JP5254593B2 - Thermal insulation / sound absorbing material and aircraft including fiber assembly including non-thermoplastic polyimide fiber - Google Patents

Description

  The present invention relates to a heat insulating and sound absorbing material using a fiber assembly containing non-thermoplastic polyimide fibers.

For thermal insulation and sound absorption applications used on the outer walls of current aircraft, low bulk density glass wool fibers packed in bags (Insulaton Blanket) are widely used. As a characteristic of glass wool, it is nonflammable, has excellent heat insulation performance, and is a material excellent in sound absorption characteristics, so it is widely used for current aircraft applications (for example, Non-Patent Documents 1 and 2, Patent Documents). 1-2).
On the other hand, the material for using as a substitute product of the said glass wool combining non-thermoplastic fiber and thermoplastic fiber is developed (for example, refer patent documents 3-4).
Aviation Technology, No.581, 34-39 (2003) “The 40th Aircraft Symposium of the Japan Aerospace Society” 267-270 (2002) US Pat. No. 6,551,951 US Pat. No. 6,627,561 US Pat. No. 6,383,623 US Pat. No. 6,579,396

As described in Non-Patent Documents 1 and 2 above, it is at least necessary that the heat insulating and sound absorbing material for aircraft use be a material that meets the flame retardant standards. Therefore, it is required to be a lightweight member. However, in the conventional glass wool, although it is a material that can meet the flame retardancy standard, the glass density (2.5 g / cm ³ ) is heavier and lighter than high heat-resistant fibers excluding fluorine fibers. there was a difficult problem at present (for example, in the m- aramid fibers, 1.38g / ^cm 3, the p- aramid fiber, 1.44g / cm ^3, a polyimide fiber, 1.41g / ^cm 3). Therefore, there is a need for a heat insulating / absorbing material for aircraft applications that overcomes the conventional flame retardant standards, is lightweight, and has excellent sound absorbing characteristics. Therefore, in Patent Documents 3 to 4, there is a report of a non-thermoplastic fiber that is produced by joining with a thermoplastic resin. However, in this production method, there is a problem that the heat resistance is lowered because the thermoplastic resin is used. there were.

As a result of intensive studies to solve the above problems, the present inventors have obtained a fiber assembly containing at least a non-thermoplastic polyimide fiber having a curved portion and having a bulk density of 1.0 to 10.0 kg / m ^3. It is considered that there is a possibility of obtaining a heat insulating / sound absorbing material excellent in heat insulating performance, sound absorbing performance, and weight reduction by using the heat insulating / sound absorbing material used, and the present invention has been achieved based on these findings. The structure of the heat insulating and sound absorbing material of the present invention will be described in detail below.

That is, the heat insulating / sound absorbing material of the present invention is a heat insulating / sound absorbing material using a fiber assembly having at least a non-thermoplastic polyimide fiber having a curved portion and having a bulk density of 1.0 to 10.0 kg / m ^3. .

  The non-thermoplastic polyimide fiber preferably contains at least pyromellitic dianhydride and 4,4-diaminodiphenyl ether as raw materials.

  Another invention of the present invention is a heat insulating / sound absorbing material using the fiber assembly and a packaging material for the fiber assembly.

  The fiber aggregate packaging material is preferably made of at least one resin selected from the group consisting of polyimide resin, fluorine resin, polyethylene terephthalate resin, polyether ketone resin, and polyether ketone ketone resin.

  Further, another invention of the present invention is a heat insulating / sound absorbing material for aircraft use using the heat insulating / sound absorbing material.

  Another invention of the present invention is an aircraft using the heat insulating and sound absorbing material.

  The heat insulating and sound absorbing material of the present invention is lightweight and excellent in sound absorbing characteristics, and is therefore a heat insulating and sound absorbing material that is most suitable for aircraft use, and is a material useful for reducing the weight of an aircraft and improving fuel consumption.

The heat insulating / sound absorbing material comprising the non-thermoplastic polyimide fiber of the present invention includes a non-thermoplastic polyimide fiber having at least a curved portion, and heat insulation using a fiber aggregate having a bulk density of 1.0 to 10.0 kg / m ^3.・ Sound absorbing material.

  A method for producing such a heat insulating and sound absorbing material will be described in detail below.

  Non-thermoplastic in the present invention refers to a storage elastic modulus at 250 ° C. or higher when a 25 μm-thick polyimide film is prepared from a polyamic acid solution used as a raw material for polyimide fibers and the dynamic viscoelastic behavior of the film is measured. It has an inflection temperature of E ′. If it explains in full detail, the manufacturing method of a polyimide film is as follows. In other words, a polyamic acid solution is applied on a glass substrate so that the final polyimide film has a thickness of 25 μm, and is put into an oven cooled to room temperature. Raise the temperature at. And a polyimide film can be produced on a glass substrate by cooling slowly until it becomes room temperature. The measurement of the dynamic viscoelastic behavior is to peel off the polyimide film, cut the polyimide film into a 40 mm length with a width of 9 mm, and set it in the DMS200 device manufactured by Seiko Electronics Co., Ltd. Can be performed under the following measurement conditions.

<Measurement conditions>
Profile temperature: 20 ° C to 400 ° C (temperature increase rate: 3 ° C / min)
Frequency: 5Hz
Lamp. (AC distortion amplitude target value): 20 μm
Fbase (minimum value of tension during measurement): 0 g
F0gain (coefficient when the tension is changed according to the AC force amplitude during measurement): 3.0.

  By the measurement under these measurement conditions, the values of the storage elastic modulus E ′ and the loss elastic modulus E ″ at the profile temperature described above are obtained. The inflection point of the storage elastic modulus means that the storage elastic modulus rapidly decreases. 1, the tangent 50 to the straight line until the storage elastic modulus starts to change and the storage elastic modulus starts to change and changes. The tangent line 51 with respect to the finished straight line is drawn to obtain the temperature of the intersection 52. This temperature becomes the inflection point of the storage elastic modulus.The non-thermoplastic polyimide fiber in the present invention has a temperature of this inflection point of 250. It consists of a polyimide fiber having a temperature of at least ° C.

  The non-thermoplastic polyimide fiber in the present invention is preferably a polyimide fiber characterized by containing at least pyromellitic dianhydride and 4,4-diaminodiphenyl ether as raw materials. By containing at least pyromellitic dianhydride and 4,4-diaminodiphenyl ether, the heat resistance of the polyimide fiber is improved.

  In this invention, in addition to the said pyromellitic dianhydride, it is also possible to use the following acid dianhydride together.

  For example, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane dianhydride, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexafluoropropane dianhydride 2,2-bis (4-hydroxyphenyl) propanedibenzoate-3,3 ′, 4,4′-tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride 2,3,3 ′, 4-biphenyltetracarboxylic dianhydride, 2,2′-hexafluoropropylidenediphthalic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid Anhydride, 4,4'-oxydiphthalic dianhydride, 3,3 ', 4,4'-diphenylsulfone tetracarboxylic dianhydride, pyromellitic dianhydride, 1,2,5,6-naphthalenetetra Carbo Acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, methylcyclobutanetetracarboxylic dianhydride, 1,2,3,4-tetracarboxybutane An anhydride may be used in combination.

  Among them, among the acid dianhydrides that can be used in combination to improve the heat resistance and chemical resistance of the polyimide fiber, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4, It is preferable to use 4′-benzophenonetetracarboxylic dianhydride in combination.

  In addition, the amount of acid dianhydride components other than pyromellitic dianhydride used as acid dianhydride is less than 70 mol when the total acid dianhydride is 100 mol. It is preferable because it is not present. A particularly preferred amount used is preferably 50 mol or less.

  In the present invention, in addition to 4,4-diaminodiphenyl ether, the following diamine may be used in combination.

  For example, 3,3′-diaminodiphenyl ether, 3,4-diaminodiphenyl ether, m-phenylenediamine, p-phenylenediamine, 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, 4,4′- Diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfide, bis [4- (4-aminophenoxy) phenyl] sulfone, (4-aminophenoxyphenyl) (3-aminophenoxyphenyl) phenyl] sulfone, bis [4- ( 3-aminophenoxy) phenyl] sulfone, 3,3′-diaminobenzanilide, 3,4′-diaminobenzanilide, 4,4′-diaminobenzanilide, bis [4- (3-aminophenoxy) phenyl] methane, Bis [4- (4-aminophenoxy) phenol Enyl] methane, [4- (4-aminophenoxyphenyl)] [4- (3-aminophenoxyphenyl)] methane, 1,1-bis [4- (3-aminophenoxy) phenyl] ethane, 1,1- Bis [4- (4-aminophenoxy) phenyl] ethane, 1,1- [4- (4-aminophenoxyphenyl)] [4- (3-aminophenoxyphenyl)] ethane, 1,2-bis [4- (3-Aminophenoxy) phenyl] ethane, 1,2-bis [4- (4-aminophenoxy) phenyl] ethane, 1,2- [4- (4-aminophenoxyphenyl)] [4- (3-amino Phenoxyphenyl)] ethane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2- [4- (4-aminophenoxyphenyl)] [4- (3-aminophenoxyphenyl)] The Lopan, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexa Fluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2- [4- (4-aminophenoxyphenyl) ] [4- (3-aminophenoxyphenyl)]-1,1,1,3,3,3-hexafluoropropane, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (3- Aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′- Bis (3-Ami Phenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, polytetramethylene oxide-di-P-aminobenzoate, poly (tetramethylene / 3-methyltetramethylene ether) glycol bis (4-aminobenzoate), trimethylene-bis (4-amino) Benzoate), p-phenylene-bis (4-aminobenzoate), m-phenylene-bis (4-aminobenzoate), bisphenol A-bis (4-aminobenzoate) can be used in combination.

  In particular, in order to improve the heat resistance and chemical resistance of the finally obtained polyimide resin, aromatic diamines such as 3,4-diaminodiphenyl ether, m-phenylenediamine, p-phenylenediamine, bis [ 4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] methane, 4,4′-diaminodiphenylsulfone, 3 , 3′-diaminodiphenylsulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, and 1,3-bis (3-aminophenoxy) benzene are preferably used in combination. In particular, it is preferable to use p-phenylenediamine in combination.

  Furthermore, as a diamino compound having a carboxyl group or a hydroxyl group in the side chain, for example, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid, 3,3′-diamino-4 , 4′-dicarboxybiphenyl, 4,4′-diamino-3,3′-dicarboxybiphenyl, 4,4′-diamino-2,2′-dicarboxybiphenyl, [bis (4-amino-2-carboxy ) Phenyl] methane, [bis (4-amino-3-carboxy) phenyl] methane, [bis (3-amino-4-carboxy) phenyl] methane, [bis (3-amino-5-carboxy) phenyl] methane, 2,2-bis [3-amino-4-carboxyphenyl] propane, 2,2-bis [4-amino-3-carboxyphenyl] propane, 2,2-bis [3-amino-4-carboxyphenyl] hexafluoro Ropropane, 2,2-bis [4-amino-3-carboxyphenyl] hexafluoropropane, 3,3′-diamino-4,4′-dicarboxydiphenyl ether, 4,4′-diamino-3,3′-di Carboxydiphenyl ether, 4,4′-diamino-2,2′-dicarboxydiphenyl ether, 3,3′-diamino-4,4′-dicarboxydiphenyl sulfone, 4,4′-diamino-3,3′-dicarboxy Diphenylsulfone, 4,4′-diamino-2,2′-dicarboxydiphenylsulfone, 2,3-diaminophenol, 2,4-diaminophenol, 2,5-diaminophenol, 3,5-diaminophenol, 3, 3'-diamino-4,4'-dihydroxybiphenyl, 4,4'-diamino-3,3'-dihydro Cibiphenyl, 4,4′-diamino-2,2′-dihydroxybiphenyl, 4,4′-diamino-2,2 ′, 5,5′-tetrahydroxybiphenyl, 3,3′-diamino-4,4 ′ -Dihydroxydiphenylmethane, 4,4'-diamino-3,3'-dihydroxydiphenylmethane, 4,4'-diamino-2,2'-dihydroxydiphenylmethane, 2,2-bis [3-amino-4-hydroxyphenyl] propane 2,2-bis [4-amino-3-hydroxyphenyl] propane, 2,2-bis [3-amino-4-hydroxyphenyl] hexafluoropropane, 2,2-bis [3-amino-4-hydroxy Phenyl] hexafluoropropane, 3,3′-diamino-4,4′-dihydroxydiphenyl ether, 4,4′-diamino-3,3′- Hydroxydiphenyl ether, 4,4′-diamino-2,2′-dihydroxydiphenyl ether, 3,3′-diamino-4,4′-dihydroxydiphenyl sulfone, 4,4′-diamino-3,3′-dihydroxydiphenyl sulfone, 4,4′-diamino-2,2′-dihydroxydiphenylsulfone, 3,3′-diamino-4,4′-dihydroxydiphenyl sulfide, 4,4′-diamino-3,3′-dihydroxydiphenyl sulfide, 4, 4'-diamino-2,2'-dihydroxydiphenyl sulfide, 3,3'-diamino-4,4'-dihydroxydiphenyl sulfoxide, 4,4'-diamino-3,3'-dihydroxydiphenyl sulfoxide, 4,4 ' -Diamino-2,2'-dihydroxydiphenylsulfur Xoxide, 2,2-bis [4- (4-amino-3-hydroxyphenoxy) phenyl] propane, 4,4′-bis (4-amino-3-hydroxyphenoxy) biphenyl, 2,2-bis [4 -(4-amino-3-hydroxyphenoxy) phenyl] sulfone, 4,4'-diamino-3,3'-dihydroxydiphenylmethane, 4,4'-diamino-2,2'-dihydroxydiphenylmethane, 2,2 -Bis [3-amino-4-carboxyphenyl] propane and 4,4'-bis (4-amino-3-hydroxyphenoxy) biphenyl can be partially used together.

  It is preferable to use a carboxyl group or a diamino compound having a hydroxyl group in such a side chain, since the polyimide fiber is easily cured when cured with another reactive resin (for example, an epoxy compound or an isocyanate compound). Further, it is preferable to provide reaction active sites such as an epoxy resin, since the fibers can be bonded by a resin that undergoes a crosslinking reaction such as an epoxy compound or an isocyanate compound, so that the entanglement between the fibers increases and the heat resistance is improved.

  As a reaction method of reactive compounds such as epoxy compounds and isocyanate compounds, a method of obtaining crosslinked polyimide fibers by immersing the finished polyimide fibers in a reactive resin solution and then drying by heating, or reactive resin during spinning A polyimide fiber can be obtained by employing a method such as spinning while spraying the solution.

  In the present invention, the amount of the diamine that can be used in combination with 4,4-diaminodiphenyl ether is preferably 80 mol or less when the total diamine is 100 mol, because the heat resistance is not impaired. A particularly preferred amount used is preferably 70 mol or less. In addition, it is preferable to appropriately select the ratio of the aromatic diamine and the diamino compound having a carboxyl group or a hydroxyl group in the side chain. In particular, a diamino compound having a carboxyl group or a hydroxyl group in the side chain is preferable because the storage stability of the polyamic acid solution can be improved by using it at 20 mol or less when the total diamine is 100 mol. Moreover, a particularly preferable use amount is 15 mol or less.

  Examples of the organic solvent used in the polyamic acid solution of the present invention include organic polar amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and γ-butyrolactone, tetrahydrofuran Water-soluble ether compounds such as dioxane and dioxolane, water-soluble alcohol compounds such as propylene glycol and ethylene glycol, water-soluble ketone compounds such as acetone and methyl ethyl ketone, and water-soluble nitrile compounds such as acetonitrile and propionitrile are used. . These solvents can be used as a mixed solvent of two or more kinds, and are not particularly limited. Among these, N, N-dimethylformamide, N, N-dimethylacetamide, and N-methyl-2-pyrrolidone are preferable because the resin concentration of the polyamic acid solution can be increased.

  The polyamic acid solution suitably used in the present invention is a polyamic acid solution obtained by reacting the above acid dianhydride and diamine in the above organic solvent.

  In particular, in the production of polyamic acid, it is preferable to use a high-purity acid dianhydride in order to obtain a polyamic acid solution that can be easily spun by increasing the molecular weight. The purity of the acid dianhydride preferred in the present invention is preferably that the acid dianhydride having a ring-closed structure is contained at a high purity of 98% or more, particularly preferably a high purity of 99% or more. is there.

  In the method for producing a polyamic acid solution according to the present invention, the amount of the acid dianhydride and the diamine used is preferably adjusted to 0.90 to 1.10. A polyamic acid solution can be prepared. More preferably, the reaction is carried out at 0.95 to 1.05 to form a polyamic acid. It is preferable to react at such a reaction ratio because a polyimide fiber excellent in heat resistance and chemical resistance can be produced without causing a decrease in molecular weight upon imidation from polyamic acid to polyimide.

  The polymer concentration of the polyamic acid solution is 0.1 to 50% by weight, particularly preferably 1 to 40% by weight, as the solid content concentration. As the polymerization conditions for the polyamic acid, the target polyamic acid can be polymerized by stirring at −20 to 60 ° C., preferably 50 ° C. or less in an inert gas atmosphere.

  The polyamic acid solution is mixed with one or more dehydrating agents, imidization catalysts, various fillers, antioxidants, flame retardants, antifoaming agents, lubricants, colorants, and the like before spinning. You can also. As the dehydrating agent, acetic anhydride is preferably used. As the imidization catalyst, a tertiary amine is preferably used, and more preferably, pyridine, picoline, or isoquinoline is used.

  The polyamic acid solution of the present invention is preferably a solution viscosity of not less than 300 poise and not more than 10,000 poise at 23 ° C., as measured with a B-type viscometer, because it can be stably spun. Particularly preferably, the solution viscosity is controlled to 500 poise or more and 6000 poise or less, and the particularly preferable solution viscosity is preferably controlled to 1000 poise or more and 4000 poise or less.

  Furthermore, the thixo index calculated using the following general formula (1) from the viscosity when measured at 10 revolutions / minute with an E-type viscometer or B-type viscometer and at 2 revolutions / minute is 1. It is preferable that the number is 5 or less because the spun fiber is easily spun stably when stretched by an air stream. In particular, a thixo index greater than 1.5 is not preferable because the solution cannot be spun without stretching when the solution is spun with an air stream. In the spinning method of the present invention, a more preferable thixo index is 1.00 or more and 1.20 or less. Such a range is preferable because the spun fiber can be spun finer.

  Thixo index = (viscosity of polyamic acid at 2 revolutions / minute) / (viscosity of polyamic acid at 10 revolutions / minute) General formula (1).

<Non-thermoplastic polyimide fiber having at least a curved portion>
The non-thermoplastic polyimide fiber having at least a curved portion of the present invention will be described with reference to FIG. 2 which is a micrograph of the produced fiber.
The curved portion in the present invention means, for example, a portion where the fiber is bent halfway like the portion indicated by the white arrow in FIG. More specifically, it means that the fiber is bent like a bow, a circle is drawn, a loop is spiraled, and the like. Moreover, the polyimide fiber which comprises the fiber assembly containing a non-thermoplastic polyimide fiber does not need to have all the curved shape, and may contain the linear polyimide fiber. Furthermore, with the polyimide fiber having a curved portion, the entire polyimide fiber may be curved, or only a part thereof may be curved.

Moreover, it is preferable that the curvature radius of the said curved part exists in the range of 1 micrometer or more and 1 m or less.
By using a fiber having such a curved portion, it becomes bulky while being entangled, and the bulk density becomes small. Such a fiber can be manufactured by adapting the manufacturing method of the polyimide fiber of the present invention.

Moreover, since the fiber assembly containing such a non-thermoplastic polyimide fiber has a high porosity and is excellent in sound absorbing property and heat retaining property, it can be used as a sound absorbing / insulating material. In particular, it can be used as a sound absorbing / insulating material for aircraft applications.
The method for producing a non-thermoplastic polyimide fiber having at least a curved portion according to the present invention will be described below.

<Spinning method>
The method for producing a non-thermoplastic polyimide fiber of the present invention can be produced by using a method for producing a non-thermoplastic polyimide fiber obtained by spinning and laminating the above-mentioned polyamic acid solution with an air stream. Taking up with an air current is a method of drawing and spinning into a fiber while blowing the spinning solution with an air current in the spinning process. In particular, it is a method of spinning by using an air flow as the main external force as an external force.

  A detailed manufacturing apparatus will be described with reference to FIG.

  The non-thermoplastic polyimide fiber manufacturing method of the present invention is a method in which a part of the organic solvent on the surface is obtained by drawing off the polyamic acid solution 5 discharged from the spinneret 2 by the air flow 4 generated by the air flow generator 1 shown in FIG. This is a method of spinning while removing. At this time, the airflow given as an external force is spun while the polyamic acid solution is blown away by the airflow, and also exhibits the effect of drawing the spun fiber by the external force of the airflow. Further, the fiber spun by the air flow increases in specific surface area at a time, so that the solvent contained in the polyamic acid solution volatilizes.

  Further, when the polyamic acid solution is spun, if it is pulled by an air flow, a difference occurs in the dry state between the air flow contact surface of the fiber and the opposite surface (the back surface). When the aggregate of the polyamic acid fibers collected by spinning due to the difference in the dry state is dried, the fibers are bent due to the difference in shrinkage force accompanying the drying. In this way, the bulk density of the polyimide fiber finally obtained can be reduced by bending the fiber.

  The fiber diameter of the non-thermoplastic polyimide fiber of the present invention can be controlled by the orifice diameter of the spinneret 2 and the discharge amount of the polyamic acid solution. The smaller the orifice diameter, the smaller the fiber diameter of the polyimide fiber, and the smaller the discharge amount of the polyamic acid solution, the smaller the fiber diameter of the polyimide fiber.

  As the orifice diameter of the spinneret 2 of the present invention, it is possible to use a product having a diameter of 0.01 mm to 1.00 mm stably when spinning the fiber, and the fiber diameter of the polyimide fiber finally obtained is 100 μm or less, preferably 0.5 to 50 μm, because it becomes easy to control. Particularly preferred orifice diameters are those having a diameter of 0.05 mm to 0.80 mm. The orifice shape of the discharge port of the spinneret 2 can be any shape such as a circle, an ellipse, a star, and an array. In particular, it is preferable to use a circular orifice because the amount of solvent on the surface of the spun fiber can be easily controlled.

  The flow rate of the polyamic acid solution passed through the orifice is appropriately selected from the orifice diameter and solid content concentration. In particular, when the polyimide fiber is thick, the fiber diameter can be controlled to 100 μm or less, preferably 0.5 to 50 μm by decreasing the discharge amount of the polyamic acid solution.

  The airflow 4 for pulling the polyamic acid solution 5 in the present invention preferably has a wind speed of 5 m / sec or more and 400 m / sec or less, and particularly preferably 10 m / min or more and 350 m / sec or less. This is preferable because the fibers can be made thin. Further, the air flow is preferable because the solvent can be efficiently evaporated from the surface of the spun fiber.

The polyamic acid solution drawn by the airflow is collected by the collection device 8. The surface of the collection device 8 is preferably like a wire mesh collection device 11 in order to allow airflow to escape well. In addition, the distance between the collection device 8 and the spinneret 2 is preferably 1 m or more, and particularly preferably 2 m or more so that the fibers of the laminated polyamic acid fiber aggregate 3 do not bind to each other. By controlling the distance between the collecting device 8 and the spinneret 2 to 1 m or more, the solvent concentration on the surface of the spun polyamic acid fiber is lowered, and the overlapping polyamic acid fibers are present independently without being bonded to each other. become. Moreover, since it becomes an aggregate | assembly with a low bulk density of a polyamic acid fiber, the bulk density of the aggregate | assembly consisting of the non-thermoplastic polyimide fiber finally obtained can be controlled to 1.0-10.0 kg / m < ³ >. . In particular, in order to reduce the bulk density, it is preferable to increase the distance between the collection device 8 and the spinneret 2.

  Next, the laminated polyamic acid fiber aggregate 3 is peeled off from the belt and conveyed in the conveying direction 6. The transported polyamic acid fiber aggregate 3 is dried and removed by a heating / drying device 9 in-line or off-line, and is heated and imidized. Moreover, the aggregate 3 of the polyamic acid fibers is transported with its ends fixed, and is heated and dried. Alternatively, it may be placed on a transport table and heated and dried. Moreover, in an offline apparatus, it is also possible to produce a polyimide fiber aggregate by placing the polyamic acid fiber aggregate 3 in a specific molding apparatus and baking it.

  The polyamic acid fiber is preferably heated and dried at a temperature of 80 ° C. or higher and 700 ° C. or lower, and a particularly preferable temperature range is 100 ° C. or higher and 600 ° C. or lower. Heating in such a temperature range is preferable because the residual solvent can be completely removed and the imidization reaction can be efficiently advanced. Further, the heating time is preferably selected as appropriate, and the temperature step of the heating furnace is preferably selected as appropriate.

  The polyamic acid fiber aggregate 3 becomes a polyimide fiber aggregate 7 by firing. The polyimide fiber aggregate 7 is wound by the winding device 10, thereby forming a roll 12 of the polyimide fiber aggregate.

  The fiber diameter of the non-thermoplastic polyimide fiber of the present invention can be appropriately adjusted according to the orifice diameter of the spinneret, the flow velocity / flow rate of the spinning air flow, and the discharge amount of the polyamic acid solution.

  Further, the non-thermoplastic polyimide fibers may be bonded to each other by a binder resin such as a polyimide resin, a polyamide resin, a urea resin, a phenol resin, a urethane resin, a melamine resin, a polyether resin, or a polyether ketone ketone resin.

  A known method can be used as a method for bonding polyimide fibers. For example, the produced polyimide fiber can be bonded by spraying a solution containing a binder resin for bonding, or by impregnating the solution containing the binder resin with heating and drying.

Further, during spinning, the fibers can be bonded in the state of the fiber assembly 3 ′ by passing through an atmosphere sprayed with a solution containing the binder resin. In this case, when the fiber aggregate 3 ′ is heated and dried, the binder resin can be similarly heated and dried, which is efficient and preferable.
Bonding the polyimide fibers in this way is preferable because it tends to have a low bulk specific gravity, which is a feature of the present invention, and the fibers are bonded to each other, so that elasticity and fiber aggregation are improved.

  The non-thermoplastic polyimide fiber of the present invention has a high porosity, and therefore has excellent sound absorption characteristics. In particular, the non-thermoplastic polyimide fiber is suitably used as a heat insulating and sound absorbing material for aircraft use. Moreover, as other uses, it can use suitably for various sound-absorbing materials, such as a sound-absorbing material for building member use, a sound-absorbing material for reducing the noise in a vehicle or a train, and a sound-absorbing material used for an audio equipment, for example.

  In addition, since it has a high porosity, for example, various heat insulation materials such as a heat insulating material for building members, a heat insulating material in a car engine room, a heat insulating material in a car or a train, and a heat insulating material covering various high-temperature pipes. It can be suitably used for the material. Particularly preferably, since it is lightweight, it can be suitably used as a heat insulating material for aircraft applications.

  Moreover, since it is made of non-plastic polyimide fiber, it can be widely used for flame retardant mats such as a flame retardant carpet substitute for aircraft use and a flame retardant blanket substitute which require high flame retardant properties.

  In particular, when the heat insulating and sound absorbing material of the present invention is used for aircraft applications, a structure in which the fiber assembly made of the non-thermoplastic polyimide fiber is wrapped with the packaging material of the fiber assembly from the viewpoint of handling. A heat insulating / sound absorbing material is preferably used.

  The wrapped structure means, for example, a structure in which a bag is formed from a packaging material and the packaging material is put in the packaging material, or the packaging material is attached from both sides so as to sandwich the fiber assembly with an adhesive. This refers to wrapping the fiber assembly in a structure such as a packaging material or a structure covering the surface by applying a resin solution as a raw material of the packaging material to the fiber assembly.

  In particular, the packaging material of the present invention is a packaging material comprising at least one kind of resin of polyimide resin, fluorine resin, polyethylene terephthalate resin, polyether ketone resin, and polyether ketone ketone resin. By using such a resinous packaging material, the weight of the heat insulating and sound absorbing material for aircraft use can be further reduced.

  Of these, polyimide resin, polyether ketone ketone resin, and polyether ketone resin are particularly preferred because they are excellent in weight reduction and fire resistance.

  Further, vapor deposition of a metal such as aluminum on the surface of the resin layer can prevent passage of water vapor or the like through the packaging material.

  The heat insulating and sound absorbing material of the present invention, when used for aircraft applications, is excellent in weight reduction, can improve fuel efficiency, and is excellent in flame retardancy and heat insulating performance. Enough safety to escape. By using such an aircraft, human safety can be ensured, fuel consumption can be improved, and environmental safety can be expressed.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

<Average fiber diameter>
The average fiber diameter was measured by measuring 30 fiber diameters with an electron microscope (JSM-6380LA, manufactured by JEOL Datum Co., Ltd.). For fibers with irregular cross-sections, the maximum fiber width was calculated as the diameter. The average value was defined as the average fiber diameter.

<Determination of non-thermoplasticity of polyimide resin>
The polyamic acid solution was applied onto a glass substrate having a thickness of 1 cm, dried from room temperature to 400 ° C. over 3 hours, and fired. The polyimide film on the completed glass substrate was completely cooled and then submerged by submerging in water. This polyimide film was completely dried in an oven at 50 ° C. for 30 minutes.
The dried polyimide film was cut out to 9 mm width × 40 mm length and set in a DMS200 device manufactured by Seiko Electronics Co., Ltd., and then measured in the tension mode under the following measurement conditions.

<Measurement conditions>
Profile temperature: 20 ° C to 400 ° C (temperature increase rate: 3 ° C / min)
Frequency: 5Hz
Lamp. (AC distortion amplitude target value): 20 μm
Fbase (minimum value of tension during measurement): 0 g
F0gain (coefficient when the tension is changed according to the AC force amplitude during measurement): 3.0.

  By the measurement under these measurement conditions, the values of the storage elastic modulus E ′ and the loss elastic modulus E ″ at the profile temperature described above are obtained. The inflection point of the storage elastic modulus means that the storage elastic modulus rapidly decreases. 1, the tangent 50 to the straight line until the storage elastic modulus starts to change and the storage elastic modulus starts to change and changes. The tangent line 51 with respect to the finished straight line is drawn to find the temperature of the intersection 52. This temperature becomes the inflection point of the storage elastic modulus.

<Measurement of normal incidence sound absorption coefficient>
In accordance with ASTM-E-1050 normal incidence sound absorption coefficient test, sample diameter φ 29 mm, thickness 2.54 cm (1 inch), back air layer 0 mm, measurement frequency range 500-6300 Hz (1/3 octave band) It was measured.

<Method for measuring bulk density>
The obtained non-thermoplastic polyimide fiber aggregate was cut into 10 cm × 10 cm × 2.5 cm, and its weight was measured to measure the bulk density.

<Flammability test method>
The measurement was performed by a method based on FAR 25.856 (a).

(Synthesis Example 1)
The reaction was carried out in a reactor equipped with a stirring blade for stirring the solution in a 2 L glass separable flask subjected to nitrogen substitution. First, 91.8 g (0.458 mol) of 4,4-diaminodiphenyl ether (hereinafter abbreviated as 4,4′-ODA) is dissolved in 779 g of N, N-dimethylformamide. This solution was kept at 40 ° C. In this solution, 95.0 g (0.436 mol) of pyromellitic dianhydride (hereinafter abbreviated as PMDA) was added and completely dissolved. To this solution, a solution of 5.0 g of PMDA dissolved in 66.5 g of N, N-dimethylformamide was added little by little, and when the viscosity of the solution reached 3100 poise at 23 ° C., the addition was stopped and spinning was performed. The polymer resin solution was obtained. The viscosity of the solution at 23 ° C. was measured with a B-type viscometer at two rotation speeds of 10 rotations / minute and 5 rotations / minute, and the thixo index was calculated from the solution viscosity to be 1.01. Met. The solid content concentration was 18.5%. When a polyimide film was produced from this polyimide resin and the storage elastic modulus was measured, the inflection point was 360 ° C., and it was revealed that it was a non-thermoplastic polyimide resin.

(Examples 1-3)
A spinning experiment was performed using the polyamic acid solution obtained in Synthesis Example 1. The spinning experiment was performed using the same apparatus as in FIG. However, the collecting device 8 was spun in a fixed state, and the obtained polyamic acid fiber aggregate was fired under the following conditions to obtain a fiber aggregate containing non-thermoplastic polyimide fibers having at least a curved portion. . Table 1 shows the spinning conditions and evaluation results of non-thermoplastic polyimide fibers.
The orifice of the discharge nozzle 2 was circular and had 3 holes. The orifice diameter and the discharge amount of the polyamic acid solution were discharged under the conditions shown in Table 1 for spinning. The distance from the orifice of the spinneret 2 to the discharge port of the airflow generator 1 is set at 20 cm, and the airflow 4 is set so that the airflow is perpendicular to the discharge direction of the polyamic acid solution so that the polyamic acid solution is taken up. Spinning was performed. The wind speed from the airflow generator 1 is shown in Table 1 as a result of measuring the wind speed at the point where the polyamic acid fiber intersects. The spun fiber was collected on the collection net 11 after flying 2 m. In this state, collection was performed for 5 hours to obtain an aggregate of polyamic acid fibers in which a part of the solvent remained. The aggregate of polyamic acid fibers was removed from the collection net 11, placed in a metal container, and heated and dried. The heating temperature was drying in an oven at 100 ° C. for 3 minutes, and the temperature was gradually increased from 100 ° C. to 420 ° C. over 1 hour. Firing was performed at 420 ° C. for 5 minutes to obtain an aggregate of polyimide fibers.
Each physical property of the fiber assembly of the obtained non-thermoplastic polyimide fiber was evaluated. The results are summarized in Table 1. Moreover, the electron micrograph of the fiber assembly obtained by spinning is described in FIGS.

(Reference Example 1)
Measurement was carried out under the same conditions for a low-bulk density heat insulating and sound-absorbing material (Johnson Manville, Microlite AA Premium NR, bulk density 5.5 kg / m ³ ) currently used for aircraft applications. If the sound absorption coefficient equivalent to that of this product is shown, it can be judged that it is optimal as a heat insulating and sound absorbing material for aircraft use.

Example of measurement results of dynamic viscoelastic behavior Micrograph of polyimide nonwoven fabric of the invention of the present application (Explanation of curvature) Schematic diagram of the spinning device of the present invention Photo of non-thermoplastic polyimide fiber assembly (Example 1) Photo of non-thermoplastic polyimide fiber assembly (Example 2) Photo of non-thermoplastic polyimide fiber assembly (Example 3)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airflow generator 2 Spinneret 3 Aggregate of polyamic acid fiber 4 Airflow 5 Polyamic acid solution 6 Conveying direction 7 Polyamide fiber aggregate 8 Collection device 9 Heating / drying device 10 Winding device 11 Wire mesh collection device 12 Roll of polyimide fiber aggregate 50 Tangent line to straight line until storage modulus begins to change 51 Tangent line to straight line where storage modulus begins to change 52 Intersection (inflection temperature of storage modulus)

Claims (6)

A heat-insulating / sound-absorbing material comprising a fiber assembly having a non-thermoplastic polyimide fiber having at least a curved portion and a bulk density of 1.0 to 10.0 kg / m ³ ,
The non-thermoplastic polyimide fiber is a heat-insulating / sound-absorbing material obtained by spinning and laminating a polyamic acid solution with an air stream . The heat insulating and sound absorbing material according to claim 1 , wherein the non-thermoplastic polyimide fiber contains at least pyromellitic dianhydride and 4,4-diaminodiphenyl ether as raw materials. The heat insulating / sound absorbing material according to claim 1 or 2 , wherein the fiber assembly is encased in a packaging material for the fiber assembly. Packaging material of the fiber assembly, thermal insulation of claim 3, wherein the polyimide resin, fluorine resin, polyethylene terephthalate resin, polyether ketone resin and a polyether ketone ketone resin in that it consists of at least one resin -Sound absorbing material. Heat insulation and sound absorbing material according to any one of claims 1 to 4 aircraft applications. An aircraft comprising the heat insulating and sound absorbing material according to any one of claims 1 to 5.