JP2011046814A - Thin layer sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin layer sheet with higher quality containing pyridobisimidazole fibers as a reinforcing material. <P>SOLUTION: The thin layer contains a pyridobisimidazole fiber with root mean square roughness of the fiber surface of 30 nm or less and a resin. Gaps among fibers can be further reduced when fibers are aligned in uniaxial direction if the root mean square roughness of the fiber surface is small, that is, the fiber surface is smooth. Therefore, the thin sheet with higher quality is obtained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thin sheet containing pyridobisimidazole fiber as a reinforcing material.

  As fibers having high strength and high heat resistance, pyridobisimidazole fibers, polybenzazole fibers made of polybenzoxazole, polybenzothiazole, and the like are known. For such fibers, for example, pyridobisimidazole fibers containing a specific repeating group (see Patent Document 1 (Claim 14)); polybenzazole fibers and pyridobisimidazole fibers having a specific crystal presence state (See Patent Document 2 (Claims 1 and 6)).

  Pyridobisimidazole fiber has the highest level of performance among organic fibers in all respects in terms of strength, elastic modulus, heat resistance, flame retardancy, and has been developed for various applications that take advantage of these characteristics. ing. Here, generally, when a product is processed using a pyridobisimidazole fiber as a composite material together with a resin or the like, a method such as filament winding is employed. However, such a method has a problem that it takes a long time to manufacture a product. Therefore, from the viewpoint of improving the workability of the composite material, a thin layer sheet in which a plurality of pyridobisimidazole fibers are arranged in a sheet and impregnated with a resin and semi-cured is desired.

JP-T 8-509516 International Publication No. 2008/023719

  When forming the thin layer sheet as described above, in order to exhibit the excellent heat resistance and flame retardancy of the pyridobisimidazole fiber, it is preferable to align the fibers in a uniaxial direction without gaps. However, conventional pyridobisimidazole fibers have a rough surface and are not smooth, so it is difficult to arrange them without gaps. Therefore, the conventional thin layer sheet using pyridobisimidazole fibers has a large gap between the fibers and has insufficient quality.

  This invention is made | formed in view of the said situation, It is a thin layer sheet containing a pyridobisimidazole fiber as a reinforcing material, Comprising: It aims at providing a high quality thin layer sheet.

  The thin-layer sheet of the present invention that has been able to solve the above-mentioned problems contains pyridobisimidazole fibers having a mean square roughness of the fiber surface of 30 nm or less and a resin. If the mean square roughness of the fiber surface is small, that is, if the fiber surface is smooth, the gaps between the fibers can be further reduced when the fibers are aligned in a uniaxial direction. Therefore, the thin layer sheet of the present invention has high quality with reduced gaps between pyridobisimidazole fibers.

  The pyridobisimidazole fiber preferably has a number of reciprocating wear at break of 4000 times or more in a wear strength test measured according to JIS L1095 (1999) -9.10.2B. The thickness of the thin layer sheet of the present invention is preferably 5 μm or more and 100 μm or less.

  The pyridobisimidazole fiber is a spinning step in which a spinning dope containing a pyridobisimidazole polymer and polyphosphoric acid is spun from a spinneret; What was manufactured through the coagulation | solidification process of immersing in the phosphoric acid aqueous solution of 80 mass% or less above and coagulating a pyridobisimidazole polymer is preferable. In this case, the temperature of the phosphoric acid aqueous solution in the coagulation step is preferably −30 ° C. or more and 5 ° C. or less.

  According to the present invention, a thin layer sheet containing pyridobisimidazole fiber as a reinforcing material, and a thin layer sheet with higher quality can be obtained.

1. Thin layer sheet The thin layer sheet of the present invention comprises pyridobisimidazole fiber having a mean square roughness of the fiber surface of 30 nm or less and a resin.

  The thin layer sheet of the present invention is a sheet-like material obtained by impregnating the pyridobisimidazole fiber with a resin. Specifically, for example, a sheet-like material containing a fiber bundle and a thermoplastic resin; And a thermosetting resin composition, and a sheet-like material obtained by curing the curable resin up to the B stage. In addition, in the case where a thermosetting resin is used as the curable resin composition, for example, the B stage indicates an intermediate curing state of the thermosetting resin, and the resin in this state is softened when heated. Swells when in contact with a seed solvent, but does not melt or dissolve completely.

  As an aspect of a thin layer sheet, for example, (I) an aspect in which a pyridobisimidazole fiber bundle is impregnated with a resin in a fiber layer oriented in a certain direction; (II) from a pyridobisimidazole fiber bundle A mode in which a woven fabric is impregnated with a resin; (III) a mode in which pyridobisimidazole fibers are dispersed in the form of a single fiber, spun yarn, chopped fiber, staple fiber, or the like in the resin; Is mentioned. Among these, the above embodiment (I) or (II) is preferable.

  The thickness of the thin layer sheet of the present invention is preferably 5 μm or more, more preferably 8 μm or more, further preferably 10 μm, preferably 100 μm or less, more preferably 60 μm or less, and further preferably 40 μm or less. When the thickness of the thin layer sheet exceeds 100 μm, the flexibility of the thin layer sheet is lost, so that the fiber does not play a role as a reinforcing agent. On the other hand, in order to make the thickness less than 5 μm, it is necessary to apply an excessive pressure to the thin layer sheet, and there is a possibility that the fiber is broken at this time.

2. Pyridobisimidazole fiber The pyridobisimidazole fiber used in the present invention will be described. The pyridobisimidazole fiber has a root mean square roughness of 30 nm or less. If the mean square roughness of the fiber surface is 30 nm or less, the smoothness of the fiber surface becomes high, and the gaps between the fibers can be further reduced when the fibers are aligned in a uniaxial direction. The root mean square roughness of the pyridobisimidazole fiber is more preferably 22 nm or less, and even more preferably 15 nm or less. In addition, the measuring method of the root mean square roughness of a fiber is mentioned later.

  The pyridobisimidazole fiber is a fiber formed from a pyridobisimidazole polymer. In the pyridobisimidazole polymer, at least 50 mol% of repeating groups are 2,6-diimidazo [4,5-b: 4 ′, 5′-e] -pyridinylene-1,4 (2,5-dihydroxy) phenylene. It is. In the pyridobisimidazole polymer, 75 mol% or more of the repeating groups are 2,6-diimidazo [4,5-b: 4 ′, 5′-e] -pyridinylene-1,4 (2,5-dihydroxy). ) Ladder polymers that are phenylene are preferred. As the pyridobisimidazole polymer, a polymer comprising only 2,6-diimidazo [4,5-b: 4 ′, 5′-e] -pyridinylene-1,4 (2,5-dihydroxy) phenylene is particularly preferable. . Here, 2,6-diimidazo [4,5-b: 4 ′, 5′-e] -pyridinylene-1,4 (2,5-dihydroxy) phenylene is represented by the following chemical formula (1).

  The remaining repeating group in the pyridobisimidazole polymer is the 2,6-diimidazo [4,5-b: 4 ′, 5′-e] -pyridinylene-1,4 (2,5-dihydroxy). In phenylene, the 1,4 (2,5-dihydroxy) phenylene moiety is replaced by a substituted or unsubstituted arylene and / or 2,6-diimidazo [4,5-b: 4 ′, 5′-e ] The pyridinylene moiety is replaced by benzobisimidazole, benzobisthiazole, benzobisoxazole, pyridobisthiazole or pyridobisoxazole.

  Here, 1,4- (2,5-dihydroxy) phenylene of 2,6-diimidazo [4,5-b: 4 ′, 5′-e] -pyridinylene-1,4 (2,5-dihydroxy) phenylene When the moiety is replaced (at most 50 mol%), the replacement group includes arylenedicarboxylic acid (eg, isophthalic acid, terephthalic acid, 2,5-pyridinedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4, A divalent residue excluding two carboxyl groups of 4′-diphenyldicarboxylic acid, 2,6-quinolinedicarboxylic acid or 2,6-bis (4-carboxyphenyl) pyridobisimidazole) is preferred.

  The intrinsic viscosity of the pyridobisimidazole polymer is preferably 10 dl / g or more, more preferably 15 dl / g or more, preferably 30 dl / g or less, more preferably 25 dl / g or less.

  The pyridobisimidazole fiber preferably has a reciprocating wear number of 4000 times or more at break in a wear strength test measured according to JIS L1095 (1999) -9.10.2B, more preferably 4500. Times or more, more preferably 5000 times or more. When the number of reciprocating wear at the time of breaking is 4000 times or more, the generation of fluff is suppressed during the production of the thin layer sheet, and a thin layer sheet with higher quality can be obtained.

  The fiber diameter of the pyridobisimidazole fiber is preferably 8 μm or more, more preferably 9 μm or more, further preferably 10 μm or more, preferably 20 μm or less, more preferably 15 μm or less, and further preferably 12 μm or less. When the fiber diameter of the pyridobisimidazole fiber is within the above range, a thin layer sheet having a thinner thickness and a uniform thickness can be obtained.

  The tensile strength of the pyridobisimidazole fiber is preferably 2.0 GPa or more, more preferably 3.0 GPa or more, still more preferably 3.8 GPa or more, preferably 6.0 GPa or less, more preferably 5.5 GPa or less. More preferably, it is 5.0 GPa or less. When the tensile strength of the pyridobisimidazole fiber is within the above range, processing such as cutting is facilitated, fluff and the like are reduced, and a high-quality thin layer sheet can be obtained.

  The elastic modulus of the pyridobisimidazole fiber is preferably 100 GPa or more, more preferably 130 GPa or more, further preferably 160 GPa or more, preferably 400 GPa or less, more preferably 350 GPa or less, and further preferably 300 GPa or less. When the elastic modulus of the pyridobisimidazole fiber is within the above range, processing such as cutting is facilitated, fluff and the like are reduced, and a high-quality thin layer sheet can be obtained. In addition, the elasticity modulus of the said pyridobisimidazole fiber shall refer to the apparent Young's modulus prescribed | regulated to JISL1013.

3. Manufacturing method of pyridobisimidazole fiber An example of the manufacturing method of the said pyridobisimidazole fiber bundle is demonstrated. The method for producing a pyridobisimidazole fiber bundle includes, for example, a spinning dope preparation step, a spinning step, a coagulation / washing step, a neutralization step, and a drying step.

  In the spinning dope preparation step, the spinning dope is prepared by dissolving the pyridobisimidazole polymer in a solvent. Examples of the solvent include non-oxidizing acids that can dissolve the pyridobisimidazole polymer. Examples of the solvent include polyphosphoric acid, methanesulfonic acid, high-concentration sulfuric acid, or a mixed solution thereof. Among these, as a solvent, polyphosphoric acid and methanesulfonic acid are preferable, More preferably, it is polyphosphoric acid.

  The polymer concentration in the spinning dope is preferably 7% by mass or more, more preferably 10% by mass or more, and further preferably 14% by mass or more. The maximum polymer concentration in the spinning dope is limited by practical handling properties such as polymer solubility and dope viscosity. Due to their limiting factors, the polymer concentration usually does not exceed 20% by weight.

  The pyridobisimidazole polymer and the spinning dope used in the present invention are synthesized by a known method (see JP-T-8-509516, etc.). For example, a suitable pyridobisimidazole monomer can be used in a stepwise or constant increase from about 60 ° C. to 230 ° C. in a non-oxidizing and dehydrating acid solution under non-oxidizing atmosphere and high speed stirring and high shear conditions. It can be synthesized by raising the temperature at a temperature rate.

  In the spinning step, the spinning dope is supplied to a spinning section of the apparatus and is spun from a spinneret. A known apparatus can be used for the spinning process. The temperature of the spinning dope when spinning from the spinneret is usually 100 ° C. or higher and 250 ° C. or lower. The plurality of fine holes of the spinneret are usually arranged in a circumferential shape or a lattice shape, but other arrangements may be used. The number of pores formed in the spinneret is not particularly limited, and may be adjusted as appropriate so that the spun yarns are not fused.

  The spun yarn is relatively high in a sufficiently long draw zone, as described in US Pat. No. 5,296,185, to obtain a sufficient spin-draw ratio (SDR). It is desirable to cool uniformly with a rectified cooling air at a temperature (above the spinning dope solidification temperature and below the spinning temperature). The length of the draw zone is preferably a length that completes solidification in a non-solidifying gas such as nitrogen, argon, or air, and is usually determined by a single-hole discharge amount. In order to obtain good fiber properties, it is preferable that the take-out stress of the draw zone is 2 g / dtex or more in terms of polymer (assuming that only the polymer is stressed). In the present invention, “solidification” means that the spinning dope is cooled to simply change from a molten state to a solid state, and the dope solvent has not been completely removed from the polymer at this stage.

  In the coagulation / washing step, the polymer is coagulated by immersing the spun yarn in a coagulation liquid and eluting the acid solvent. In the present invention, “coagulation” means precipitation of pyridobisimidazole dissolved in an acid solvent. As described above, the spun yarn drawn in the draw zone is guided to the coagulation bath and immersed in the coagulation liquid. Examples of the coagulating liquid include water; alcohols such as methanol and ethanol; ketones such as acetone; glycols such as ethylene glycol; and the like. Among these, water is preferable in terms of safety and simplicity.

  Here, in order to produce the pyridobisimidazole fiber excellent in surface smoothness of the present invention, it is important to slow down the solidification rate of the pyridobisimidazole polymer in order to change the fiber surface structure precisely. . That is, by slowing the solidification rate of the polymer, the structure can be changed in the inner and outer layers of the fiber, and a high crystal orientation on the fiber surface is realized. Thus, if the crystal orientation on the fiber surface increases, the structure of the fiber surface becomes dense and the surface smoothness is improved.

  Examples of a method for slowing the coagulation rate of the polymer include a method in which an acid (for example, polyphosphoric acid) similar to the acid solvent contained in the spun yarn is included in the coagulation liquid; And a method using a non-aqueous coagulating liquid as the liquid. Two or more of these methods can be combined.

  When an acid solvent is contained in the coagulation liquid, the acid concentration in the coagulation liquid is preferably 50% by mass or more, more preferably 55% by mass or more, still more preferably 60% by mass or more, and preferably 80% by mass or less. More preferably, it is 70 mass% or less, More preferably, it is 65 mass% or less. If the concentration of the dope solvent in the coagulation liquid is 50% by mass or more, the solidification of the polymer is delayed, and the surface roughness of the resulting fiber becomes smaller, and if it is 80% by mass or less, the decrease in fiber strength is suppressed. .

  When lowering the coagulation liquid temperature, the temperature is preferably 5 ° C. or lower, more preferably 4 ° C. or lower, still more preferably 0 ° C. or lower, preferably −30 ° C. or higher, more preferably −15 ° C. or higher. If the coagulation liquid temperature is 5 ° C. or lower, the solidification of the polymer will be delayed, and the surface roughness of the resulting fiber will be lower, and if it is −30 ° C. or higher, condensation occurring around the coagulation bath can be reduced. It is preferable in the operation of the manufacturing machine.

  When a non-aqueous coagulating liquid is used as the coagulating liquid, the non-aqueous coagulating liquid includes organic substances having an affinity for water, such as alcohols such as methanol and ethanol; ketones such as acetone; glycols such as ethylene glycol; A solvent is preferred. In addition, a non-aqueous coagulant may be used independently and may use 2 or more types together. Moreover, you may use water together as a coagulating liquid.

  In the neutralization step, the acid solvent remaining in the pyridobisimidazole fiber obtained in the coagulation / washing step is neutralized. The neutralization solution used in the neutralization step is not particularly limited, and examples thereof include a sodium hydroxide aqueous solution, ammonia water, and a sodium carbonate aqueous solution. In addition, it is desirable to wash the pyridobisimidazole fiber again after neutralization.

  In the drying step, the coagulating liquid or the like in the pyridobisimidazole fiber (which means that the neutralized dope solvent is included) is volatilized. The drying temperature is not particularly limited as long as the coagulating liquid is volatilized, but is preferably 150 ° C or higher, more preferably 200 ° C or higher, still more preferably 220 ° C or higher, and preferably 400 ° C or lower, more preferably. It is 300 degrees C or less, More preferably, it is 270 degrees C or less. The moisture content of the dried pyridobisimidazole fiber is preferably 3% by mass or less, more preferably 2% by mass or less, and still more preferably 1% by mass or less. In addition, what is necessary is just to measure the moisture content of a pyridobis imidazole fiber according to JISL1013.

  Moreover, the pyridobisimidazole fiber after drying may be heat-treated under tension as necessary for the purpose of improving the elastic modulus. In this case, the heat treatment temperature is preferably 400 ° C. or higher, more preferably 500 ° C. or higher, further preferably 550 ° C. or higher, 700 ° C. or lower, more preferably 680 ° C. or lower, more preferably 630 ° C. or lower. . Further, the tension during the heat treatment is preferably 0.3 g / dtex or more, more preferably 0.5 g / dtex or more, further preferably 0.6 g / dtex or more, and preferably 1.2 g / dtex or less, more preferably 1.1 g / dtex or less, more preferably 1.0 g / dtex or less.

4). Resin Next, the resin will be described. As the resin, any of a thermoplastic resin and an uncured (including semi-cured) thermosetting resin composition can be used. Examples of the thermoplastic resin include polyester resin, nylon resin, polyamide resin, polyimide resin, polyamide / imide resin, rigid polyimide resin, and polyethylene resin.

  Examples of the thermosetting resin composition include a curable epoxy resin composition. Typical examples of the epoxy resin used in the curable epoxy resin composition include glycidyl ether type epoxy resins obtained by reaction of phenols or alcohols with epichlorohydrin; glycidyl esters obtained by reaction of carboxylic acids with epichlorohydrin. Type epoxy resin; glycidyl type epoxy resin obtained by reaction of amines or cyanuric acid with epichlorohydrin; internal epoxy resin obtained by oxidation of double bond; epoxy resin modified BT resin; epoxy resin modified cyanate ester resin.

  Examples of the curing agent for the curable epoxy resin include conventional epoxy resin curing agents such as polyamine curing agents, polymercaptan curing agents, anionic polymerization catalyst curing agents, cationic polymerization catalyst curing agents, and latent curing agents. Etc. can be used. In addition, the curable epoxy resin composition may be used by blending an amount of fillers and additives in a range that does not impair the original properties in order to impart desired performance depending on the application.

  The content of the resin (thermoplastic resin or uncured (including semi-cured) curable resin composition) in the thin layer sheet is preferably 30% by mass or more, more preferably 40% by mass or more, and further preferably 45% by mass. % Or more, preferably 75% by mass or less, more preferably 65% by mass or less, and still more preferably 60% by mass or less.

5). Production method of thin layer sheet Hereinafter, as an example of a method for producing a thin layer sheet using the pyridobisimidazole fiber bundle, the fiber layer in which the (I) pyridobisimidazole fiber bundle is oriented in a certain direction is used. Next, a method for producing a thin-layer sheet according to an embodiment formed by impregnating a resin; or (II) an embodiment formed by impregnating a woven fabric composed of pyridobisimidazole fiber bundles with a resin will be described.

  When producing a thin layer sheet, first, a pyridobisimidazole fiber bundle is opened or flattened. Thus, by opening or flattening the fiber bundle, the thickness of the obtained thin layer sheet can be further reduced. The method for opening the fiber bundle is not particularly limited. For example, an electric fiber opening method may be employed. The method for flattening the fiber bundle is not particularly limited, and examples thereof include a method using air, a method using water flow, a method using static electricity, and a method of pressing against a bar.

  The opened or flattened pyridobisimidazole fiber bundle is wound on a reel. At this time, in the flattened fiber bundle, when the fiber bundle is wound around a reel without applying tension, the folded state may be slightly restored. In order to prevent this, an oil agent or an adhesive may be applied to the pyridobisimidazole fiber bundle and wound up.

  Next, the fiber bundles that have been opened or flattened are arranged to form a fiber layer. The method for arranging the fiber bundles is not particularly limited, and examples thereof include arranging the fiber bundles in parallel in a uniaxial direction; or forming the fiber bundles in plain weave. In the case where the fiber bundles are aligned in parallel in the uniaxial direction, for example, after weaving the fiber bundles using a loom, the portion where the weft runs may be cut off.

  The fiber layer formed as described above is impregnated with resin. A method for impregnating the resin into the fiber layer is not particularly limited, and examples thereof include a method of spraying a varnish containing a resin onto the fiber layer; a method of applying a pressure after a resin sheet is attached to the fiber layer; In order to uniformly impregnate the fiber layer with the resin, it is preferable to hold for a certain time while applying temperature and pressure.

  Moreover, when impregnating resin with a fiber layer, it is preferable to dilute resin with a solvent. As the solvent, methyl ethyl ketone, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, or the like is used. When the solvent is used, it is necessary to volatilize the solvent after the resin impregnation, but the drying method at this time is not particularly limited, and a known method may be adopted.

  The thin-layer sheet of the present invention contains pyridobisimidazole fibers as a reinforcing material, and has high quality with reduced gaps between pyridobisimidazole fibers. Therefore, the thin layer sheet of the present invention is a resin substrate constituting a printed wiring board; It can be applied to sports-related materials such as rockets, rocket insulation, rocket casing, pressure vessels, space suits, etc .; speaker cones, etc.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented within a range that can meet the purpose described above and below. All of which are within the scope of the present invention. The following methods were used for various measurements.

1. Intrinsic viscosity The pyridobisimidazole polymer was adjusted to a concentration of 0.5 g / l using methanesulfonic acid as the solvent. The viscosity of the obtained polymer solution was measured in a thermostatic bath at 25 ° C. using an Ostwald viscometer to determine the intrinsic viscosity.

2. Surface Roughness Pyridobisimidazole fibers were washed with a mixed solution of ethanol and n-hexane, dried, and then subjected to a test.
The mean square roughness of the fiber surface was evaluated using an atomic force microscope (Seiko Instruments (SII), “SPI3800N-SPA300”). A Si rectangular cantilever (“SI-DF3”, spring constant 2 N / m, length 450 μm, width 60 μm, thickness 4 μm) was used for the probe. A 100 μm scanner was used as the scanner, and the DFM mode was adopted as the observation mode.
Scanning was performed at a speed of 0.5 Hz, the scanning direction was parallel to the fiber axis, and the atmosphere was measured at a temperature of 20 ° C. and a relative humidity of 65%. The observation visual field range was a square area of 5 μm square, and after observation, planarization processing was performed by performing three-dimensional tilt correction of software attached to the atomic force microscope. However, in order to take into account the distortion that occurs when the image is flattened due to the presence of the curvature of the fiber, the mean square roughness of only the 3 μm square area at the center of the visual field was calculated.
In addition, the measurement was performed at 10 points or more at random for each fiber. The mean square roughness at each measurement location was determined, the average value was calculated, and the measured value of the fiber was taken. Here, in the present invention, the root mean square roughness is root mean square roughness (Rms (Root mean square)) expressed by the following formula (1).

In the formula, Z _i represents the height at each measurement location, Z ₀ represents the average height over the entire measurement location, and N represents the number of measurement locations.

3. Tensile strength / elastic modulus of fiber Pyridobisimidazole fiber is placed in a standard test room (temperature: 20 ± 2 ° C., relative humidity (RH): 65 ± 2%) with ultraviolet light and visible light blocked. After standing for 24 hours or more, the tensile strength and elastic modulus (apparent Young's modulus) of the fiber were measured according to JIS L 1013 (1999). A constant-speed extension type was used as a test machine, and measurement was performed under the conditions of a sample length of 200 mm and a tensile speed of 200 mm / min.

4). Abrasion strength The abrasion strength of the pyridobisimidazole fiber was measured in accordance with JIS L 1095 (1999) -9.10.2B.

5). Thin Layer Sheet Thickness The thickness of the thin layer sheet was measured using an upright dial gauge (manufactured by Ozaki Seisakusho, PEACOCK (registered trademark) R series).

6). Sheet quality The sheets obtained by the production examples were evaluated by visual inspection. Specifically, the sheet was observed through light, and how much pyridobisimidazole fiber was spread in the sheet was evaluated according to the following criteria.
○: Light does not leak when observed through light.
X: Light leaks when observed through light.

Production of pyridobisimidazole fiber Production Example 1
A spinning dope having a polymer concentration of 14% by mass was prepared by dissolving pyridobisimidazole-2,6-diyl (2,5-dihydroxy-p-phenylene) having an intrinsic viscosity [η] of 22 dl / g in polyphosphoric acid. .
Using this spinning dope, spinning was performed under conditions such that the single yarn filament diameter was 11.5 μm and the fineness was 1.65 dtex. That is, the obtained spinning dope was spun from a spinneret having a pore diameter of 0.20 mm and a number of holes of 166 at a spinning temperature of 175 ° C. Allowed to cool. The spun yarn that passed through the quench chamber was immersed in a coagulation bath while converging on the multifilament to coagulate the filament. As the coagulation liquid, an aqueous phosphoric acid solution having a concentration of 60% by mass was used, and the coagulation liquid temperature was set to −5 ° C.
The coagulated spun yarn was washed with water until the residual phosphorus concentration in the filament was 5000 ppm or less, neutralized with 1% NaOH aqueous solution for 5 seconds, and further washed with water for 10 seconds. After washing with water, it is dried until the moisture content becomes 2% by mass, and pyridobisimidazole fiber No. 1 is obtained. 1 was obtained. The evaluation results for the obtained pyridobisimidazole fiber are shown in Table 1.

Production Example 2
In the coagulation step, pyridobisimidazole fiber No. 1 was prepared in the same manner as in Production Example 1 except that the coagulation liquid temperature was changed to 4 ° C. 2 was obtained. The evaluation results for the obtained pyridobisimidazole fiber are shown in Table 1.

Production Example 3
In the coagulation step, pyridobisimidazole fiber No. 1 was prepared in the same manner as in Production Example 1 except that the coagulation liquid was changed to a phosphoric acid aqueous solution having a concentration of 20% by mass and the coagulation liquid temperature was changed to 20 ° C. 3 was obtained. The evaluation results for the obtained pyridobisimidazole fiber are shown in Table 1.

Production of thin-layer sheet The pyridobisimidazole fibers obtained in Production Examples 1 to 3 were opened. Opening was performed using an electric opening device. That is, the pyridobisimidazole fiber was introduced into the electrode through a guide, and a voltage of −300 V was applied to open the fiber, and then wound on a reel.
Next, the opened yarn was unwound from the reel, and the opened yarn was arranged in parallel so that the entire width was 30 cm. On the other hand, 100 parts by mass of bisphenol A type epoxy resin (manufactured by Japan Epoxy Resin, jER (registered trademark) 828EL) and 3 parts by mass of 2-methyl-4-methylimidazole were dissolved in 100 parts by mass of methyl ethyl ketone to prepare a varnish. The obtained varnish was impregnated into spread yarns arranged in parallel as described above to prepare a prepreg. The resin (bisphenol A type epoxy resin and 2-methyl-4-methylimidazole) content in the obtained prepreg was 50% by mass. The obtained prepreg was press-molded using a press machine at a temperature of 80 ° C. and a pressure of 2.0 MPa (20 kgf / cm ² ) for 1 hour, and the resin was cured to the B stage to obtain a thin layer sheet. The obtained thin layer sheet was evaluated, and the results are shown in Table 1.

  Pyridobisimidazole fiber no. 1 and 2 have a mean square roughness of the fiber surface of 30 nm or less. When a thin layer sheet was used using these fibers, a high quality thin layer sheet in which the gap between the fibers was further reduced was obtained because of high fiber ordering. On the other hand, pyridobisimidazole fiber No. 1 having a mean square roughness of the fiber surface exceeding 30 nm. When No. 3 was used, the order of the fibers was low and the gaps between the fibers increased, so the quality of the resulting thin layer sheet was low.

  The thin layer sheet of the present invention is thin and easy to mold into an arbitrary shape. Therefore, the thin layer sheet containing the pyridobisimidazole fiber of the present invention can be used for various applications that require heat resistance and flame retardancy.

Claims (5)

  A thin layer sheet comprising pyridobisimidazole fiber having a mean square roughness of fiber surface of 30 nm or less and a resin.   2. The thin layer according to claim 1, wherein the pyridobisimidazole fiber has 4000 times or more of reciprocating wear at break in a wear strength test measured according to JIS L1095 (1999) -9.10.2B. Sheet.   The thin layer sheet according to claim 1 or 2, wherein the thickness is 5 µm or more and 100 µm or less. The pyridobisimidazole fiber is
A spinning process of spinning a spinning dope containing a pyridobisimidazole polymer and polyphosphoric acid from a spinneret; and
2. A coagulation step in which the spun yarn is immersed in an aqueous phosphoric acid solution having a concentration of 50% by mass or more and 80% by mass or less to coagulate a pyridobisimidazole polymer. The thin layer sheet as described in any one of -3.   The thin-layer sheet according to claim 4, wherein the pyridobisimidazole fiber is produced by setting the temperature of the aqueous phosphoric acid solution in the coagulation step to -30 ° C or higher and 5 ° C or lower.