JP2011074521A - Inorganic particle-containing aromatic polyamide fiber, and method for producing inorganic particle-containing aromatic polyamide dope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inorganic particle-containing aromatic polyamide fiber having excellent flame retardancy, and to provide a method for producing an inorganic particle-containing aromatic polyamide dope usable for the production of the fiber, and having highly superior dispersibility. <P>SOLUTION: The inorganic particle-containing aromatic polyamide fiber has high dispersibility of the inorganic filler and the excellent flame retardancy. The method for producing the inorganic particle-containing aromatic polyamide dope having the highly superior dispersibility and usable for the production of the aromatic polyamide fiber includes forming an aromatic polyamide-inorganic particle slurry by an amide-based solvent containing an inorganic salt and the inorganic particles, and dissolving the aromatic polyamide in the slurry. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an inorganic particle-containing aromatic polyamide fiber having improved flame retardancy obtained using an inorganic particle-containing aromatic polyamide dope, and a method for producing the inorganic particle-containing aromatic polyamide dope.

Conventionally, it is well known that aromatic polyamides produced from aromatic diamines and aromatic dicarboxylic acid dihalides are excellent in heat resistance and flame retardancy. Further, these aromatic polyamides are soluble in amide polar solvents, and they are formed into fibers by a method such as dry spinning, wet spinning, semi-dry semi-wet spinning from a polymer solution in which the aromatic polyamide is dissolved in the solvent. It is also well known to obtain (Patent Documents 1 to 8). This fiber is particularly useful as a heat-resistant and flame-retardant fiber. Emphasis is placed on fields that exhibit these characteristics, such as industrial applications such as filters and electronic parts, and heat resistance, flame resistance, and flame resistance. It is used for disaster prevention and safety clothing such as protective clothing.
Among them, protective clothing is worn in front of high-temperature furnaces such as blast furnaces, electric furnaces, and incinerators, fire-resistant clothing for people engaged in fire fighting work, welding protective clothing for welding work exposed to high-temperature sparks, and ignition. Widely used as flame retardant work clothes for people who handle highly chemicals. In particular, meta-type aromatic polyamide fibers have excellent heat resistance, flame retardancy, and self-extinguishing properties, and general yarn quality is used for clothing fibers, such as natural fibers such as cotton and wool, nylon, polyester, acrylic, etc. Because it is very similar to synthetic fiber, glass fiber, asbestos fiber, phenolic resin fiber, metal foil coating material, etc. that were conventionally used for protective clothing in terms of processability, comfort, washability, and clothing characteristics, etc. It is recognized that it is superior as a protective clothing material.

  However, since these existing fibers have a limit in flame retardancy, there is a limit in the range of fire fighting activities and lifesaving activities. Therefore, if the flame retardancy of conventional protective clothing materials is dramatically improved, for example, in fire fighting activities, regardless of the progress of the fire, it is possible to enter the fire site and perform early fire fighting and rescue activities. Or, even in the heyday fire, it is possible to extinguish the fire early by pouring water close to the fire source. This is expected to bring about benefits such as drastically reducing water loss in fire fighting activities, realizing faster and faster rescue, and improving the safety of firefighters.

  Conventionally, in order to improve the flame retardancy of a resin, a method of adding an organic phosphorus compound, a phosphorus-containing phenol resin, a halogen compound, or the like to a polymer has been proposed. Has been proposed (see Patent Document 9 below). However, since these are low molecular weight organic compounds, some of them are discharged at the time of fiber molding processing, or the problem is contrary to the recent dehalogenation movement that is concerned about environmental problems due to halogen inclusion. Have.

In addition, for the purpose of improving heat resistance and flame retardancy, it is known that fibrous and needle-shaped inorganic fillers are used as flame retardants, thereby improving heat resistance and flame retardancy. For example, a polyamide resin in which magnesium hydroxide and an elastomer are contained in a polyamide resin in an amount of 30% by mass or more and 3 to 20% by mass to improve the flame retardance is disclosed (see Patent Document 10 below).
However, in order to improve the flame retardancy by adding metal hydroxide into the fiber, it must be added in a large amount. As a result, the mechanical properties such as the tensile strength and elastic modulus of the fiber are lowered, and the production stability may be remarkably lowered in the spinning process, and it is always possible to improve the flame retardancy and maintain the mechanical properties. Not necessarily. In addition, in order to effectively exhibit the flame retardancy improving effect without impairing the production stability in the spinning process, it is necessary to highly disperse the filler in the fiber. Although attempts have been made to disperse the filler in the polyamide dope under high shear by mechanical dispersion, etc., a good dispersion state has not been achieved.

Japanese Patent Publication No. 35-14399 Japanese Patent Publication No.47-10863 Japanese Patent Publication No. 48-17551 JP 50-52167 A Japanese Patent Laid-Open No. 56-31209 JP-A-8-074121 JP-A-10-88421 JP 2001-348726 A JP-A-53-122817 Japanese Patent Laid-Open No. 11-1000049

  The present invention has been made in order to solve the problems of the prior art as described above, and one object of the present invention is an inorganic particle-containing aromatic polyamide fiber excellent in flame retardancy without impairing conventional mechanical properties, Is to provide a method for producing an inorganic polyamide-containing aromatic polyamide dope for obtaining the fiber.

The present invention relates to an inorganic particle-containing aromatic polyamide fiber obtained by spinning an inorganic polyamide-containing aromatic polyamide dope, having a limiting oxygen index (LOI value) of 27 or more and satisfying the following formula.
T / To ≧ 0.7
[In the formula, T is the tensile strength of the inorganic polyamide fiber containing inorganic particles, and To is the tensile strength of the comparative fiber made of the same fiber as the fiber except that it does not contain the particles. ]
Here, the aromatic polyamide is preferably copolyparaphenylene • 3,4′-oxydiphenylene terephthalamide.
Examples of the inorganic particles include magnesium hydroxide and / or calcium carbonate.
Furthermore, the content of the inorganic particles is preferably 5 to 20% by mass with respect to the aromatic polyamide.
Next, the present invention relates to an inorganic salt of 30 to 180% by mass of fiber waste (hereinafter also referred to as “aramid fiber waste”) generated in the process of producing aromatic polyamide particles or aromatic polyamide fibers. And an addition step of adding to the amide solvent containing 5 to 20% by mass of inorganic particles based on the polyamide,
A slurrying step of forming an aromatic polyamide-inorganic particle slurry by mixing at a temperature at which the aromatic polyamide particles or the fiber waste is not substantially dissolved,
Next, a melting step of heating to a temperature at which the aromatic polyamide in the slurry is dissolved,
It is related with the manufacturing method of the said inorganic particle containing aromatic polyamide dope provided with these.

  The inorganic particle-containing aromatic polyamide composition (slurry) of the present invention has highly dispersed inorganic particles. For this reason, the polymer dope obtained from the inorganic particle-containing aromatic polyamide composition (slurry) of the present invention also has excellent dispersibility of the inorganic particles, and therefore, the inorganic particle-containing aromatic obtained by spinning from the dope. The polyamide fiber becomes an aromatic polyamide fiber having a highly excellent dispersibility of inorganic particles. For this reason, the inorganic particle containing aromatic polyamide fiber of this invention becomes the thing excellent in the flame retardance, and can provide the various fiber products excellent in the flame retardance. In particular, it is extremely useful for material development for protective clothing applications.

<Inorganic particle-containing aromatic polyamide fiber>
The inorganic particle-containing aromatic polyamide fiber of the present invention has the following specific physical properties. The physical properties and production method of the inorganic polyamide fiber containing inorganic particles of the present invention will be described below.

[Physical properties of inorganic polyamide fibers containing inorganic particles]
[Limited oxygen index (LOI)]
The inorganic particle-containing aromatic polyamide fiber of the present invention has a critical oxygen index of 27 or more as measured in accordance with JIS L1091.
Here, the limiting oxygen index (LOI) is an index indicating the proportion of oxygen necessary for the material to continue to burn, and the larger this value, the higher the flame retardancy.
In order to make the critical oxygen index 27 or more, it is necessary to disperse the inorganic particles in the aromatic polyamide fiber. For example, the inorganic particles include magnesium hydroxide and / or calcium carbonate.
The method for measuring the limiting oxygen index is as described later.

[T / To]
In addition, the aromatic polyamide fiber containing inorganic particles of the present invention has a tensile strength (T) of the fiber, except that it does not contain inorganic particles, and the tensile strength of the comparative fiber made of the same fiber as the above-mentioned fibers. The ratio (T / To) to (To) is 0.7 or more, preferably 0.8 or more. If the ratio is less than 0.7, high strength is lost. In order to make this ratio 0.7 or more, it is necessary to reduce the dispersed particle diameter of the inorganic particles dispersed in the fiber. For example, the dispersed particle average equivalent diameter of the inorganic particles dispersed in the fiber may be 0.5 μm or less, preferably 0.4 μm.

[Single yarn fineness]
The single yarn fineness of the inorganic particle-containing aromatic polyamide fiber of the present invention is preferably 0.5 to 50 dtex. If it is less than 0.5 dtex, the added particles may act as yarn defects, and the spinning property may become unstable. Moreover, since the specific surface area of the fiber is increased, it is susceptible to light resistance degradation. On the other hand, when it exceeds 50 dtex, the specific surface area of the fiber becomes small and is not easily subjected to light resistance deterioration. On the other hand, since the specific surface area is small in the spinning process, coagulation tends to be incomplete, and as a result, the process condition tends to be disturbed in the spinning and drawing processes, and the physical properties are also likely to be lowered.

[Strength]
In addition, the inorganic particle-containing aromatic polyamide fiber of the present invention has a higher strength, but the strength tends to decrease as the concentration of the inorganic particles is increased, and is preferably 10 cN / dtex or more. If it is less than 10 cN / dtex, the characteristics as a high-strength fiber are insufficient. More preferably, it is 15 cN / dtex or more. The tensile strength of the fiber can be controlled to 10 cN / dtex or more by controlling, for example, the draw ratio and the proportion of inorganic particles to be dispersed with respect to the polymer component in the fiber.

[Elongation]
Furthermore, the elongation of the inorganic particle-containing aromatic polyamide fiber of the present invention is preferably 3.0% or more. If it is less than 3.0%, the twist strain increases when the yarn is used as a twisted yarn, and the strength utilization rate of the twisted cord is lowered. Therefore, in the case of a rope or net for outdoor use where light resistance is particularly required, high strength durability becomes a problem. The elongation is more preferably 3.5 to 5.0%.

<Material used for inorganic polyamide-containing aromatic polyamide dope of the present invention>
[Aromatic polyamide]
The aromatic polyamide in the present invention can be obtained from low-temperature solution polymerization or interfacial polymerization of dicarboxylic acid dichloride (hereinafter also referred to as “acid chloride”) and diamine in a solution.
Examples of the diamine component used in the present invention include p-phenylenediamine, 2-chloro p-phenylenediamine, 2,5-dichloro p-phenylenediamine, 2,6-dichloro p-phenylenediamine, m-phenylenediamine, 3 , 4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, etc. However, it is not limited to these.
Among them, as the diamine component, p-phenylenediamine, m-phenylenediamine and 3,4'-diaminodiphenyl ether can be used singly or in combination.

  Specific examples of the acid chloride used in the present invention include isophthalic acid chloride, terephthalic acid chloride, 2-chloroterephthalic acid chloride, 2,5-dichloroterephthalic acid chloride, and 2,6-dichloroterephthalic acid. Examples include, but are not limited to, chloride and 2,6-naphthalenedicarboxylic acid chloride. Among these, terephthalic acid dichloride and isophthalic acid dichloride are preferable as the acid chloride. Accordingly, examples of the aromatic polyamide in the present invention include copolyparaphenylene 3,4'-oxydiphenylene terephthalamide, polyparaphenylene terephthalamide, and polymetaphenylene terephthalamide.

Specific solvents for polymerizing aromatic polyamides include organic polar amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone and N-methylcaprolactam, tetrahydrofuran And water-soluble ether compounds such as dioxane, water-soluble alcohol compounds such as methanol, ethanol and ethylene glycol, water-soluble ketone compounds such as acetone and methyl ethyl ketone, and water-soluble nitrile compounds such as acetonitrile and propionitrile. These solvents can be used as a mixed solvent of two or more kinds, and are not particularly limited. The solvent is preferably dehydrated.
In this case, in order to increase solubility, an appropriate amount of a generally known inorganic salt may be added before, during or after the polymerization. Examples of such inorganic salts include lithium chloride and calcium chloride.

Moreover, when manufacturing aromatic polyamide, these diamine and acid chloride are preferably used in a molar ratio of diamine to acid chloride of 0.90 to 1.10, more preferably 0.95 to 1.05. Is preferred.
The ends of this aromatic polyamide can also be sealed. In the case of sealing with an end-capping agent, examples of the end-capping agent include phthalic acid chloride and substituted products thereof, and examples of the amine component include aniline and substituted products thereof.
In the reaction of a generally used acid chloride and diamine, an aliphatic or aromatic amine or a quaternary ammonium salt can be used in combination in order to capture an acid such as hydrogen chloride formed.
After completion of the reaction, a basic inorganic compound such as sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide or the like is added as necessary to carry out a neutralization reaction.

The reaction conditions do not require special restrictions. The reaction between acid chloride and diamine is generally rapid, and the reaction temperature is, for example, -25 ° C to 100 ° C, preferably -10 ° C to 80 ° C.
The aromatic polyamide thus obtained can be put into a non-solvent such as alcohol or water, precipitated, and taken out as a pulp. This can be dissolved again in another solvent and used for molding, but the solution obtained by the polymerization reaction can be used as it is as a molding solution. The solvent used for re-dissolving is not particularly limited as long as it dissolves the aromatic polyamide, but a solvent used for the polymerization of the aromatic polyamide is preferable.

[Aromatic polyamide particles]
The aromatic polyamide particles used in the present invention can be produced according to a conventionally known method. Specifically, for example, an aromatic polyamide solution is obtained by reacting an aromatic dicarboxylic acid chloride with an aromatic diamine in an amide solvent.
Subsequently, the aromatic polyamide particles used in the present invention can be produced from the obtained aromatic polyamide solution. Specifically, for example, the aromatic polyamide particles can be obtained by reprecipitation and purification of the aromatic polyamide by dropping the obtained aromatic polyamide solution into water.

The average particle size of the aromatic polyamide particles used in the present invention is preferably from 0.1 μm to 500 μm, and more preferably from 0.5 μm to 100 μm. Particles having an average particle size of less than 0.1 μm are not preferable because they are difficult to produce and the productivity and economy are reduced.
Here, the average particle diameter is a measured value obtained when a dry powder was evaluated by a laser diffraction / scattering method (Microtrac method) with Nikkiso Co., Ltd. Microtrac MT3200II.

[Aramid fiber waste]
The aromatic polyamide fiber used for the aramid fiber waste may be one produced by a known production method. For example, an aromatic polyamide dope for spinning is extruded into a coagulation liquid by a semi-dry semi-wet spinning method, taken as a coagulated thread from the coagulation liquid, the solvent is sufficiently removed in a water washing process, and moisture is dried in a drying process. Thereafter, it is produced by heat treatment or hot drawing.

Further, the aramid fiber waste used as a raw material in the method of the present invention is a fiber waste generated at the production site of the aromatic polyamide fiber as described above, and is generated at the start of winding, paper tube replacement, product change, or trouble occurrence. .
As the aramid fiber waste in the present invention, unstretched fiber waste is particularly preferably used among the fiber waste generated in the process of producing the aromatic polyamide fiber. Unstretched fiber waste is fiber waste generated before the step of performing heat drawing or heat treatment, and this fiber waste is advantageously used because it easily forms a slurry described later.
The single yarn fineness of the aramid fiber waste is preferably 200 dtex or less, and the fiber length is preferably about 10 to 100 mm.

  The above aromatic polyamide particles and aramid fiber waste can be used alone or in combination.

[Inorganic salt]
Next, the inorganic salt used in the present invention is used to improve solubility when kneading and dissolving a mixture of aromatic polyamide particles and / or aromatic polyamide fiber waste and an amide solvent. Examples of such inorganic salts include, but are not limited to, calcium chloride, lithium chloride, lithium carbonate and the like. The amount of the inorganic salt is in the range of 30 to 180% by mass, preferably 50 to 100% by mass with respect to the polyamide comprising aromatic polyamide particles or aromatic polyamide fiber waste. When the amount of the inorganic salt is less than 30% by mass, the solubility of the aromatic polyamide fiber scraps or polymer particles in the amide solvent is not preferable. On the other hand, when it exceeds 180% by mass, it is difficult to completely dissolve the inorganic salt in the amide solvent, which is not preferable.

[Inorganic particles]
Next, as the inorganic particles used in the present invention, for example, magnesium hydroxide and calcium carbonate can be used. At that time, it was confirmed that the flame retardancy was improved even if the amount of inorganic particles added to the fiber was small. For this reason, the compounding quantity of the inorganic particle with respect to a fiber can be reduced, maintaining a high flame retardance. Therefore, it is possible to provide a flame retardant fiber capable of imparting high flame retardancy with a small blending amount without impairing the mechanical properties of the fiber. Further, as other inorganic particles, for example, an inorganic particle flame retardant such as aluminum hydroxide can be used.

As mentioned above, the compounding quantity to the fiber of the inorganic particle of this invention demonstrated is 1-20 mass% with respect to the polyamide which consists of an aromatic polyamide particle or an aramid fiber waste, Preferably it is 5-10 mass%, such Flame retardancy can be imparted to the fiber with a small amount. If it is less than 1% by mass, the predetermined flame retardancy improving effect is not exhibited. On the other hand, if it exceeds 20% by mass, the moldability of the fiber becomes poor, which is not preferable.
In addition, the compounding quantity of the particle | grains to the fiber can also be 30-50 mass%. In this case, the mechanical strength of the fiber is somewhat sacrificed, but the flame retardancy can be greatly improved.

In addition, the inorganic particles are formed by subjecting a surface treatment layer that has been surface treated with a silane coupling agent or a titanium coupling agent, preferably a coupling agent such as a silane coupling agent, or a surface treatment agent such as a surfactant. Furthermore, it is preferable to have it.
This surface treatment agent is present on the surface of the coating layer and forms a surface treatment layer. Thus, by appropriately selecting the type of the surface treatment agent, the surface state of the surface treatment layer of the inorganic particles is adjusted, the affinity with the polymer is improved, and the dispersibility of the inorganic particles in the polymer is improved. Thus, high flame retardancy can be imparted with a small amount of blending.

Here, examples of the silane coupling agent include silane coupling represented by the following formula (I).
^{_{(R 1) n -Si-X}} (4-n) (I)
(R ¹ is an organic group having ^{1 to} 300 carbon atoms and may include heteroatoms such as N, O, S, and halogen. X: an alkoxyl group such as OR ² or a halogen atom, and R ² is a C number. 1 to 18 organic groups.)
Specific examples of R ¹ include aliphatic groups such as ethyl group, propyl group, isopropyl group, butyl group, pentyl group, and hexyl group, alicyclic groups such as cyclohexyl group, and aromatic groups such as phenyl group, toluyl group, and naphthyl group. Group. In addition, these may contain heteroatoms such as N, O, S and halogen, and in this case, amino group, chloro group, bromo group, cyano group, acid anhydride, epoxy group, mercapto group and the like can be mentioned. Examples of R ² of OR ² contained in X include a methyl group, an ethyl group, and a propyl group.

Specific examples of the silane coupling agent represented by the formula (I) include, for example, methyltrimethoxysilane, methyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n- Butyltrimethoxysilane, n-butyltriethoxysilane, n-pentyltrimethoxysilane, n-pentyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, Naphthyltrimethoxysilane, toluyltrimethoxysilane, toluyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyl Triethoxysilane, 3-aminopropyldimethylethoxysilane, 3-aminopropylmethyldiethoxysilane, p-aminophenyltrimethoxysilane, P-aminophenyltriethoxysilane, 3-cyanoethylmethyldimethoxysilane, 3-cyanoethyltrimethoxysilane 3-cyanomethyltrimethoxysilane, 3-cyanopropyltrimethoxysilane, 3-cyanopropyltriethoxysilane, 3- (triethoxysilyl) propylsuccinic anhydride, 2- (3,4, -epoxycyclohexyl) Ethyltriethoxysilane, 2,3,4-epoxycyclohexyl) ethyltrimethoxysilane, 5,6-epoxyhexyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxy Silane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-bromopropyltrimethoxysilane, 3-bromopropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate mono Sulfide, 3-mercaptopropyldimethoxymethylsilane, 3-nitropropyldimethoxymethylsilane, 3-chloropropyldimethoxymethylsilane, 11-bromoundecyltri Examples include silane coupling agents such as toxisilane, 11-bromoundecyltrichlorosilane, 11-bromoundecyldimethylchlorosilane, and imidazolesilane described in paragraphs “0079” to “0085” of JP-A-2006-124698. be able to.
Of these silane coupling agents, epoxy silane, amino silane, imidazole silane, and alkoxy silane are preferred.
These silane coupling agents can be used alone or in combination of two or more.

  The silane coupling agent can make the dispersibility of the inorganic particles extremely good. Therefore, high flame retardancy can be imparted to the resulting fiber with a small amount of inorganic particles.

  As the surfactant, an ionic surfactant, a nonionic surfactant, or the like can be used. Here, as the ionic surfactant, anionic surfactants such as fatty acids and phosphoric acids, cationic surfactants such as ammonium surfactants, carboxylic acids and phosphate esters, etc. Ionic surfactants can be used, and nonionic surfactants such as carboxylic acids and phosphate esters can be used.

  In addition, in this invention, fillers other than the inorganic particle of this invention can be used together in the range which does not impair a physical property. Examples of the filler used include non-fibrous fillers such as fibrous or plate-like, scale-like, granular, indeterminate, and crushed products. Specific examples include glass fibers, PAN-based and pitch-based carbon fibers. , Stainless steel fiber, metal fiber such as aluminum fiber and brass fiber, organic fiber such as aromatic polyamide fiber, gypsum fiber, ceramic fiber, zirconia fiber, alumina fiber, silica fiber, titanium dioxide fiber, silicon carbide fiber, rock wool, titanium Potassium oxide whisker, barium titanate whisker, aluminum borate whisker, silicon nitride whisker, mica, layered clay mineral, talc, kaolin, silica, calcium carbonate, glass beads, glass flakes, glass microballoon, clay, molybdenum disulfide, wollastonite , Titanium dioxide, suboxide , Calcium polyphosphate, graphite, metal powders, metal flakes, metal ribbons, metal oxides, carbon powder, graphite, carbon flake, such flake carbon. Moreover, the said filler can also be used in combination of 2 or more types.

  The filler used in the present invention can be used by treating the surface thereof with a known coupling agent (for example, silane coupling agent, titanate coupling agent, etc.) or other surface treatment agents. .

[Amide solvent]
Further, the amide solvent used in preparing the inorganic polyamide-containing aromatic polyamide dope of the present invention is N, N-dimethylformamide, N, N-dimethylacetamide used for polymerizing the aromatic polyamide of the present invention, Examples thereof include organic polar amide solvents such as N-methyl-2-pyrrolidone and N-methylcaprolactam.
The amount of the amide solvent used is such that the resulting polyamide dope has a polymer concentration of 1 to 10% by mass, preferably 4 to 6% by mass.

<Method for producing inorganic polyamide-containing aromatic polyamide dope>
Next, the specific example of the manufacturing method of the inorganic particle containing aromatic polyamide dope of this invention and the manufacturing method of the aromatic polyamide fiber of this invention using this dope is shown below.
In the present invention, first, in the first addition step, aromatic polyamide particles or aramid fiber scraps are added to 30 to 180% by mass of inorganic salt with respect to the polyamide and 5 to 20% by mass of inorganic particles with respect to the polyamide. Add to the amide-based solvent contained to obtain a mixture.
In the present invention, in the second slurrying step, the mixture is then mixed at a temperature at which the aromatic polyamide particles or the aramid fiber scraps are not substantially dissolved in the amide solvent, so that the aromatic polyamide fiber scraps (aromatic Group polyamide particles) must be in a slurry state. The slurry state in the present invention is a state in which fine aromatic polyamide fiber scraps (aromatic polyamide particles) of several microns to several thousand microns are dispersed in an amide solvent.

  In the present invention, the “substantially insoluble temperature” differs depending on the type of amide solvent, the type and amount of the inorganic salt, and also varies depending on the fineness of the aromatic polyamide fiber waste and the average particle size of the aromatic polyamide particles. However, in the present invention, the “substantially non-melting temperature” refers to the temperature when the fiber waste (polyamide particles) is immersed in an amide solvent for 1 hour and the mass reduction rate is 0.1% or less. It is defined as a temperature that does not substantially dissolve. In the present invention, this temperature is preferably in the range of 15 to 40 ° C. If the temperature at this time exceeds 40 ° C., dissolution of aramid fiber waste (aromatic polyamide particles) proceeds, and agglomerates of aramid fiber waste (aromatic polyamide particles) are generated. It takes time to dissolve and the aggregate tends to remain as an undissolved product. Therefore, the slurrying temperature is preferably in the range of 15 to 40 ° C. When this temperature is less than 15 ° C., it takes a long time to make a slurry, which is not industrially preferable.

  In general, when dissolving fiber waste, etc., it is preliminarily finely pulverized with a shredder or the like for the purpose of enhancing the dissolution effect in a solvent. In the present invention, aramid fiber waste or fragrance is used. The slurry of the group polyamide particles makes it possible to obtain fine aramid fiber scraps or a state in which the aromatic polyamide particles are dispersed in the amide solvent, so that it is not necessary to finely pulverize with a shredder or the like in advance, and Since the time required for the dope preparation can be greatly shortened, it is industrially preferable. This slurry is stable in the above temperature range, and can be stored or transported as the slurry in this temperature range.

  According to the method of the present invention, thereafter, in the third melting step, the aromatic polyamide slurry is heated to a temperature range in which the aromatic polyamide fiber waste (aromatic polyamide particles) is dissolved and kneaded under high shear stress. As a result, an aromatic polyamide dope can be obtained. This temperature is preferably high from the viewpoint of enhancing the solubility of the aromatic polyamide fiber waste (aromatic polyamide particles), but is 130 ° C. or less, particularly 50 ° C. in view of avoiding thermal degradation / decomposition of the amide solvent. It is preferably 120 ° C. or lower.

In the present invention, a method in which aromatic polyamide particles or aramid fiber waste and an amide solvent are mixed and the mixture is kneaded under high shear stress has particularly good solubility and is industrially preferable.
The kneading apparatus used in the present invention is not particularly limited as long as it can perform shear kneading, and includes a screw type extruder such as a single screw extruder and a twin screw extruder, a Banbury mixer, a planetary mixer, a roller, a kneader, and the like. Can be mentioned.
The aromatic polyamide dope thus obtained can be purified by subjecting the insoluble matter to filtration, decolorization and the like.

  The aromatic polyamide dope obtained by the present invention is adjusted to an appropriate concentration as it is or by adding a homogeneous aromatic polyamide dope polymer to the same or by diluting with the same amide solvent. Can be used.

  In addition, the intrinsic viscosity (IV) of the aromatic polyamide dope obtained by the present invention is 2.0 to 4.0. The intrinsic viscosity is a value measured at 30 ° C. for a solution having a polymer concentration of 0.5 g / dl in 98% concentrated sulfuric acid.

<Method for producing inorganic polyamide fiber containing aromatic polyamide>
The method for producing the inorganic particle-containing aromatic polyamide fiber of the present invention is not particularly limited as long as the inorganic particle-containing aromatic polyamide dope of the present invention is used as a raw material, and a known spinning method is adopted. Can do. Any of wet spinning, dry spinning, and semi-dry semi-wet spinning can be adopted. Since the inorganic particle-containing aromatic polyamide composition of the present invention has a very high melting point, the dope is dissolved by dissolving in a solvent. And then spinning from the dope.

That is, the yarn is produced using the aromatic polyamide dope of the present invention containing inorganic particles.
First, the polymer dope is discharged from the spinneret. The hole diameter, nozzle length, number of holes, material, and the like of the spinneret used for discharging are not particularly limited, and can be appropriately adjusted in consideration of the fiber diameter, the number of single yarns, the spinnability, and the like of the obtained fiber. .
The temperature of the polymer dope when passing through the spinneret and the temperature of the spinneret are not particularly limited because they can be appropriately adjusted depending on the concentration and viscosity of the polymer dope to be used. Considering discharge pressure, polymer dope deterioration, and the like, 75 to 120 ° C. is preferable.

  In addition, in this invention, the density | concentration with respect to the amide-type solvent of the polymer which consists of aromatic polyamide particle | grains or aromatic polyamide fiber waste becomes like this. Preferably it is 0.5-30 mass%, More preferably, it is 1-10 mass%. When the polymer concentration is less than 0.5% by mass, the polymer has little entanglement and the viscosity necessary for spinning cannot be obtained. On the other hand, if the polymer concentration exceeds 30% by mass, unstable flow tends to occur when discharging from the nozzle, making it difficult to spin stably.

  Next, the polymer dope discharged from the spinneret is solidified in a coagulating liquid. At this time, when the temperatures of the spinneret and the coagulating liquid are greatly different, when the spinneret and the coagulating liquid come into contact with each other, the respective temperatures change and control becomes difficult, so that an air gap can be provided. The length of the air gap at this time is not particularly limited, but is preferably 5 to 15 mm from the viewpoints of single yarn adhesion, temperature controllability, stringiness, and the like. The coagulation liquid used here is an aqueous solution of an amide solvent used for polymer dope, and its temperature and solvent concentration are not particularly limited. As long as there is no problem with the above, it can be adjusted as appropriate.

  The coagulation bath uses a poor solvent for aromatic polyamide, but usually a good solvent is added to increase the coagulation rate so that the aromatic polyamide dope solvent quickly escapes and the aromatic polyamide fiber is not defective. Adjust. In general, it is preferable to use water as the poor solvent and an aromatic polyamide dope solvent as the good solvent. The ratio of good solvent / poor solvent is generally preferably 15/85 to 40/60, although it depends on the solubility and coagulability of the aromatic polyamide.

  Next, the solidified yarn is washed with water. The purpose of this washing step is to remove as much of the amide solvent in the yarn as possible using water. The washing conditions are not particularly limited, and the number of washing baths, the temperature, and the like can be appropriately adjusted as long as NMP in the yarn can be sufficiently removed.

  Next, the washed fiber is dried. The drying conditions at this time are not particularly limited, and there is no problem as long as moisture contained in the fibers can be sufficiently removed. However, in consideration of workability and deterioration of the fibers due to heat, the temperature is 150 to 250 ° C. preferable. For drying, either a contact-type drying apparatus such as a roller or a non-contact type drying apparatus in which fibers pass through a drying furnace can be used.

  Since the obtained fiber is not sufficiently oriented at this stage, the crystal orientation degree determined by wide-angle X-ray diffraction after hot drawing is 89% or more, and the degree of crystallinity is 74% or more. And it is preferably crystallized. Accordingly, when either or both of the crystal orientation degree and the crystallinity degree are low, the mechanical properties of the resulting fiber are likely to be insufficient even when heat (stretching) treatment is performed.

  That is, the dried fiber is hot-drawn. In this step, the object is to highly orient polymer molecules in the fiber and impart strength by hot drawing of the fiber. The thermal stretching temperature at this time is not particularly limited as long as sufficient stretching and strength are exhibited, but is preferably 300 to 600 ° C, more preferably 320 ° C to 580 ° C, and most preferably 350 to 550. ° C. The draw ratio in this hot drawing step is preferably 5 to 15 times, but is not particularly limited to this range as long as sufficient high strength can be achieved. Moreover, in this thermal stretching process, there is no particular problem even if it is performed in multiple stages as necessary. An apparatus used for heat-drawing the fiber includes a contact-type hot plate and a non-contact type furnace, but is not particularly limited. The temperature of the fiber is raised to a predetermined temperature, and a predetermined magnification is used. Any apparatus can be used as long as it can be stretched.

  Then, if necessary, an oil agent is applied for the purpose of imparting charge suppression or lubricity to the fiber, and finally wound with a winder. There are no particular limitations on the type of oil agent to be applied and the amount to be applied, and the oil agent can be appropriately adjusted in consideration of the use of the fiber and the handleability of the fiber. Moreover, about the winding method with a winder, it can wind by adjusting winding conditions, such as tension | tensile_strength and contact pressure, suitably using a well-known winder.

<Use of inorganic particle-containing aromatic polyamide fiber>
The inorganic particle-containing aromatic polyamide fibers of the present invention thus obtained constitute fiber structures such as braids, ropes, twisted cords, yarns, and cotton, in addition to fabrics such as woven fabrics, knitted fabrics, and nonwoven fabrics.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, these Examples and Comparative Examples are for helping understanding of the present invention, and the scope of the present invention is not limited by these descriptions.
In addition, each characteristic value in an Example was measured with the following method.

<Fineness>
It measured according to JIS-L-1015.
<Tensile strength of fiber>
Using a tensile tester (Orientec Co., Ltd., trade name: Tensilon universal tester, model: RTC-1210A), based on the procedure of ASTM D885, the measurement sample length is 500 mm, the chuck tensile speed is 250 mm / min, the initial load is 0. Measurement was performed under the condition of 2 cN / dtex.

<Limit oxygen index LOI value>
The limiting oxygen index was measured by a measuring method based on the JIS L 1091 E method.
(Measurement condition)
Specimen classification: No. E-2 Fabric creation method: Circular knitted fabric (23 wales / inch, 18 courses / inch)
Type of igniter heat source: JIS K2240 Type 1 No. 1 (LP gas)
The critical oxygen index is determined earlier in the following (a) or (b). (A) Combustion length when determining the critical oxygen index: 50 mm
(B) Combustion time when determining the critical oxygen index: 180 seconds <Fineness>
It measured according to JIS-L-1015.

<T / To>
T / To was determined as the ratio of the tensile strength (T) of the fiber to the tensile strength (To) of the comparative fiber made of the same fiber as the fiber except that the composite particle was not contained.

<Dispersibility (Dispersed particle average equivalent diameter of inorganic particles in fiber)>
When the fiber is cut and the cross section is observed with an electron microscope at a magnification of 100,000, the average particle dispersion area S (μm ² ) per observation cross section of 25 μm ² is calculated by the following formula (Y): The dispersion average equivalent diameter was used.
Y (μm) = 2 × √ (S / π)

<Aromatic polyamide fiber scrap>
In a stirring vessel in which nitrogen is flowing inside, N-methyl-2-pyrrolidone (NMP) is weighed and dissolved so that paraphenylenediamine and 3,4'-diaminodiphenyl ether are equimolar. It was. To this diamine solution, terephthalic acid dichloride was weighed and added in an amount approximately equal to the total molar amount of diamine. After completion of the reaction, the reaction mixture was neutralized with calcium hydroxide to obtain an aromatic polyamide dope. The dope is discharged from a spinneret having a hole diameter of 0.3 mm and a hole number of 100 holes, and after being spun and solidified in an aqueous solution having an NMP concentration of 30% by mass through an air gap of about 10 mm (semi-dry semi-wet spinning method) , Washed with water, dried, then stretched 10 times at a temperature of 500 ° C., and then wound up to obtain an aromatic polyamide fiber (copolyparaphenylene 3.4′-oxydi) having a single yarn fineness of 1.67 dtex. Phenylene terephthalamide fiber).
As the aromatic polyamide fiber waste, unstretched fiber waste having an intrinsic viscosity (IV) of 3.5 generated by yarn breakage in the drawing step was used. The average fiber length of the fiber waste is about 20 to 50 mm.

<Aromatic polyamide dope production method>
Inorganic particles were dispersed in N-methyl-2-pyrrolidone (NMP) using a bead mill (Nano Grain Mill, manufactured by Iwata Tekko Co., Ltd.). At this time, 0.3 mm zirconia beads were used as media.
The fiber waste was added to the NMP / calcium chloride / inorganic particle dispersion to a predetermined amount and stirred at 25 ° C. for 30 minutes to obtain an amide solvent slurry of fiber waste. The slurry was heated and kneaded at 60 ° C. using a planetary mixer (product name PVM-5) manufactured by Iwata Tekko Co., Ltd. to obtain a transparent aromatic polyamide dope.

<Aromatic polyamide fiber manufacturing method>
After the dope is discharged from a spinneret having a hole diameter of 0.3 mm and a hole number of 100 holes, and spun into an aqueous solution with an NMP concentration of 30% by mass through an air gap of about 10 mm, it is solidified (semi-dry semi-wet spinning method) Then, it was washed with water, dried, then stretched 10 times at a temperature of 500 ° C., and then wound up.

Example 1
Magnesium hydroxide fine particles (MG-23D manufactured by Kyoritsu Material Co., Ltd.) were used as inorganic particles to obtain 10% by mass added copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers. Table 1 shows the results of evaluating the obtained fibers.

Example 2
As inorganic particles, fine particles of magnesium hydroxide were used to obtain 20% by mass added copolyparaphenylene 3,4'-oxydiphenylene terephthalamide fibers. Table 1 shows the results of evaluating the obtained fibers.

Example 3
Magnesium hydroxide fine particles were used as the inorganic particles to obtain 5% by mass added copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fiber. Table 1 shows the results of evaluating the obtained fibers.

Example 4
Calcium carbonate fine particles (CS · 3N-A manufactured by Ube Materials Co., Ltd.) were used as inorganic particles to obtain 10% by mass added copolyparaphenylene · 3,4′-oxydiphenylene terephthalamide fiber. Table 1 shows the results of evaluating the obtained fibers.

Comparative Example 1
A fiber of copolyparaphenylene 3,4'-oxydiphenylene terephthalamide without addition of inorganic particles was obtained. Table 1 shows the results of evaluating the obtained fibers.

Comparative Example 2
Magnesium hydroxide fine particles were used as the inorganic particles to obtain 30% by mass added copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fiber. Table 1 shows the results of evaluating the obtained fibers.

Comparative Example 3
Magnesium hydroxide fine particles were used as inorganic particles to obtain 1% by mass of copolyparaphenylene-3, '4-oxydiphenylene terephthalamide fiber. Table 2 shows the results of evaluating the obtained fibers.

Comparative Example 4
Copolyparaphenylene 3,4'-oxydidioxide is added in an amount of 10 mass% in the same manner except that magnesium hydroxide fine particles are dispersed in NMP and then blended into the aromatic polyamide dope. A phenylene terephthalamide fiber was obtained.
In dispersing the fine particles of magnesium hydroxide in NMP, a bead mill (trade name: Nano Grain Mill, manufactured by Iwata Tekko Co., Ltd.) was used, and 0.3 mm zirconia beads were used as the media. The blending with the aromatic polyamide dope was carried out using a planetary mixer (product name PVM-5) manufactured by Iwata Iron Works. Table 2 shows the results of evaluating the obtained fibers.

Comparative Example 5
A fiber of copolyparaphenylene 3,4'-oxydiphenylene terephthalamide added at 10% by mass in the same manner as in Example 1 except that magnesium hydroxide fine particles were directly added to the aromatic polyamide dope. It was.
In addition, in blending the magnesium hydroxide fine particles into the aromatic polyamide dope, a planetary mixer (product name: PVM-5) manufactured by Iwata Tekko Co., Ltd. was used. Table 2 shows the results of evaluating the obtained fibers.

  The inorganic particle-containing aromatic polyamide fiber according to the present invention can provide a fiber product having excellent flame retardancy, and is particularly useful as a material for use in protective clothing.

Claims (6)

An inorganic particle-containing aromatic polyamide fiber obtained by spinning an inorganic polyamide-containing aromatic polyamide dope, having a limiting oxygen index (LOI value) of 27 or more and satisfying the following formula:
T / To ≧ 0.7
[In the formula, T is the tensile strength of the inorganic polyamide fiber containing inorganic particles, and To is the tensile strength of the comparative fiber made of the same fiber as the fiber except that it does not contain the particles. ]   The inorganic particle-containing aromatic polyamide fiber according to claim 1, wherein the aromatic polyamide is copolyparaphenylene 3,4'-oxydiphenylene terephthalamide.   3. The inorganic particle-containing aromatic polyamide fiber according to claim 1, wherein the inorganic particle is magnesium hydroxide and / or calcium carbonate.   The inorganic particle-containing aromatic polyamide fiber according to any one of claims 1 to 3, wherein the content of the inorganic particles is 5 to 20% by mass with respect to the aromatic polyamide. An amide containing 30 to 180% by mass of inorganic salt with respect to the polyamide and 5 to 20% by mass of inorganic particles with respect to the polyamide, including aromatic polyamide particles or fiber waste generated in the process of producing aromatic polyamide fibers An addition step to be added to the system solvent,
A slurrying step of forming an aromatic polyamide-inorganic particle slurry by mixing at a temperature at which the aromatic polyamide particles or the fiber waste is not substantially dissolved,
Next, a melting step of heating to a temperature at which the aromatic polyamide in the slurry is dissolved,
The method for producing an inorganic polyamide-containing aromatic polyamide dope according to claim 1, comprising:   The method for producing an inorganic polyamide-containing aromatic polyamide dope according to claim 5, wherein the mixing in the slurrying step is carried out under high shear stress.