Resin fiber, manufacturing method of the same, carbon fiber, manufacturing method of the same, activated carbon fiber, and manufacturing method of the same

Abstract

To provide resin fibers having excellent mechanical properties, carbon fibers and activated carbon fibers using the same, and manufacturing methods of the same.SOLUTION: Provided are a resin fiber composed of a cured product of a resin material comprising a phenolic aralkyl resin; a carbon fiber in which the resin fiber is carbonized; an activated carbon fiber in which the carbon fiber is activated; a manufacturing method of the resin fiber comprising spinning a resin material comprising a phenolic aralkyl resin and curing the obtained filament; a manufacturing method of the carbon fiber comprising carbonizing the resin fiber; and a manufacturing method of the activated carbon fiber comprising carbonizing and activating the resin fiber.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin fiber, a method for producing the same, a carbon fiber, a method for producing the same, an activated carbon fiber, and a method for producing the same. [Background technology]

[0002] Phenolic resin fibers have excellent heat resistance, flame retardancy, and chemical resistance, and are used in a wide range of fields, including general industrial materials where these properties are required. Phenolic resin fibers are also used as raw materials for carbon fibers and activated carbon fibers. Conventional phenolic resin fibers are generally produced by melt-spinning a phenolic resin obtained by reacting a phenol with an aldehyde, and curing (three-dimensional crosslinking) the resulting threads.

[0003] Conventional phenolic resin fibers are extremely brittle, and the fibers that have mechanical properties that can withstand spinning and weaving and are suitable for practical use are limited to those with a fiber diameter of approximately 12 to 25 μm. Therefore, Patent Document 1 proposes a method of mixing a phenolic resin and a fatty acid amide and spinning the mixture, and Patent Document 2 proposes a method of mixing a phenolic resin and a phosphoric acid ester and spinning the mixture. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-246841 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-246840 Summary of the Invention [Problem to be solved by the invention]

[0005] The phenolic resin fibers obtained by the methods of Patent Documents 1 and 2 exhibit mechanical properties (e.g., elongation) that can withstand processing such as spinning, weaving, and nonwoven fabric formation to a certain extent, but depending on the fiber diameter and application, the mechanical properties may be insufficient.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resin fiber having excellent mechanical properties, a carbon fiber and an activated carbon fiber using the same, and methods for producing the same. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] Resin fiber made from a cured resin material containing a phenol aralkyl resin. [2] The resin fiber according to [1], wherein the phenol aralkyl resin has a structure in which two or more phenolic monomer units are bonded via a crosslinking group (r) represented by the following formula (r1) or (r2): [ka] [3] The resin fiber according to [1] or [2], wherein the phenol aralkyl resin has a weight average molecular weight of 1,000 to 100,000. [4] The resin fiber according to any one of [1] to [3], wherein the resin material has a phenol resin content of 0 to 80 mass % relative to the total mass of the phenol aralkyl resin and the phenol resin. [5] The resin fiber according to any one of [1] to [4], which has a fiber diameter of 29 μm or more. [6] A method for producing a resin fiber, comprising spinning a resin material containing a phenol aralkyl resin and curing the resulting yarn. [7] The method for producing a resin fiber according to [6], wherein the phenol aralkyl resin has a structure in which two or more phenolic monomer units are bonded via a crosslinking group (r) represented by the following formula (r1) or (r2): [ka] [8] The method for producing a resin fiber according to [6] or [7], wherein the weight average molecular weight of the phenol aralkyl resin is 1,000 to 100,000. [9] The method for producing a resin fiber according to any one of [6] to [8], wherein the resin material has a phenol resin content of 0 to 80 mass % relative to the total mass of the phenol aralkyl resin and the phenol resin.

[10] The method for producing a resin fiber according to any one of [6] to [9], wherein the fiber diameter of the thread is 29 μm or more.

[11] A carbon fiber obtained by carbonizing the resin fiber according to any one of [1] to [5].

[12] A method for producing carbon fibers, comprising carbonizing the resin fibers according to any one of [1] to [5].

[13] An activated carbon fiber obtained by activating the carbon fiber according to

[11] .

[14] A method for producing activated carbon fibers, which comprises carbonizing and activating the resin fibers according to any one of [1] to [5]. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a resin fiber having excellent mechanical properties, a carbon fiber and an activated carbon fiber using the same, and methods for producing the same. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a graph showing the average elongation of resin fibers in Examples 2 and 3 and Comparative Example 1. [Figure 2] 1 is a graph showing the average elongation of resin fibers in Examples 5 and 6 and Comparative Example 2. [Figure 3] 1 is a graph showing the average elongation of resin fibers in Examples 8 to 10 and Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Resin fiber] A resin fiber according to one embodiment of the present invention is made of a cured resin material containing a phenol aralkyl resin. The resin material may further contain other components in addition to the phenol aralkyl resin, as needed, to the extent that the effects of the present invention are not significantly impaired.

[0011] (phenol aralkyl resin) Phenol aralkyl resins are resins having a structure in which two or more phenolic monomer units are bonded via a divalent crosslinking group having a structure represented by alkylene group-divalent aromatic hydrocarbon group-alkylene group. In the divalent crosslinking group, examples of the divalent aromatic hydrocarbon group include a biphenylene group, a phenylene group, and a naphthylene group. The alkylene group may be linear or branched and may have, for example, 1 to 3 carbon atoms. From the viewpoint of the handleability of the resulting resin, the divalent crosslinking group is preferably a crosslinking group (r) represented by the following formula (r1) or (r2): Therefore, the phenol aralkyl resin preferably has a structure in which two or more phenolic monomer units are bonded via a crosslinking group (r) represented by the following formula (r1) or (r2):

[0012] [ka]

[0013] In formula (r1), the bonding positions of the two methylene groups in the biphenylene ring are not particularly limited, but the 4- and 4'-positions are preferred because the crosslinking agent having these groups used in the production is relatively inexpensive and has good reactivity with phenolic monomers. In formula (r2), the bonding positions of the two methylene groups in the benzene ring are not particularly limited, but the para-position is preferred because the crosslinking agent having this group, which is used in the production, is relatively inexpensive and has good reactivity with phenolic monomers. When the phenol aralkyl resin has a crosslinking group (r), the crosslinking group (r) in the phenol aralkyl resin may be only a group represented by formula (r1), only a group represented by formula (r2), or both.

[0014] Phenolic monomers are compounds that contain an aromatic ring and a hydroxyl group attached to the aromatic ring. A phenolic monomer unit typically has a structure in which one or more hydrogen atoms have been removed from the aromatic ring to which the hydroxyl group of the phenolic monomer is attached. Examples of phenolic monomers include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 3,5-xylenol, m-ethylphenol, m-propylphenol, m-butylphenol, p-butylphenol, o-butylphenol, resorcinol, hydroquinone, catechol, 3-methoxyphenol, 4-methoxyphenol, 3-methylcatechol, 4-methylcatechol, methylhydroquinone, 2-methylresorcinol, 2,3-dimethylhydroquinone, 2,5-dimethylresorcinol, 2-ethoxyphenol, 4-ethoxyphenol, 4-ethylresorcinol, 3-ethoxy-4-methoxyphenol, 2-propenylphenol, 2-isopropylphenol, 3-isopropylphenol, 4-isopropylphenol, 3,4,5-trimethylphenol, 2-isopropoxyphenol, 4-propoxyphenol, 2-allylphenol, 3,4,5-trimethoxyphenol, phenol, 4-isopropyl-3-methylphenol, pyrogallol, phloroglucinol, 1,2,4-benzenetriol, 5-isopropyl-3-methylphenol, 4-butoxyphenol, 4-t-butylcatechol, t-butylhydroquinone, 4-t-pentylphenol, 2-t-butyl-5-methylphenol, 2-phenylphenol, 3-phenylphenol, 4-phenylphenol, 3-phenoxyphenol, 4-phenoxyphenol, 4-hexyloxyphenol, 4-hexanoylresorcinol, 3,5-diisopropylcatechol, 4-hexylresorcinol, 4-heptyloxyphenol, 3,5-di-t-butylphenol, 3,5-di-t-butylcatechol, 2,5-di-t-butylhydroquinone, di-sec-butylphenol, 4-cumylphenol, nonylphenol, 2-cyclopentylphenol, 4-cyclopentylphenol, bisphenol A, bisphenol F, and the like. Of these, the compound represented by the following formula (m1) is preferred.

[0015] [ka]

[0016] In the formula, n represents an integer of 0 to 3. 1 represents a linear or branched hydrocarbon group having 1 to 3 carbon atoms, and when n is 2 or 3, n R 1 may be the same or different. R 1 may be a saturated or unsaturated hydrocarbon group. Among the compounds represented by formula (m1), phenol, o-cresol, m-cresol and p-cresol are preferred, and phenol is most preferred. The phenol aralkyl resin may have one or more types of phenolic monomer units.

[0017] The phenol aralkyl resin may or may not have a branched structure. For example, phenol has high reactivity at two ortho positions and one para position relative to the bonding position of the hydroxyl group on the benzene ring. Therefore, when the phenolic monomer unit contains a phenol unit, the phenol unit can be the branching point of the phenol aralkyl resin. An example of the unbranched phenol aralkyl resin is one represented by the following formula (L).

[0018] [ka]

[0019] In the formula, a represents an integer of 0 or more, n represents an integer of 0 to 3, and (a+2) n's may be the same or different. 1 represents a linear or branched hydrocarbon group having 1 to 3 carbon atoms, and R 1 If there are two or more R 1 may be the same or different. 2 represents the divalent crosslinking group (preferably the crosslinking group (r)), and when a is an integer of 1 or more, (a+1) R 2 may be the same or different.

[0020] The weight-average molecular weight (Mw) of the phenol aralkyl resin is preferably 1,000 to 100,000, more preferably 5,000 to 50,000, and even more preferably 10,000 to 20,000. When Mw is equal to or greater than the lower limit, the minimum viscosity necessary for melt spinning is easily achieved. When Mw is equal to or less than the upper limit, the viscosity during melting does not become too high, resulting in good spinnability. Mw is measured by gel permeation chromatography (GPC) using polystyrene as a standard.

[0021] The phenol aralkyl resins may be used alone or in combination of two or more. The phenol aralkyl resin may be one produced by a known method or a commercially available one.

[0022] The phenol aralkyl resin can be produced, for example, by reacting a phenolic monomer with a crosslinking agent having a structure corresponding to the divalent crosslinking group. Examples of crosslinking agents include those having a structure in which an alkoxy group having 1 to 4 carbon atoms or a halogen atom is bonded to each end of the divalent crosslinking group. For example, by using at least one crosslinking agent selected from the group consisting of compounds represented by the following formula (1) and compounds represented by the following formula (2), a phenol aralkyl resin having a crosslinking group (r) as the divalent crosslinking group can be obtained.

[0023] [ka] In the formula, X represents an alkoxy group having 1 to 4 carbon atoms or a halogen atom.

[0024] Examples of the halogen atom for X include a chlorine atom and a bromine atom. Examples of the compound represented by the formula (1) include 4,4'-bis(alkoxymethyl)biphenyl, 2,2'-bis(alkoxymethyl)biphenyl, 2,4'-bis(alkoxymethyl)biphenyl, 4,4'-bis(halogenated methyl)biphenyl, 2,2'-bis(halogenated methyl)biphenyl, 2,4'-bis(halogenated methyl)biphenyl, and the like (wherein the alkoxy group has 1 to 4 carbon atoms). Examples of the compound represented by the formula (2) include paraxylylene glycol dialkyl ether, metaxylylene glycol dialkyl ether, 1,4-bis(halogenated methyl)benzene, and the like (where the alkyl group has 1 to 4 carbon atoms). Among the above crosslinking agents, 4,4'-bis(alkoxymethyl)biphenyl, 4,4'-bis(halogenated methyl)biphenyl, paraxylylene glycol dialkyl ether, and 1,4-bis(halogenated methyl)benzene are preferred because they are relatively inexpensive and have good reactivity with phenolic monomers. The crosslinking agent may be used alone or in combination of two or more kinds.

[0025] The molar ratio of crosslinking agent to phenolic monomer is preferably 0.1 to 1, more preferably 0.5 to 0.8. When the ratio of crosslinking agent is equal to or greater than the lower limit, the amount of phenolic monomer remaining after the reaction is reduced, resulting in a good yield. When the ratio of crosslinking agent is equal to or less than the upper limit, the weight-average molecular weight is likely to be equal to or less than the preferred upper limit.

[0026] The reaction between the phenolic monomer and the crosslinking agent can be carried out in the presence of an acidic catalyst, which increases the reaction rate between the phenolic monomer and the crosslinking agent. In particular, when X in the crosslinking agent is an alkoxy group, it is preferable to carry out the reaction in the presence of an acidic catalyst. If the X in the crosslinking agent is a halogen atom, there is no need to add a separate acidic catalyst. When X is a halogen atom, the halogen atom is eliminated by the heat generated during the reaction, forming HX. Because this HX functions as an acidic catalyst, the reaction rate is sufficiently fast even without the addition of a separate acidic catalyst.

[0027] The acid catalyst is not particularly limited as long as it allows the reaction to proceed. Examples include hydrochloric acid, sulfuric acid, phosphoric acid, oxalic acid, trifluoroacetic acid, p-toluenesulfonic acid, methanesulfonic acid, boron trifluoride, aluminum chloride, iron chloride, zinc chloride, etc. The acid catalyst may be used alone or in combination of two or more. The amount of the acid catalyst used is preferably 0.01 to 30.0% by mass, more preferably 0.5 to 10.0% by mass, based on the phenolic monomer.

[0028] The reaction temperature between the phenolic monomer and the crosslinking agent is preferably 50 to 250° C., more preferably 100 to 180° C. If the reaction temperature is too low, the reaction does not proceed, whereas if the reaction temperature is too high, it becomes difficult to control the reaction, making it difficult to stably obtain the target phenol aralkyl resin. The reaction time is, for example, 1 to 10 hours. At the end of the reaction, an alkali may be added to the resulting reaction product to neutralize the acidic catalyst. After the reaction of the phenolic monomer with the crosslinking agent, the reaction product may be subjected to treatments such as removal of unreacted raw materials by distillation or the like, concentration, and purification (washing, column chromatography, etc.), if necessary.

[0029] (Other ingredients) The resin material may include, for example, a phenolic resin. Phenolic resins are resins obtained by reacting a phenolic monomer with an aldehyde. Examples of phenolic resins that can be used include novolak-type phenolic resins obtained by reacting a phenolic monomer with an aldehyde in the presence of an acidic catalyst, resol-type phenolic resins obtained by reacting a phenolic monomer with an aldehyde in the presence of a basic catalyst, modified phenolic resins, and mixtures thereof.

[0030] Examples of the phenolic monomer include the same as those mentioned above. Examples of aldehydes include formaldehyde, trioxane, furfural, paraformaldehyde, benzaldehyde, methyl hemiformal, ethyl hemiformal, propyl hemiformal, salicylaldehyde, butyl hemiformal, phenyl hemiformal, acetaldehyde, propyl aldehyde, phenylacetaldehyde, α-phenylpropyl aldehyde, β-phenylpropyl aldehyde, o-hydroxybenzaldehyde, m-hydroxybenzaldehyde, p-hydroxybenzaldehyde, o-chlorobenzaldehyde, o-nitrobenzaldehyde, m-nitrobenzaldehyde, p-nitrobenzaldehyde, o-methylbenzaldehyde, m-methylbenzaldehyde, p-methylbenzaldehyde, p-ethylbenzaldehyde, and p-n-butylbenzaldehyde. Among these, formaldehyde, paraformaldehyde, furfural, benzaldehyde, and salicylaldehyde are preferred, with formaldehyde and paraformaldehyde being particularly preferred. One type of aldehyde may be used alone, or two or more types may be used in combination.

[0031] Examples of acidic catalysts for obtaining novolac phenolic resins include hydrochloric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, oxalic acid, butyric acid, lactic acid, benzenesulfonic acid, p-toluenesulfonic acid, boric acid, and salts with metals such as zinc chloride and zinc acetate. One type of acidic catalyst may be used alone, or two or more types may be used in combination. Examples of basic catalysts for obtaining resol-type phenolic resins include alkali metal hydroxides such as sodium hydroxide and lithium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide and barium hydroxide, ammonium hydroxide, and amines such as diethylamine, triethylamine, triethanolamine, ethylenediamine, and hexamethylenetetramine. The basic catalysts may be used alone or in combination of two or more. Examples of modified phenolic resins include novolac-type or resol-type phenolic resins modified by known techniques such as boron modification, silicon modification, heavy metal modification, nitrogen modification, sulfur modification, oil modification, and rosin modification.

[0032] As the phenolic resin, any of novolac-type phenolic resins, resol-type phenolic resins, and modified phenolic resins can be used. However, resol-type resins have inferior thermal stability compared to novolac-type resins, and polymerization easily proceeds when heated during melting, which inevitably leads to solidification in the melt spinning apparatus, making continuous, stable spinning difficult. Therefore, taking into consideration the ease of the process and versatility in industrial production, novolac-type phenolic resins, modified phenolic resins obtained by modifying novolac-type phenolic resins, or mixtures thereof are preferred. The phenolic resins may be used alone or in combination of two or more. The phenolic resin to be used may be one produced by a known method or a commercially available one.

[0033] The resin material may contain additives, such as fatty acid amides, phosphate esters, plasticizers, compatibilizers, antioxidants, UV absorbers, penetrating agents, thickeners, antifungal agents, dyes, pigments, and fillers.

[0034] Fatty acid amides refer to non-polymers having a structure in which one or more hydrogen atoms bonded to the nitrogen atom of ammonia or amine are replaced by acyl groups, and include primary amides in which two hydrogen atoms are bonded to the nitrogen atom, secondary amides in which one hydrogen atom is bonded to the nitrogen atom, tertiary amides in which no hydrogen atoms are bonded to the nitrogen atom, lactams, and those having two or more amine nitrogen atoms per molecule. Therefore, fatty acid amides are different from polymers such as so-called aliphatic polyamides, represented by nylon-6 and nylon-6,6. Fatty acid amides are also called fatty acid amides. Specific examples of fatty acid amides include those described in JP-A-2012-052283.

[0035] Phosphate esters are those in which one or more of the -OH groups in the phosphoric acid are replaced with R 3 -O-(AO) m -(However, R3 is a hydrocarbon group having 4 or more carbon atoms which may have a heteroatom (an atom other than carbon and hydrogen atoms), AO is an oxyalkylene group having 2 to 4 carbon atoms, and m is a number from 0 to 100 which indicates the average number of repetitions of AO), or a salt thereof. Phosphoric acid is tetraphosphorus decaoxide (PO 10 ) is a general term for various oxoacids produced by hydrolysis, and includes orthophosphate, pyrophosphate (diphosphate), triphosphate, tetraphosphate, metaphosphate, etc. Specific examples of phosphate esters include those described in JP-A-2012-026077.

[0036] (resin material) The content of the phenol aralkyl resin in the resin material is preferably 20% by mass or more, more preferably 50% by mass or more, and even more preferably 80% by mass or more, and may be 100% by mass, based on the total mass of the resin material. When the content of the phenol aralkyl resin is equal to or more than the lower limit, the mechanical properties of the resin fiber, particularly the elongation, tend to be better.

[0037] In the resin material, the total content of the phenol aralkyl resin and the phenol resin is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass, based on the total mass of the resin material.

[0038] The content of the phenol resin in the resin material is preferably 0 to 80% by mass, more preferably 0 to 50% by mass, and even more preferably 0 to 20% by mass, based on the total mass of the phenol aralkyl resin and the phenol resin. A lower content of the phenol resin tends to result in better mechanical properties, particularly elongation, of the resin fiber. When the resin material contains a phenol resin, the content of the phenol resin is, for example, 20% by mass or more, or even 50% by mass or more, based on the total mass of the phenol aralkyl resin and the phenol resin.

[0039] When the fiber diameter of the resin fiber is 39 μm or more (fineness is 13D or more), the resin material preferably contains 50 to 100 mass% of phenol aralkyl resin and 0 to 50 mass% of phenol resin, and more preferably 70 to 100 mass% of phenol aralkyl resin and 0 to 30 mass% of phenol resin, based on the total mass of the resin material. It is particularly preferable that the resin material does not contain phenol resin. The resin material may further contain components other than the phenol aralkyl resin and phenol resin.

[0040] When the fiber diameter of the resin fiber is 29 μm or more (fineness 7D) but less than 39 μm, the resin material preferably contains 40 to 100 mass% of phenol aralkyl resin and 0 to 60 mass% of phenol resin, and more preferably 60 to 100 mass% of phenol aralkyl resin and 0 to 40 mass% of phenol resin, based on the total mass of the resin material. It is particularly preferable that the resin material does not contain phenol resin. The resin material may further contain components other than the phenol aralkyl resin and phenol resin.

[0041] When the fiber diameter of the resin fiber is less than 29 μm (fineness less than 7D), the resin material preferably contains 30 to 100 mass% of phenol aralkyl resin and 0 to 70 mass% of phenol resin, and more preferably 50 to 100 mass% of phenol aralkyl resin and 0 to 50 mass% of phenol resin, relative to the total mass of the resin material. It is particularly preferable that the resin material does not contain phenol resin. The resin material may further contain components other than the phenol aralkyl resin and phenol resin.

[0042] When the resin material contains other components, the resin material can be prepared by mixing the phenol aralkyl resin with the other components. The mixing method is not particularly limited. For example, a method of melt-mixing a phenol aralkyl resin with other components, or a method of melt-mixing a phenol aralkyl resin with other components using a solvent can be mentioned. Among these, the method of melt-mixing a phenol aralkyl resin with other components is preferred from the viewpoints of process simplicity, environmental load, and economic efficiency.

[0043] As a method for melt-mixing the phenol aralkyl resin with other components, for example, a method for heating and kneading the phenol aralkyl resin with other components can be mentioned. Heat kneading can be carried out using a known kneading device such as an extruder-type kneader, a mixing roll, a Banbury mixer, or a high-speed twin-screw continuous mixer. The heat-kneading temperature may be appropriately selected depending on the properties of the raw materials, and is preferably 200°C or lower, more preferably 140 to 180°C. By setting the heat-kneading temperature at or below the preferred upper limit, it is easy to suppress thermal denaturation and deterioration of the raw materials due to exposure to high temperatures. By setting the heat-kneading temperature at or above the preferred lower limit, it becomes possible to efficiently mix the two. The heating and kneading time is preferably 15 minutes or more, more preferably 30 to 120 minutes. By setting the heating and kneading time to the preferred lower limit or more, it becomes possible to mix the two more uniformly. By setting the heating and kneading time to the preferred upper limit or less, it becomes easy to suppress thermal denaturation and deterioration of the raw materials.

[0044] In the method of dissolving and mixing the phenol aralkyl resin and other components using a solvent, the phenol aralkyl resin and other components are dissolved and mixed in a solvent capable of dissolving them, and then the solvent is removed by evaporation. The solvent can be appropriately selected from, for example, ketone solvents, ether solvents, nitrogen-containing solvents, hydrocarbon solvents, ester solvents, alcohol solvents, and mixed solvents of two or more of these solvents. When dissolving and mixing the phenol aralkyl resin and the fatty acid amides, it is preferable to gradually add the phenol aralkyl resin and the fatty acid amides while stirring the solvent. In this case, if the phenol aralkyl resin or the fatty acid amides are difficult to dissolve in the solvent, heating is effective. Furthermore, applying pressure makes it possible to heat the mixture to a temperature above the boiling point of the solvent at normal pressure, which is even more effective. However, since exposing the raw materials to high temperatures may cause thermal denaturation and deterioration, it is preferable to limit heating until the raw materials are completely dissolved.

[0045] The phenol aralkyl resin may be mixed with other components by a method other than the above-mentioned melt mixing and dissolution mixing. For example, a resin material can be prepared by blending other components during the synthesis reaction of the phenol aralkyl resin, as long as the other components do not inhibit the synthesis reaction of the phenol aralkyl resin and do not cause deterioration of the raw materials at the temperature during the synthesis reaction.

[0046] (Characteristics of resin fibers) The fiber diameter of the resin fiber is, for example, 10 to 100 μm, or further 15 to 60 μm. The fiber diameter is measured by the method described in the examples below. The fineness of the resin fiber is, for example, 1 to 85 denier (1.1 to 94.4 dtex), or further 2 to 30 denier (2.2 to 33.3 dtex). Hereinafter, denier may also be abbreviated as D. The fineness is measured by the method described in the examples below.

[0047] In a preferred embodiment, the resin fiber has a fiber diameter of 29 μm or more (fineness of 7D or more), and further 39 μm or more. The upper limit of the fiber diameter is not particularly limited, but is, for example, 100 μm or less, and further 60 μm or less. Resin fibers having a fiber diameter of 29 μm or more are useful for applications such as adsorption filters.

[0048] In another preferred embodiment, the resin fiber has a fiber diameter of less than 29 μm (fineness less than 7D), or even 18 μm or less. The lower limit of the fiber diameter is not particularly limited, but is, for example, 10 μm or more, or even 15 μm or more. Resin fibers with a fiber diameter of less than 29 μm are useful for applications such as flame-retardant sheets.

[0049] From the viewpoint of processability, the average elongation of the resin fiber is preferably 10% or more, more preferably 15% or more. The upper limit is not particularly limited, but is, for example, 100%. The average elongation is measured by the method described in the examples below.

[0050] (Method of manufacturing resin fibers) The resin fiber of this embodiment can be produced, for example, by spinning the above-mentioned resin material and curing the resulting thread.

[0051] <Spinning> The resin material is spun into uncured threads. The spinning method can be appropriately selected from known methods such as wet spinning, dry spinning, dry-wet spinning, melt spinning, gel spinning, liquid crystal spinning, etc., taking into consideration the properties of the resin material, etc. Among these, melt spinning is preferred because of the simplicity of the apparatus and its economical advantages.

[0052] The melt spinning can be carried out using a common melt spinning device. As the melting device of the melt spinning device, a grid melter type, a single screw extruder type, a twin screw extruder type, a tandem extruder type, etc. can be used. In order to prevent oxidation of the molten resin material, the inside of the melt spinning apparatus may be purged with nitrogen, or an extruder equipped with a vent may be used to remove traces of residual solvent or monomers.

[0053] The temperature during melt spinning (melt spinning temperature) is preferably 100 to 200°C, more preferably 110 to 140°C. When the melt spinning temperature is equal to or higher than the lower limit, the molten resin material can be easily discharged. When the melt spinning temperature is equal to or lower than the upper limit, the phenol aralkyl resin can be prevented from reacting or being denatured by heat during melt spinning.

[0054] As the spinneret, a known one can be used. The hole diameter of the spinneret is set so that the resulting yarn has a desired fiber diameter and fineness. The ratio of the length L to the diameter D of the capillary part of the spinneret (hereinafter also referred to as "L / D") is preferably 0.5 or more and less than 10, more preferably 1 to 5. When L / D is within the above range, the stability of the spinning state is more excellent. In the case of special fiber manufacturing methods (for example, in the case of parallel type composite fibers, core-sheath type composite fibers, or sea-island type composite fibers), a side-by-side type or sheath-core type, or a conjugate spinneret that combines a third component polymer, can also be used.

[0055] The spinning speed is preferably 15 m / min or more and less than 3000 m / min, more preferably 30 m / min or more and less than 2000 m / min, and even more preferably 50 m / min or more and less than 1600 m / min. By setting the spinning speed to the preferred lower limit or more, spinning can be performed efficiently. By setting the spinning speed to less than the preferred upper limit, the occurrence of yarn breakage during spinning can be suppressed.

[0056] <Curing> By curing the uncured yarn, mechanical properties such as elongation and strength are improved. Any known method can be used for the curing method, for example, the uncured yarn can be cured by contacting it with an aqueous treatment liquid containing a catalyst and, if necessary, an aldehyde.

[0057] Examples of the catalyst include basic catalysts such as amines such as ammonium hydroxide, diethylamine, triethylamine, triethanolamine, ethylenediamine, and hexamethylenetetramine, and mixtures thereof; and acidic catalysts such as acids such as hydrochloric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, oxalic acid, butyric acid, lactic acid, benzenesulfonic acid, p-toluenesulfonic acid, and boric acid, salts of these acids with metals (e.g., zinc chloride and zinc acetate), and mixtures thereof. One type of catalyst may be used alone, or two or more types may be used in combination. The catalyst is preferably an acidic catalyst.

[0058] Examples of aldehydes include formaldehyde, trioxane, furfural, paraformaldehyde, benzaldehyde, methyl hemiformal, ethyl hemiformal, propyl hemiformal, salicylaldehyde, butyl hemiformal, phenyl hemiformal, acetaldehyde, propyl aldehyde, phenylacetaldehyde, α-phenylpropyl aldehyde, β-phenylpropyl aldehyde, o-hydroxybenzaldehyde, m-hydroxybenzaldehyde, p-hydroxybenzaldehyde, o-chlorobenzaldehyde, o-nitrobenzaldehyde, m-nitrobenzaldehyde, p-nitrobenzaldehyde, o-methylbenzaldehyde, m-methylbenzaldehyde, p-methylbenzaldehyde, p-ethylbenzaldehyde, and p-n-butylbenzaldehyde. Among these, formaldehyde, paraformaldehyde, furfural, benzaldehyde, and salicylaldehyde are preferred, with formaldehyde and paraformaldehyde being particularly preferred. One type of aldehyde may be used alone, or two or more types may be used in combination.

[0059] When a treatment liquid is used, curing is preferably carried out by heating in the treatment liquid at a temperature of 60° C. or higher and lower than 110° C. for 3 hours or higher and lower than 30 hours. Curing may also be achieved by heating in the gas phase. After being heat-cured in the treatment liquid, the film may be washed with water, dried, and further cured by heating at a temperature of 100 to 300° C. in an inert gas such as nitrogen, helium, or carbon dioxide gas. In addition, known hardening treatments can be carried out.

[0060] The method of contacting with the treatment liquid is not particularly limited, but examples include a batchwise curing method in which staple- or tow-shaped uncured yarn is immersed in the treatment liquid in a reaction vessel, a method in which uncured yarn processed into a bobbin or hank is contacted with the treatment liquid to cure, and a method in which tow-shaped uncured yarn is continuously contacted with the treatment liquid to cure. After contact with the treatment solution, the catalyst is neutralized, the yarn is washed, etc., if necessary.

[0061] (Application) The use of the resin fiber of this embodiment is not particularly limited, and for example, it can be used in various applications to which phenolic resin fibers have conventionally been applied. For example, the resin fiber of this embodiment can be processed by spinning, weaving, nonwoven fabric, etc. to form textile products such as spun yarn, woven fabric, nonwoven fabric, etc. Since phenol aralkyl resins have excellent flame retardancy, textile products using the resin fiber of this embodiment exhibit flame retardancy. The resin fiber of this embodiment may be carbonized to form carbon fiber. The resin fiber of this embodiment may be carbonized and activated to form activated carbon fiber. When the resin fibers are carbonized, the resin fibers may be processed into a fiber product before carbonization.

[0062] Carbonization can be performed by a conventionally known method of heating in the presence of an inert gas. The inert gas used for carbonization includes a gas that does not substantially contain oxygen, such as nitrogen, helium, argon, hydrogen, carbon monoxide, carbon dioxide, etc. The temperature during carbonization is preferably in the range of 480 to 1200°C, more preferably in the range of 520 to 1000°C, and even more preferably in the range of 600 to 900°C. Carbonization can be carried out using a multi-stage furnace, a rotary kiln furnace, a fluidized bed furnace, or the like.

[0063] The activation can be performed by a known activation method such as a gas activation method or a chemical activation method. In the gas activation method, carbon fibers are activated by contacting them with an activation gas, such as water vapor, air, carbon monoxide, carbon dioxide, hydrogen chloride, oxygen, or a mixture thereof. In the chemical activation method, carbon fibers are activated by contacting them with a chemical, such as alkali metal hydroxides (e.g., sodium hydroxide, potassium hydroxide, etc.), alkaline earth metal hydroxides (e.g., calcium hydroxide, etc.), inorganic acids (e.g., boric acid, phosphoric acid, sulfuric acid, hydrochloric acid, etc.), or inorganic salts (e.g., zinc chloride, etc.). In the case of the chemical activation method, after activation, the product or the chemical used may be neutralized with an acid or alkali, or may be removed by washing with water or the like. Among the above activation methods, the gas activation method is preferred, and the gas activation method using water vapor is particularly preferred, in view of the simplicity of the equipment and the fact that no special treatment is required after activation. The activation can be carried out using a multi-stage furnace, a rotary kiln furnace, a fluidized bed furnace, or the like. [Example]

[0064] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass."

[0065] [Evaluation method] (fiber diameter) The fiber diameter of the resin fiber was measured using a KH-3000 digital microscope manufactured by Hirox Corporation.

[0066] (fineness) The fineness of the resin fiber was measured using a DC11B denier computer manufactured by Search Co., Ltd.

[0067] (Average elongation) The average elongation was the average value of the elongation (elongation rate) of 10 resin fibers. The elongation of the resin fiber was measured using an RTG-1210 Tensilon universal testing machine manufactured by A&D Co., Ltd., in accordance with the method of JIS L 1015.

[0068] (specific surface area) Specific surface area of ​​activated carbon fiber (m 2 / g) was measured using Bellsorp MAX X manufactured by Microtrac-Bell Corporation.

[0069] [Production of resin materials] (Production Example 1: Production of phenol aralkyl resin) A 1-L separable flask equipped with a thermometer, stirrer, condenser, and dropping funnel was charged with 7.37 g of methanol, 210.6 g of phenol, and 0.49 g of diethyl sulfate and heated to 136°C. 269 g of paraxylene glycol dimethyl ether was added dropwise to the solution over 7 hours, and stirring at 136°C was continued for 2 hours. The pressure was then reduced to 360 mmHg over 40 minutes to distill off the methanol, and the mixture was opened to the atmosphere and then heated. After reaching 157°C, the pressure was reduced to 40 mmHg over 1 hour to distill off the phenol. The mixture was allowed to cool and solidify, yielding a phenol aralkyl resin (hereinafter also referred to as PA-1). The Mw of PA-1 was 19918.

[0070] (Production Example 2: Production of phenol aralkyl resin) A phenol aralkyl resin (hereinafter also referred to as PA-2) was obtained in the same manner as in Production Example 1, except that 7.48 g of methanol, 213.7 g of phenol, 0.49 g of diethyl sulfate, and 264 g of paraxylene glycol dimethyl ether were used. The Mw of PA-2 was 10,849.

[0071] (Production Example 3: Production of phenolic resin) A 1-L separable flask equipped with a thermometer, stirrer, and condenser was charged with 500.0 g of phenol, 353.5 g of 37% formalin, and 2.5 g of oxalic acid, and the mixture was heated to 100°C over 40 minutes. Stirring at 100°C was continued for 4 hours, and the mixture was then heated to 200°C for dehydration and concentration. The mixture was then allowed to cool and solidify, yielding a phenolic resin (hereinafter also referred to as P-1). The Mw of P-1 was 6504.

[0072] (Production Example 4: Production of behenic acid amide mixed phenolic resin) A 1-L separable flask equipped with a thermometer, stirrer, and condenser was charged with 500.0 g of phenol, 366.5 g of 37% formalin, and 2.5 g of oxalic acid, and the mixture was heated to 100°C over 40 minutes. Stirring at 100°C was continued for 4 hours, and the mixture was then heated to 200°C and dehydrated and concentrated. The reaction mixture was allowed to cool to 165°C, and 29.7 g of behenic acid amide was added under a nitrogen gas flow. Stirring was continued for 1 hour at 165°C, and the mixture was allowed to cool and solidify, yielding a behenic acid amide-mixed phenolic resin (hereinafter also referred to as P-2). The Mw of P-2 was 10,825.

[0073] (Production Example 5: Production of a 5:5 mixed resin of phenol aralkyl resin and phenol resin) 50 parts by mass of PA-1 obtained in Production Example 1 and 50 parts by mass of P-1 obtained in Production Example 3 were added to a separable flask equipped with a thermometer, a stirrer, and a condenser, and the mixture was stirred at 150°C for 1 hour, after which it was allowed to cool and solidify, yielding a mixed resin with a PA-1:P-1 = 5:5 (mass ratio).

[0074] (Production Example 6: Production of a mixed resin of phenol aralkyl resin:phenol resin = 8:2) A mixed resin with a PA-1:P-1 ratio of 8:2 (mass ratio) was obtained in the same manner as in Production Example 5, except that 80 parts by mass of PA-1 and 20 parts by mass of P-1 were used.

[0075] [Production of resin fibers] Example 1 The PA-2 obtained in Production Example 2 was crushed and then introduced into a nozzle equipped with a thermometer, a nichrome wire heater, and a monohole at the bottom. The temperature of the nozzle was raised to melt the resin, and then nitrogen gas was applied from above the nozzle to pressurize the melt, and the molten material was spun into 3D (18 μm) equivalent yarns. The resulting thread was then immersed in a 17.5-18.0% aqueous solution of hydrochloric acid and 9.5-10.0% formalin in a plastic bottle and heated at approximately 95°C for 7 hours to cause a curing reaction. After the curing reaction, the thread was neutralized, washed, and dried to obtain pale yellow resin fibers.

[0076] Example 2 Resin fibers were obtained in the same manner as in Example 1, except that PA-1 obtained in Production Example 1 was used instead of PA-2.

[0077] Example 3 Resin fibers were obtained in the same manner as in Example 1, except that the mixed resin obtained in Production Example 6 was used instead of PA-1.

[0078] (Comparative Example 1) Resin fibers were obtained in the same manner as in Example 1, except that P-1 obtained in Production Example 3 was used instead of the phenol aralkyl resin.

[0079] Example 4 Resin fibers were obtained in the same manner as in Example 1, except that the spinning conditions were adjusted so that the threads were equivalent to 10D (34.3 μm).

[0080] Example 5 Resin fibers were obtained in the same manner as in Example 4, except that PA-1 obtained in Production Example 1 was used instead of PA-2.

[0081] Example 6 Resin fibers were obtained in the same manner as in Example 4, except that the mixed resin obtained in Production Example 5 was used instead of PA-2.

[0082] (Comparative Example 2) Resin fibers were obtained in the same manner as in Example 4, except that P-2 obtained in Production Example 4 was used instead of PA-2.

[0083] Example 7 Resin fibers were obtained in the same manner as in Example 1, except that the spinning conditions were adjusted so that the threads were equivalent to 19D (47.3 μm).

[0084] Example 8 Resin fibers were obtained in the same manner as in Example 7, except that PA-1 obtained in Production Example 1 was used instead of PA-2.

[0085] Example 9 Resin fibers were obtained in the same manner as in Example 7, except that the mixed resin obtained in Production Example 6 was used instead of PA-2.

[0086] Example 10 Resin fibers were obtained in the same manner as in Example 7, except that the mixed resin obtained in Production Example 5 was used instead of PA-2.

[0087] (Comparative Example 3) Resin fibers were obtained in the same manner as in Example 7, except that P-2 obtained in Production Example 4 was used instead of PA-2.

[0088] The resin fibers obtained in Examples 7 to 10 and Comparative Example 3 had finenesses ranging from 16 to 22D with an average of 19D, and fiber diameters ranging from 43.3 to 50.5µm with an average of 47.3µm.

[0089] The average elongation of the obtained resin fibers (after curing) was measured. The results are shown in Tables 1 to 3. Furthermore, the results of Examples 2 and 3 and Comparative Example 1 are shown in Figure 1, the results of Examples 5 and 6 and Comparative Example 2 are shown in Figure 2, and the results of Examples 8 to 10 and Comparative Example 3 are shown in Figure 3. The resin materials used in each example are shown in each figure.

[0090] [Table 1]

[0091] [Table 2]

[0092] [Table 3]

[0093] When compared with resin fibers having a fineness of 3D, as shown in Table 1 and FIG. 1, the resin fibers of Examples 1 to 3 were superior to Comparative Example 1 in average elongation. When compared with resin fibers having a fineness of 10D, the resin fibers of Examples 4 to 6 were superior to Comparative Example 2 in average elongation, as shown in Table 2 and FIG. When compared with resin fibers having a fineness of 19D, as shown in Table 3 and Fig. 3, the resin fibers of Examples 7 to 10 were superior in average elongation to Comparative Example 3. In particular, the average elongation of Examples 7 to 9, in which the content of the phenol resin was 20 mass% or less with respect to the total mass of the phenol aralkyl resin and the phenol resin, was superior.

[0094] [Production of activated carbon fiber] Example 11 The resin fiber obtained in Example 1 was placed in a quartz tube with an inner diameter of 70 mm and heated in a nitrogen stream from room temperature to 900°C at a heating rate of 5°C / min. At this point, nitrogen gas was introduced into hot water previously adjusted to 80°C, and a mixed gas of nitrogen and water vapor was introduced into the quartz tube for 10 minutes. Subsequently, the tube was cooled while introducing only nitrogen, thereby obtaining activated carbon fiber.

[0095] Example 12 Activated carbon fibers were obtained in the same manner as in Example 11, except that the resin fibers obtained in Example 2 were used instead of the resin fibers obtained in Example 1.

[0096] Comparative Example 4 Activated carbon fibers were obtained in the same manner as in Example 11, except that the resin fibers obtained in Comparative Example 1 were used instead of the resin fibers obtained in Example 1.

[0097] The specific surface area of ​​the obtained activated carbon fiber was measured, and the results are shown in Table 4.

[0098] [Table 4]

[0099] As shown in the above results, activated carbon fibers could be produced by carbonizing and activating the resin fibers of Examples 1 and 2. Furthermore, the obtained activated carbon fibers had a specific surface area equal to or greater than that of conventional activated carbon fibers using phenolic resins.

Claims

1. A resin fiber made of a cured resin material containing a phenol aralkyl resin.

2. The resin fiber according to claim 1, wherein the phenol aralkyl resin has a structure in which two or more phenolic monomer units are bonded via a crosslinking group (r) represented by the following formula (r1) or (r2): 【Chemical 1】

3. The resin fiber according to claim 1 or 2, wherein the weight average molecular weight of the phenol aralkyl resin is 1,000 to 100,000.

4. The resin fiber according to claim 1 or 2, wherein the resin material has a phenol resin content of 0 to 80 mass % relative to the total mass of the phenol aralkyl resin and the phenol resin.

5. The resin fiber according to claim 1 or 2, having a fiber diameter of 29 μm or more.

6. A method for producing a resin fiber, comprising spinning a resin material containing a phenol aralkyl resin and curing the resulting yarn.

7. The method for producing a resin fiber according to claim 6, wherein the phenol aralkyl resin has a structure in which two or more phenol-based monomer units are bonded via a crosslinking group (r) represented by the following formula (r1) or (r2): 【Chemistry 2】

8. The method for producing a resin fiber according to claim 6 or 7, wherein the weight average molecular weight of the phenol aralkyl resin is 1,000 to 100,000.

9. The method for producing a resin fiber according to claim 6 or 7, wherein the resin material has a phenol resin content of 0 to 80 mass % relative to the total mass of the phenol aralkyl resin and the phenol resin.

10. The method for producing a resin fiber according to claim 6 or 7, wherein the fiber diameter of the yarn is 29 μm or more.

11. A carbon fiber obtained by carbonizing the resin fiber according to claim 1 or 2.

12. A method for producing carbon fibers, comprising carbonizing the resin fibers according to claim 1 or 2.

13. Activated carbon fiber obtained by activating the carbon fiber according to claim 11.

14. A method for producing activated carbon fibers, comprising carbonizing and activating the resin fibers according to claim 1 or 2.

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