pressure kneader can be used.

  Melt spinning is performed using the master batch thus obtained. There are no particular limitations on the melt spinning conditions, and appropriate conditions are employed depending on the type of resin and the like. According to this production method, the fine cellulose fibers are oriented by mixing the fine cellulose fibers with the thermoplastic resin and melt spinning, and the strength of the yarn being spun increases due to the filler effect. Increasing the strength of the yarn being spun is advantageous because it can effectively prevent breakage during melt spinning. Prevention of yarn breakage is desirable from the viewpoint of high-speed melt spinning and spinning of small-diameter fibers. In addition, it is desirable to prevent yarn breakage from the viewpoint that fibers having a uniform fiber diameter can be spun. The possibility of high-speed melt spinning is advantageous from the viewpoint of spinning high-strength fibers resulting from a high draw ratio and spinning productivity.

  In the present invention, the fiber obtained by the melt spinning described above may be subjected to a known post-process as necessary, for example, an oil treatment process or a stretching process, and then cut into a predetermined length to obtain a staple fiber. it can. Various fiber products, for example, non-woven fabrics can be produced using the staple fibers. Examples of the nonwoven fabric using staple fibers include air-through nonwoven fabric. In this nonwoven fabric, the strength of the constituent fibers is improved for the reasons described above, and as a result, the strength of the air-through nonwoven fabric using the fibers as a raw material is also improved.

  Another example of the nonwoven fabric is a spunbond nonwoven fabric. The spunbond method is a method for producing a high-strength long-fiber nonwoven fabric by drawing the melt-spun fiber by air soccer to promote fiber orientation. There is a need for smaller diameters. However, in the prior art, if the drawing force is increased beyond a certain level, there is a problem that the fiber cannot withstand the spinning tension and the yarn breaks. On the other hand, according to the present invention, the strength of the yarn is increased by dispersing the fine cellulose fibers in the thermoplastic resin, and even if the pressure of the air soccer is further increased, the fibers can be stretched without causing yarn breakage. As a result, it becomes possible to produce fine fibers that were impossible in the past, and it is possible to reduce the basis weight and improve the texture of the spunbonded nonwoven fabric.

  Another example of the nonwoven fabric is a melt blown nonwoven fabric. The melt blown method is a method for producing fine fibers by blowing hot air at a high temperature and high speed to a molten resin, and there is a demand for further fine fibers. However, in the prior art, there is a problem that even if an attempt is made to reduce the fiber diameter by increasing the amount of hot air blown to the molten resin to promote stretching, the fiber is cut and the fiber becomes thicker. On the other hand, since the strength of the yarn during spinning is increased by dispersing the fine cellulose fiber in the thermoplastic resin, the fiber can be further stretched without causing yarn breakage even if the amount of hot air is increased. As a result, it becomes possible to produce fine fibers that were impossible in the past. In particular, since conventional melt blown nonwoven fabrics have low strength, for example, they were often used as laminates laminated with other nonwoven fabrics such as spunbond nonwoven fabrics, but the melt blown nonwoven fabrics containing the fibers of the present invention alone have sufficient strength. It can be secured.

  As described above, the nonwoven fabric containing the thermoplastic resin fiber of the present invention has high strength, and therefore, high-speed conveyance in a subsequent process becomes possible. In addition, the life, friction resistance and pressure resistance when using the nonwoven fabric as a filter are improved. Further, the non-woven fabric has a good touch feeling. Therefore, such a nonwoven fabric is useful as, for example, a filter, a top sheet or a back sheet of an absorbent article, and a cleaning sheet.

  As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, in the said embodiment, although the air through nonwoven fabric, the spun bond nonwoven fabric, and the melt blown nonwoven fabric were mentioned as an example of the nonwoven fabric containing the thermoplastic resin fiber of this invention, the thermoplastic resin fiber of this invention is used for the other nonwoven fabric. Also good.

In relation to the above-described embodiment, the present invention further discloses the following thermoplastic resin fiber and a method for producing the same.
<1>
A thermoplastic resin fiber in which fine cellulose fibers are dispersed in a fiber-forming thermoplastic resin.

<2>
The thermoplastic resin fiber according to <1>, wherein the thermoplastic resin fiber has the thermoplastic resin as a matrix, and fine cellulose fibers as a dispersion layer are dispersed in the matrix.
<3>
The average fiber diameter of the fine cellulose fibers is from 0.1 nm to 300 nm, preferably from 0.1 nm to 100 nm, more preferably from 0.1 nm to 50 nm, described in <1> or <2>. Thermoplastic resin fiber.
<4>
The thermoplastic resin fiber according to <1> or <2>, wherein an average fiber diameter of the fine cellulose fiber is 0.1 nm or more and 50 nm or less.
<5>
The thermoplastic resin according to any one of <1> to <4>, wherein the thermoplastic resin is at least one resin selected from the group consisting of polyolefin, polyester, polyamide, polyacrylonitrile, polyphenylene sulfide, and polyether ether ketone. Thermoplastic resin fiber.
<6>
The thermoplastic resin fiber according to any one of <1> to <4>, wherein the thermoplastic resin is at least one resin selected from the group consisting of polyolefin and polyester.

<7>
The thermoplastic resin fiber according to any one of <1> to <4>, wherein the thermoplastic resin is polypropylene.
<8>
Content of the said fine cellulose fiber is 0.01 mass% or more and 50 mass% or less, Preferably it is 0.05 mass% or more, More preferably, it is 0.1 mass% or more, Preferably it is 10 mass% or less, Furthermore Preferably it is 5 mass% or less, Preferably it is 0.05 mass% or more and 10 mass% or less, More preferably, it is 0.1 mass% or more and 5 mass% or less in any one of said <1> thru | or <7>. The thermoplastic resin fiber as described.
<9>
The thermoplastic resin fiber according to any one of <1> to <7>, wherein the content of the fine cellulose fiber is 0.1% by mass or more and 5% by mass or less.
<10>
The content of the thermoplastic resin is 50% by mass or more and 99.99% by mass or less, preferably 90% by mass or more, more preferably 95% by mass or more, preferably 99.95% by mass or less, more preferably 99.9% by mass or less, preferably 90% by mass or more and 99.95% by mass or less, more preferably 95% by mass or more and 99.9% by mass or less, in any one of the above items <1> to <9> The thermoplastic resin fiber as described.
<11>
The average fiber diameter is 150 nm or more and 1500 nm or less, preferably 250 nm or more, more preferably 350 nm or more, preferably 1000 nm or less, more preferably 750 nm or less, preferably 250 nm or more and 1000 nm or less, more preferably 350 nm or more and 750 nm. The thermoplastic resin fiber according to any one of <1> to <10>, wherein:

<12>
The thermoplastic resin fiber according to any one of <1> to <10>, wherein an average fiber diameter is 350 nm or more and 750 nm or less.
<13>
The average fiber diameter is 5 μm or more and 70 μm or less, preferably 7.5 μm or more, more preferably 10 μm or more, preferably 45 μm or less, more preferably 20 μm or less, preferably 7.5 μm or more and 45 μm or less, more preferably The thermoplastic resin fiber according to any one of <1> to <10>, wherein is 10 μm or more and 20 μm or less.
<14>
The thermoplastic resin fiber according to any one of <1> to <10>, wherein the average fiber diameter is 10 μm or more and 20 μm or less.
<15>
The average fiber diameter is 5 μm or more and 70 μm or less, preferably 8 μm or more, more preferably 11 μm or more, preferably 50 μm or less, more preferably 30 μm or less, preferably 8 μm or more and 50 μm or less, more preferably 11 μm or more and 30 μm. The thermoplastic resin fiber according to any one of <1> to <10>, wherein:
<16>
The thermoplastic resin fiber according to any one of <1> to <10>, wherein an average fiber diameter is 11 μm or more and 30 μm or less.

<17>
The thermoplastic resin according to any one of <1> to <16>, wherein the fine cellulose fiber has a structure formed by bonding an aliphatic hydrocarbon group having 1 or more carbon atoms and / or an aromatic hydrocarbon group. fiber.
<18>
The said bond is described in <17>, wherein an aliphatic hydrocarbon group having 1 or more carbon atoms and / or an aromatic hydrocarbon group is connected to a cellulose main chain in the fine cellulose fiber via an amide bond. Thermoplastic resin fiber.
<19>
The aliphatic hydrocarbon group has 1 to 30 carbon atoms, preferably 2 or more, more preferably 3 or more, preferably 20 or less, preferably 2 or more and 30 or less, more preferably 3 or more and 20 The thermoplastic resin fiber according to <17> or <18>, which is the following.
<20>
The thermoplastic resin fiber according to <17> or <18>, wherein the aliphatic hydrocarbon group has 3 to 20 carbon atoms.
<21>
The thermoplastic resin fiber according to any one of <17> to <20>, wherein the aliphatic hydrocarbon group is a saturated or unsaturated linear or branched hydrocarbon group.

<22>
The aromatic hydrocarbon group has 1 to 36 carbon atoms, preferably 8 or more, more preferably 9 or more, preferably 26 or less, preferably 8 to 36, more preferably 9 to 26. The thermoplastic resin fiber according to <17> or <18>, which is the following.
<23>
The thermoplastic resin fiber according to <17> or <18>, wherein the aromatic hydrocarbon group has 9 to 26 carbon atoms.
<24>
A nonwoven fabric comprising the thermoplastic resin fiber according to any one of <1> to <23>.
<25>
A nonwoven fabric comprising the thermoplastic resin fiber according to any one of <1> to <23>, wherein the nonwoven fabric is a spunbond nonwoven fabric or a meltblown nonwoven fabric.
<26>
A nonwoven fabric comprising the thermoplastic resin fiber according to any one of <1> to <23>, wherein the nonwoven fabric is an air-through nonwoven fabric.

<27>
An absorbent article comprising the nonwoven fabric according to any one of <24> to <26>.
<28>
The method for producing a thermoplastic resin fiber according to any one of <1> to <23>, further comprising a step of melt spinning a thermoplastic resin composition containing fine cellulose fibers and a fiber-forming thermoplastic resin.
<29>
A method for producing a thermoplastic resin fiber, comprising melt-spinning a thermoplastic resin composition containing fine cellulose fibers and a fiber-forming thermoplastic resin.
<30>
The fine cellulose fiber is a powder, and includes a step of supplying the mixture of the powder and the thermoplastic resin to an extruder, melt-kneading, and extruding the molten mixture to obtain the thermoplastic resin composition. The method for producing a thermoplastic resin fiber according to <28> or <29>.
<31>
The thermoplastic resin fiber according to any one of <28> to <30>, wherein the melt spinning includes a step of extruding the thermoplastic resin composition in a molten state from a spinneret, and taking up and winding it. Production method.

<32>
The method for producing an air-through nonwoven fabric using the staple fiber by cutting the thermoplastic resin fiber into a staple fiber after the winding step in the method for producing a thermoplastic resin according to <31>.
<33>
The method for producing a thermoplastic resin fiber according to any one of <28> to <30>, wherein the melt spinning step is a melt spinning step by a melt blown method or a spun bond method.
<34>
A method for producing a nonwoven fabric, wherein the melt spinning step in the method for producing a thermoplastic resin according to any one of <28> to <30> is a melt blown method or a spunbond method.

Claims (10)

  A thermoplastic resin fiber in which fine cellulose fibers are dispersed in a fiber-forming thermoplastic resin.   The thermoplastic resin fiber according to claim 1, wherein an average fiber diameter of the fine cellulose fibers is 0.1 nm or more and 300 nm or less.   The thermoplastic resin fiber according to claim 1 or 2, wherein the fine cellulose fiber has a structure formed by bonding an aliphatic hydrocarbon group having 1 or more carbon atoms and / or an aromatic hydrocarbon group.   The thermoplastic resin fiber according to any one of claims 1 to 3, wherein the thermoplastic resin is at least one resin selected from the group consisting of polyolefin and polyester.   The thermoplastic resin fiber according to any one of claims 1 to 4, wherein an average fiber diameter is 1500 nm or less.   The thermoplastic resin fiber according to any one of claims 1 to 4, wherein an average fiber diameter is 5 µm or more and 70 µm or less.   The nonwoven fabric containing the thermoplastic resin fiber as described in any one of Claims 1 thru | or 6.   A method for producing a thermoplastic resin fiber, comprising melt-spinning a thermoplastic resin composition containing fine cellulose fibers and a fiber-forming thermoplastic resin.   The method for producing a thermoplastic resin fiber according to claim 8, wherein the melt spinning includes a step of extruding the thermoplastic resin composition in a molten state from a spinneret, and taking up and winding it.   The method for producing a thermoplastic resin fiber according to claim 8, wherein the melt spinning is a step of melt spinning by a melt blown method or a spun bond method.